bluuebunny/crossref_metadata_2025 huggingface dataset:
Schwann cell spectrins modulate peripheral nerve myelination
Authors: Susuki Keiichiro , Raphael Alya R. , Ogawa Yasuhiro , Stankewich Michael C. , Peles Elior , Talbot William S. , Rasband Matthew N.
Published: April 2011

During peripheral nerve development, Schwann cells ensheathe axons and form myelin to enable rapid and efficient action potential propagation. Although myelination requires profound changes in Schwann cell shape, how neuron–glia interactions converge on the Schwann cell cytoskeleton to induce these changes is unknown. Here, we demonstrate that the submembranous cytoskeletal proteins αII and βII spectrin are polarized in Schwann cells and colocalize with signaling molecules known to modulate myelination in vitro. Silencing expression of these spectrins inhibited myelination in vitro, and remyelination in vivo. Furthermore, myelination was disrupted in motor nerves of zebrafish lacking αII spectrin. Finally, we demonstrate that loss of spectrin significantly reduces both F-actin in the Schwann cell cytoskeleton and the Nectin-like protein, Necl4, at the contact site between Schwann cells and axons. Therefore, we propose αII and βII spectrin in Schwann cells integrate the neuron–glia interactions mediated by membrane proteins into the actin-dependent cytoskeletal rearrangements necessary for myelination.
Structural insight into maintenance methylation by mouse DNA methyltransferase 1 (Dnmt1)
Authors: Takeshita Kohei , Suetake Isao , Yamashita Eiki , Suga Michihiro , Narita Hirotaka , Nakagawa Atsushi , Tajima Shoji
Published: April 2011

Methylation of cytosine in DNA plays a crucial role in development through inheritable gene silencing. The DNA methyltransferase Dnmt1 is responsible for the propagation of methylation patterns to the next generation via its preferential methylation of hemimethylated CpG sites in the genome; however, how Dnmt1 maintains methylation patterns is not fully understood. Here we report the crystal structure of the large fragment (291–1620) of mouse Dnmt1 and its complexes with cofactor
S
-adenosyl-L-methionine and its product
S
-adenosyl-L-homocystein. Notably, in the absence of DNA, the N-terminal domain responsible for targeting Dnmt1 to replication foci is inserted into the DNA-binding pocket, indicating that this domain must be removed for methylation to occur. Upon binding of
S
-adenosyl-L-methionine, the catalytic cysteine residue undergoes a conformation transition to a catalytically competent position. For the recognition of hemimethylated DNA, Dnmt1 is expected to utilize a target recognition domain that overhangs the putative DNA-binding pocket. Taking into considerations the recent report of a shorter fragment structure of Dnmt1 that the CXXC motif positions itself in the catalytic pocket and prevents aberrant de novo methylation, we propose that maintenance methylation is a multistep process accompanied by structural changes.
Dynamic acetylation of all lysine-4 trimethylated histone H3 is evolutionarily conserved and mediated by p300/CBP
Authors: Crump Nicholas T. , Hazzalin Catherine A. , Bowers Erin M. , Alani Rhoda M. , Cole Philip A. , Mahadevan Louis C.
Published: April 2011

Histone modifications are reported to show different behaviors, associations, and functions in different genomic niches and organisms. We show here that rapid, continuous turnover of acetylation specifically targeted to all K4-trimethylated H3 tails (H3K4me3), but not to bulk histone H3 or H3 carrying other methylated lysines, is a common uniform characteristic of chromatin biology in higher eukaryotes, being precisely conserved in human, mouse, and
Drosophila
. Furthermore, dynamic acetylation targeted to H3K4me3 is mediated by the same lysine acetyltransferase, p300/cAMP response element binding (CREB)-binding protein (CBP), in both mouse and fly cells. RNA interference or chemical inhibition of p300/CBP using a newly discovered small molecule inhibitor, C646, blocks dynamic acetylation of H3K4me3 globally in mouse and fly cells, and locally across the promoter and start-site of inducible genes in the mouse, thereby disrupting RNA polymerase II association and the activation of these genes. Thus, rapid dynamic acetylation of all H3K4me3 mediated by p300/CBP is a general, evolutionarily conserved phenomenon playing an essential role in the induction of immediate-early (IE) genes. These studies indicate a more global function of p300/CBP in mediating rapid turnover of acetylation of all H3K4me3 across the nuclei of higher eukaryotes, rather than a tight promoter-restricted function targeted by complex formation with specific transcription factors.
Postmating transcriptional changes in reproductive tracts of con- and heterospecifically mated
Drosophila mojavensis
females
Authors: Bono Jeremy M. , Matzkin Luciano M. , Kelleher Erin S. , Markow Therese A.
Published: April 2011

In internally fertilizing organisms, mating involves a series of highly coordinated molecular interactions between the sexes that occur within the female reproductive tract. In species where females mate multiply, traits involved in postcopulatory interactions are expected to evolve rapidly, potentially leading to postmating-prezygotic (PMPZ) reproductive isolation between diverging populations. Here, we investigate the postmating transcriptional response of the lower reproductive tract of
Drosophila mojavensis
females following copulation with either conspecific or heterospecific (
Drosophila arizonae
) males at three time points postmating. Relatively few genes (15 total) were differentially regulated in the female lower reproductive tract in response to conspecific mating. Heterospecifically mated females exhibited significant perturbations in the expression of the majority of these genes, and also down-regulated transcription of a number of others, including several involved in mitochondrial function. These striking regulatory differences indicate failed postcopulatory molecular interactions between the sexes consistent with the strong PMPZ isolation observed for this cross. We also report the transfer of male accessory-gland protein (Acp) transcripts from males to females during copulation, a finding with potentially broad implications for understanding postcopulatory molecular interactions between the sexes.
Tracking Baltic hypoxia and cod migration over millennia with natural tags
Authors: Limburg Karin E. , Olson Carina , Walther Yvonne , Dale Darren , Slomp Caroline P. , Høie Hans
Published: April 2011

Growing hypoxic and anoxic areas in coastal environments reduce fish habitat, but the interactions and impact on fish in these areas are poorly understood. Using “natural tag” properties of otoliths, we found significant correlations between the extent of Baltic Sea hypoxia and Mn/Ca ratios in regions of cod (
Gadus morhua
) otoliths corresponding to year 1 of life; this is associated with elevated bottom water dissolved manganese that increases with hypoxia. Elevated Mn/Ca ratios were also found in other years of life but with less frequency. We propose that cod exhibiting enhanced Mn/Ca ratios were exposed to dissolved manganese from hypoxia-induced redox dynamics in nursery areas. Neolithic (4500 B.P.) cod otoliths (
n
= 12) had low levels of Mn/Ca ratios, consistent with low hypoxia, but a single otolith dated to the younger Iron Age had a distinct growth band with an elevated Mn/Ca ratio. Sr/Ca patterns reflecting changes in environmental salinity and temperature were similar in both modern and Stone Age otoliths, indicating consistent migration habits across time, and Ba/Sr ratios in modern cod otoliths indicate increasing use of a more saline habitat with age. Using elemental ratios, numerous existing archival collections of otoliths could provide the means to reconstruct hypoxia exposure histories and major patterns of fish movement near “dead zones” globally.
Mutations in lipoprotein lipase that block binding to the endothelial cell transporter GPIHBP1
Authors: Voss Constance V. , Davies Brandon S. J. , Tat Shelly , Gin Peter , Fong Loren G. , Pelletier Christopher , Mottler Charlene D. , Bensadoun André , Beigneux Anne P. , Young Stephen G.
Published: April 2011

GPIHBP1, a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells, shuttles lipoprotein lipase (LPL) from subendothelial spaces to the capillary lumen. An absence of GPIHBP1 prevents the entry of LPL into capillaries, blocking LPL-mediated triglyceride hydrolysis and leading to markedly elevated triglyceride levels in the plasma (i.e., chylomicronemia). Earlier studies have established that chylomicronemia can be caused by LPL mutations that interfere with catalytic activity. We hypothesized that some cases of chylomicronemia might be caused by LPL mutations that interfere with LPL's ability to bind to GPIHBP1. Any such mutation would provide insights into LPL sequences required for GPIHBP1 binding. Here, we report that two
LPL
missense mutations initially identified in patients with chylomicronemia, C418Y and E421K, abolish LPL's ability to bind to GPIHBP1 without interfering with LPL catalytic activity or binding to heparin. Both mutations abolish LPL transport across endothelial cells by GPIHBP1. These findings suggest that sequences downstream from LPL's principal heparin-binding domain (amino acids 403–407) are important for GPIHBP1 binding. In support of this idea, a chicken LPL (cLPL)–specific monoclonal antibody, xCAL 1–11 (epitope, cLPL amino acids 416–435), blocks cLPL binding to GPIHBP1 but not to heparin. Also, changing cLPL residues 421 to 425, 426 to 430, and 431 to 435 to alanine blocks cLPL binding to GPIHBP1 without inhibiting catalytic activity. Together, these data define a mechanism by which LPL mutations could elicit disease and provide insights into LPL sequences required for binding to GPIHBP1.
Rural household income and inequality under the Sloping Land Conversion Program in western China
Authors: Li Jie , Feldman Marcus W. , Li Shuzhuo , Daily Gretchen C.
Published: April 2011

As payment for ecosystem services (PES) programs proliferate globally, assessing their impact upon households’ income and livelihood patterns is critical. The Sloping Land Conversion Program (SLCP) is an exceptional PES program, in terms of its ambitious biophysical and socioeconomic objectives, large geographic scale, numbers of people directly affected, and duration of operation. The SLCP has now operated in the poor mountainous areas in China for 10 y and offers a unique opportunity for policy evaluation. Using survey data on rural households’ livelihoods in the southern mountain area in Zhouzhi County, Shaanxi Province, we carry out a statistical analysis of the effects of PES and other factors on rural household income. We analyze the extent of income inequality and compare the socio-demographic features and household income of households participating in the SLCP with those that did not. Our statistical analysis shows that participation in SLCP has significant positive impacts upon household income, especially for low- and medium-income households; however, participation also has some negative impacts on the low- and medium-income households. Overall, income inequality is less among households participating in the SLCP than among those that do not after 7 y of the PES program. Different income sources have different effects on Gini statistics; in particular, wage income has opposite effects on income inequality for the participating and nonparticipating households. We find, however, that the SLCP has not increased the transfer of labor toward nonfarming activities in the survey site, as the government expected.
Probing the SecYEG translocation pore size with preproteins conjugated with sizable rigid spherical molecules
Authors: Bonardi Francesco , Halza Erik , Walko Martin , Du Plessis François , Nouwen Nico , Feringa Ben L. , Driessen Arnold J. M.
Published: April 2011

Protein translocation in
Escherichia coli
is mediated by the translocase that in its minimal form consists of the protein-conducting channel SecYEG, and the motor protein, SecA. SecYEG forms a narrow pore in the membrane that allows passage of unfolded proteins only. Molecular dynamics simulations suggest that the maximal width of the central pore of SecYEG is limited to

. To access the functional size of the SecYEG pore, the precursor of outer membrane protein A was modified with rigid spherical tetraarylmethane derivatives of different diameters at a unique cysteine residue. SecYEG allowed the unrestricted passage of the precursor of outer membrane protein A conjugates carrying tetraarylmethanes with diameters up to

, whereas a

sized molecule blocked the translocation pore. Translocation of the protein-organic molecule hybrids was strictly proton motive force-dependent and occurred at a single pore. With an average diameter of an unfolded polypeptide chain of

, the pore accommodates structures of at least

, which is vastly larger than the predicted maximal width of a single pore by molecular dynamics simulations.
Isoform-specific monobody inhibitors of small ubiquitin-related modifiers engineered using structure-guided library design
Authors: Gilbreth Ryan N. , Truong Khue , Madu Ikenna , Koide Akiko , Wojcik John B. , Li Nan-Sheng , Piccirilli Joseph A. , Chen Yuan , Koide Shohei
Published: April 2011

Discriminating closely related molecules remains a major challenge in the engineering of binding proteins and inhibitors. Here we report the development of highly selective inhibitors of small ubiquitin-related modifier (SUMO) family proteins. SUMOylation is involved in the regulation of diverse cellular processes. Functional differences between two major SUMO isoforms in humans, SUMO1 and SUMO2/3, are thought to arise from distinct interactions mediated by each isoform with other proteins containing SUMO-interacting motifs (SIMs). However, the roles of such isoform-specific interactions are largely uncharacterized due in part to the difficulty in generating high-affinity, isoform-specific inhibitors of SUMO/SIM interactions. We first determined the crystal structure of a “monobody,” a designed binding protein based on the fibronectin type III scaffold, bound to the yeast homolog of SUMO. This structure illustrated a mechanism by which monobodies bind to the highly conserved SIM-binding site while discriminating individual SUMO isoforms. Based on this structure, we designed a SUMO-targeted library from which we obtained monobodies that bound to the SIM-binding site of human SUMO1 with
K
d
values of approximately 100 nM but bound to SUMO2 400 times more weakly. The monobodies inhibited SUMO1/SIM interactions and, unexpectedly, also inhibited SUMO1 conjugation. These high-affinity and isoform-specific inhibitors will enhance mechanistic and cellular investigations of SUMO biology.
Down-regulation of homeobox genes
MEIS1
and
HOXA
in
MLL
-rearranged acute leukemia impairs engraftment and reduces proliferation
Authors: Orlovsky Kira , Kalinkovich Alexander , Rozovskaia Tanya , Shezen Elias , Itkin Tomer , Alder Hansjuerg , Ozer Hatice Gulcin , Carramusa Letizia , Avigdor Abraham , Volinia Stefano , Buchberg Arthur , Mazo Alex , Kollet Orit , Largman Corey , Croce Carlo M. , Nakamura Tatsuya , Lapidot Tsvee , Canaani Eli
Published: April 2011

Rearrangements of the
MLL (ALL1)
gene are very common in acute infant and therapy-associated leukemias. The rearrangements underlie the generation of
MLL
fusion proteins acting as potent oncogenes. Several most consistently up-regulated targets of MLL fusions,
MEIS1
,
HOXA7, HOXA9,
and
HOXA10
are functionally related and have been implicated in other types of leukemias. Each of the four genes was knocked down separately in the human precursor B-cell leukemic line RS4;11 expressing MLL-AF4. The mutant and control cells were compared for engraftment in NOD/SCID mice. Engraftment of all mutants into the bone marrow (BM) was impaired. Although homing was similar, colonization by the knockdown cells was slowed. Initially, both types of cells were confined to the trabecular area; this was followed by a rapid spread of the WT cells to the compact bone area, contrasted with a significantly slower process for the mutants. In vitro and in vivo BrdU incorporation experiments indicated reduced proliferation of the mutant cells. In addition, the CXCR4/SDF-1 axis was hampered, as evidenced by reduced migration toward an SDF-1 gradient and loss of SDF-1–augmented proliferation in culture. The very similar phenotype shared by all mutant lines implies that all four genes are involved and required for expansion of MLL-AF4 associated leukemic cells in mice, and down-regulation of any of them is not compensated by the others.
Fibroblast growth factor-2 (FGF2) augmentation early in life alters hippocampal development and rescues the anxiety phenotype in vulnerable animals
Authors: Turner Cortney A. , Clinton Sarah M. , Thompson Robert C. , Watson Stanley J. , Akil Huda
Published: April 2011

Individuals with mood disorders exhibit alterations in the fibroblast growth factor system, including reduced hippocampal fibroblast growth factor-2 (FGF2). It is difficult, however, to pinpoint whether these alterations are a cause or consequence of the disorder. The present study asks whether FGF2 administered the day after birth has long-lasting effects on hippocampal development and emotionality. We show that early-life FGF2 shifts the pace of neurogenesis, with an early acceleration around weaning followed by a deceleration in adulthood. This, in turn, results in a denser dentate gyrus with more neurons. To assess the impact of early-life FGF2 on emotionality, we use rats selectively bred for differences in locomotor response to novelty. Selectively bred low-responder (bLR) rats show low levels of novelty-induced locomotion and exhibit high levels of anxiety- and depression-like behavior compared with their selectively bred high-responder counterparts. Early-life FGF2 decreased anxiety-like behavior in highly anxious bLRs without altering other behaviors and without affecting high-responder rats. Laser capture microscopy of the dentate gyrus followed by microarray analysis revealed genes that were differentially expressed in bLRs exposed to early-life FGF2 vs. vehicle-treated bLRs. Some of the differentially expressed genes that have been positively associated with anxiety were down-regulated, whereas genes that promote cell survival were up-regulated. Overall, these results show a key role for FGF2 in the developmental trajectory of the hippocampus as well as the modulation of anxiety-like behavior in adulthood, and they point to potential downstream targets for the treatment of anxiety disorders.
Polycystin-1 regulates STAT activity by a dual mechanism
Authors: Talbot Jeffrey J. , Shillingford Jonathan M. , Vasanth Shivakumar , Doerr Nicholas , Mukherjee Sambuddho , Kinter Mike T. , Watnick Terry , Weimbs Thomas
Published: April 2011

Mutations in polycystin-1 (PC1) lead to autosomal-dominant polycystic kidney disease (ADPKD), a leading cause of renal failure for which no treatment is available. PC1 is an integral membrane protein, which has been implicated in the regulation of multiple signaling pathways including the JAK/STAT pathway. Here we show that membrane-anchored PC1 activates STAT3 in a JAK2-dependent manner, leading to tyrosine phosphorylation and transcriptional activity. The C-terminal cytoplasmic tail of PC1 can undergo proteolytic cleavage and nuclear translocation. Tail-cleavage abolishes the ability of PC1 to directly activate STAT3 but the cleaved PC1 tail now coactivates STAT3 in a mechanism requiring STAT phosphorylation by cytokines or growth factors. This leads to an exaggerated cytokine response. Hence, PC1 can regulate STAT activity by a dual mechanism. In ADPKD kidneys PC1 tail fragments are overexpressed, including a unique ∼15-kDa fragment (P15). STAT3 is strongly activated in cyst-lining epithelial cells in human ADPKD, and orthologous and nonorthologous polycystic mouse models. STAT3 is also activated in developing, postnatal kidneys but inactivated in adult kidneys. These results indicate that STAT3 signaling is regulated by PC1 and is a driving factor for renal epithelial proliferation during normal renal development and during cyst growth.
The catalytic domain of all eukaryotic cut-and-paste transposase superfamilies
Authors: Yuan Yao-Wu , Wessler Susan R.
Published: April 2011

Cut-and-paste DNA transposable elements are major components of eukaryotic genomes and are grouped into superfamilies (e.g.,
hAT
,
P
) based on sequence similarity of the element-encoded transposase. The transposases from several superfamilies possess a protein domain containing an acidic amino acid triad (DDE or DDD) that catalyzes the “cut and paste” transposition reaction. However, it was unclear whether this domain was shared by the transposases from all superfamilies. Through multiple-alignment of transposase sequences from a diverse collection of previously identified and recently annotated elements from a wide range of organisms, we identified the putative DDE/D triad for all superfamilies. Furthermore, we identified additional highly conserved amino acid residues or motifs within the DDE/D domain that together form a “signature string” that is specific to each superfamily. These conserved residues or motifs were exploited as phylogenetic characters to infer evolutionary relationships among all superfamilies. The phylogenetic analysis revealed three major groups that were not previously discerned and led us to revise the classification of several currently recognized superfamilies. Taking the data together, this study suggests that all eukaryotic cut-and-paste transposable element superfamilies have a common evolutionary origin and establishes a phylogenetic framework for all future cut-and-paste transposase comparisons.
Vaccine adjuvants aluminum and monophosphoryl lipid A provide distinct signals to generate protective cytotoxic memory CD8 T cells
Authors: MacLeod Megan K. L. , McKee Amy S. , David Alexandria , Wang Jieru , Mason Robert , Kappler John W. , Marrack Philippa
Published: April 2011

Vaccines can greatly reduce the spread of and deaths from many infectious diseases. However, many infections have no successful vaccines. Better understanding of the generation of protective CD8 memory T cells by vaccination is essential for the rational design of new vaccines that aim to prime cellular immune responses. Here we demonstrate that the combination of two adjuvants that are currently licensed for use in humans can be used to prime long-lived memory CD8 T cells that protect mice from viral challenge. The universally used adjuvant, aluminum salts, primed long-lived memory CD8 T cells; however, effective cytotoxic T-cell differentiation occurred only in the presence of an additional adjuvant, monophosphoryl lipid A (MPL). MPL-induced IL-6 was required for cytotoxic differentiation. The IL-6 acted by inducing granzyme B production and reducing expression of inhibitory molecule PD1 on the surface of the primed CD8 T cells. CD8 memory T cells generated by antigen delivered with both aluminum salts and MPL provided significant protection from influenza A challenge. These adjuvants could be used in human vaccines to prime protective memory CD8 T cells.
X-linked cholestasis in mouse due to mutations of the P4-ATPase ATP11C
Authors: Siggs Owen M. , Schnabl Bernd , Webb Bill , Beutler Bruce
Published: April 2011

Transporters at the hepatic canalicular membrane are essential for the formation of bile and the prevention of cholestatic liver disease. One such example is ATP8B1, a P4-type ATPase disrupted in three inherited forms of intrahepatic cholestasis. Mutation of the X-linked mouse gene
Atp11c
, which encodes a paralogous P4-type ATPase, precludes B-cell development in the adult bone marrow, but also causes hyperbilirubinemia. Here we explore this hyperbilirubinemia in two independent
Atp11c
mutant mouse lines, and find that it originates from an effect on nonhematopoietic cells. Liver function tests and histology revealed only minor pathology, although cholic acid was elevated in the serum of mutant mice, and became toxic to mutant mice when given as a dietary supplement. The majority of homozygous mutant females also died of dystocia in a maternal genotype-specific manner. ATP11C therefore represents a multifunctional transporter, essential for adult B-cell development, the prevention of intrahepatic cholestasis, and parturition, and is a new candidate for genetically undiagnosed cases of cholestasis and dystocia in humans.
Antidepressant effects of selective serotonin reuptake inhibitors (SSRIs) are attenuated by antiinflammatory drugs in mice and humans
Authors: Warner-Schmidt Jennifer L. , Vanover Kimberly E. , Chen Emily Y. , Marshall John J. , Greengard Paul
Published: April 2011

Antiinflammatory drugs achieve their therapeutic actions at least in part by regulation of cytokine formation. A “cytokine hypothesis” of depression is supported by the observation that depressed individuals have elevated plasma levels of certain cytokines compared with healthy controls. Here we investigated a possible interaction between antidepressant agents and antiinflammatory agents on antidepressant-induced behaviors and on p11, a biochemical marker of depressive-like states and antidepressant responses. We found that widely used antiinflammatory drugs antagonize both biochemical and behavioral responses to selective serotonin reuptake inhibitors (SSRIs). In contrast to the levels detected in serum, we found that frontal cortical levels of certain cytokines (e.g., TNFα and IFNγ) were increased by serotonergic antidepressants and that these effects were inhibited by antiinflammatory agents. The antagonistic effect of antiinflammatory agents on antidepressant-induced behaviors was confirmed by analysis of a dataset from a large-scale real-world human study, “sequenced treatment alternatives to relieve depression” (STAR*D), underscoring the clinical significance of our findings. Our data indicate that clinicians should carefully balance the therapeutic benefits of antiinflammatory agents versus the potentially negative consequences of antagonizing the therapeutic efficacy of antidepressant agents in patients suffering from depression.
EBV nuclear antigen EBNALP dismisses transcription repressors NCoR and RBPJ from enhancers and EBNA2 increases NCoR-deficient RBPJ DNA binding
Authors: Portal Daniel , Zhao Bo , Calderwood Michael A. , Sommermann Thomas , Johannsen Eric , Kieff Elliott
Published: April 2011

EBV nuclear antigen 2 (EBNA2) and EBV nuclear antigen LP (EBNALP) are critical for B-lymphocyte transformation to lymphoblastoid cell lines (LCLs). EBNA2 activates transcription through recombination signal-binding immunoglobulin κJ region (RBPJ), a transcription factor associated with NCoR repressive complexes, and EBNALP is implicated in repressor relocalization. EBNALP coactivation with EBNA2 was found to dominate over NCoR repression. EBNALP associated with NCoR and dismissed NCoR, NCoR and RBPJ, or NCoR, RBPJ, and EBNA2 from matrix-associated deacetylase (MAD) bodies. In non–EBV-infected BJAB B lymphoma cells that stably express EBNA2, EBNALP, or EBNA2 and EBNALP, EBNALP was associated with hairy and enhancer of split 1 (
hes1
),
cd21
,
cd23,
and arginine and glutamate-rich 1 (
arglu1
) enhancer or promoter DNA and was associated minimally with coding DNA. With the exception of RBPJ at the
arglu1
enhancer, NCoR and RBPJ were significantly decreased at enhancer and promoter sites in EBNALP or EBNA2 and EBNALP BJAB cells. EBNA2 DNA association was unaffected by EBNALP, and EBNALP was unaffected by EBNA2. EBNA2 markedly increased RBPJ at enhancer sites without increasing NCoR. EBNALP further increased
hes1
and
arglu1
RNA levels with EBNA2 but did not further increase
cd21
or
cd23
RNA levels. EBNALP in which the 45 C-terminal residues critical for transformation and transcriptional activation were deleted associated with NCoR but was deficient in dismissing NCoR from MAD bodies and from enhancer and promoter sites. These data strongly support a model in which EBNA2 association with NCoR–deficient RBPJ enhances transcription and EBNALP dismisses NCoR and RBPJ repressive complexes from enhancers to coactivate
hes1
and
arglu1
but not
cd21
or
cd23
.
Function of the DEMETER DNA glycosylase in the
Arabidopsis thaliana
male gametophyte
Authors: Schoft Vera K. , Chumak Nina , Choi Yeonhee , Hannon Mike , Garcia-Aguilar Marcelina , Machlicova Adriana , Slusarz Lucyna , Mosiolek Magdalena , Park Jin-Sup , Park Guen Tae , Fischer Robert L. , Tamaru Hisashi
Published: April 2011

In double fertilization, the vegetative cell of the male gametophyte (pollen) germinates and forms a pollen tube that brings to the female gametophyte two sperm cells that fertilize the egg and central cell to form the embryo and endosperm, respectively. The 5-methylcytosine DNA glycosylase DEMETER (DME), expressed in the central cell, is required for maternal allele demethylation and gene imprinting in the endosperm. By contrast, little is known about the function of DME in the male gametophyte. Here we show that reduced transmission of the paternal mutant
dme
allele in certain ecotypes reflects, at least in part, defective pollen germination.
DME
RNA is detected in pollen, but not in isolated sperm cells, suggesting that
DME
is expressed in the vegetative cell. Bisulfite sequencing experiments show that imprinted genes (
MEA
and
FWA
) and a repetitive element (
Mu1a
) are hypomethylated in the vegetative cell genome compared with the sperm genome, which is a process that requires DME. Moreover, we show that
MEA
and
FWA
RNA are detectable in pollen, but not in isolated sperm cells, suggesting that their expression occurs primarily in the vegetative cell. These results suggest that DME is active and demethylates similar genes and transposons in the genomes of the vegetative and central cells in the male and female gametophytes, respectively. Although the genome of the vegetative cell does not participate in double fertilization, its DME-mediated demethylation is important for male fertility and may contribute to the reconfiguration of the methylation landscape that occurs in the vegetative cell genome.
Role of autonomous androgen receptor signaling in prostate cancer initiation is dichotomous and depends on the oncogenic signal
Authors: Memarzadeh Sanaz , Cai Houjian , Janzen Deanna M. , Xin Li , Lukacs Rita , Riedinger Mireille , Zong Yang , DeGendt Karel , Verhoeven Guido , Huang Jiaoti , Witte Owen N.
Published: April 2011

The steroid hormone signaling axis is thought to play a central role in initiation and progression of many hormonally regulated epithelial tumors. It is unclear whether all cancer-initiating signals depend on an intact hormone receptor signaling machinery. To ascertain whether cell autonomous androgen receptor (AR) is essential for initiation of prostate intraepithelial neoplasia (PIN), the response of AR-null prostate epithelia to paracrine and cell autonomous oncogenic signals was assessed in vivo by using the prostate regeneration model system. Epithelial-specific loss of AR blocked paracrine FGF10-induced PIN, whereas the add back of exogenous AR restored this response. In contrast, PIN initiated by cell-autonomous, chronic-activated AKT developed independent of epithelial AR signaling. Our findings demonstrate a selective role for AR in the initiation of PIN, dependent on the signaling pathways driving tumor formation. Insights into the role of hormone receptor signaling in the initiation of epithelial tumors may help define this axis as a target for chemoprevention of carcinomas.
Processing Temporary Syntactic Ambiguity: The Effect of Contextual Bias
Authors: Mohamed Mohamed Taha , Clifton Charles
Published: April 2011

This paper reports two experiments using sentences with a temporary ambiguity between a direct object and a sentence complement analysis that is resolved toward the normally preferred direct object analysis. Postverbal noun phrases in these sentences could be ambiguously attached as either a direct object or the subject of a sentence complement, whereas in unambiguous versions of the sentences the subcategorization of the verb forced the direct object interpretation. Participants read these sentences in relatively long paragraph contexts, where the context supported the direct object analysis (“preferred”), supported the sentence complement analysis (“unpreferred”), or provided conflicting evidence about both analyses (“conflicting”). Self-paced reading times for ambiguous postverbal noun phrases were almost equivalent to the reading times of their unambiguous counterparts, even in unpreferred and conflicted context conditions. However, time to read a following region, which forced the direct object interpretation, was affected by the interaction of verb subcategorization ambiguity and contextual support. The full pattern of results do not fit well with either an unelaborated single-analysis (“garden path”) model or a competitive constraint-satisfaction model, but are consistent with a race model in which multiple factors affect the speed of constructing a single initial analysis.
Viral protein targeting to the cortical endoplasmic reticulum is required for cell–cell spreading in plants
Authors: Wu Chih-Hang , Lee Shu-Chuan , Wang Chao-Wen
Published: April 2011

Many plant RNA viruses use their nonstructural proteins to target and move through the cortical endoplasmic reticulum (ER) tubules within the plant intercellular junction for cell-to-cell spreading. Most of these proteins, including the triple-gene-block 3 protein (TGBp3) of Potexvirus, are ER membrane proteins. We previously showed that TGBp3 of the Bamboo mosaic potexvirus partitions into tubular subdomains of the ER in both yeast and plants, but the mechanism and physiological significance of this localization is unclear. Here, we demonstrate that a sorting signal present in TGBp3 is necessary and sufficient for its oligomerization and for targeting integral membrane proteins into puncta within curved ER tubules. Mutations in the TGBp3 sorting signal impair viral spread, and plants infected with viruses harboring these mutants were either asymptomatic or had reduced symptoms. Thus, we propose that Potexvirus use the sorting signal in TGBp3 to target infectious viral derivatives to cortical ER tubules for transmission through the intercellular junctions in plants.
RBM4 down-regulates PTB and antagonizes its activity in muscle cell–specific alternative splicing
Authors: Lin Jung-Chun , Tarn Woan-Yuh
Published: April 2011

Alternative splicing contributes largely to cell differentiation and functional specification. We previously reported that the RNA-binding protein RBM4 antagonizes the activity of splicing factor PTB to modulate muscle cell–specific exon selection of α-tropomyosin. Here we show that down-regulation of PTB and its neuronal analogue nPTB during muscle cell differentiation may involve alternative splicing-coupled nonsense-mediated mRNA decay. RBM4 regulates PTB/nPTB expression by activating exon skipping of their transcripts during myogenesis. Moreover, RBM4 and PTB target a common set of transcripts that undergo muscle cell–specific alternative splicing. Overexpression of RBM4 invariably promoted expression of muscle cell–specific isoforms, which recapitulated in vivo alternative splicing changes during muscle differentiation, whereas PTB acted oppositely to RBM4 in expression of mRNA isoforms specific for late-stage differentiation. Therefore, RBM4 may synergize its effect on muscle cell–specific alternative splicing by down-regulating PTB expression and antagonizing the activity of PTB in exon selection, which highlights a hierarchical role for RBM4 in a splicing cascade that regulates myogenesis.
Hax1 regulates neutrophil adhesion and motility through RhoA
Authors: Cavnar Peter J. , Berthier Erwin , Beebe David J. , Huttenlocher Anna
Published: April 2011

Kostmann disease is an inherited severe congenital neutropenia syndrome associated with loss-of-function mutations in an adaptor protein HS1-associated protein X-1 (Hax1). How Hax1 regulates neutrophil function remains largely unknown. In this paper, we use ribonucleic acid interference to deplete Hax1 in the neutrophil-like cell line PLB-985 and identify Hax1 as a negative regulator of integrin-mediated adhesion and chemotaxis. Using microfluidics, we show that depletion of Hax1 impairs neutrophil uropod detachment and directed migration. Hax1-deficient cells also display increased integrin-mediated adhesion and reduced RhoA activity. Moreover, depletion of RhoA induces increased neutrophil adhesion and impaired migration, suggesting that Hax1 regulates neutrophil adhesion and chemotaxis through RhoA. Accordingly, activation of RhoA is sufficient to rescue adhesion of Hax1-deficient neutrophils. Together, our findings identify Hax1 as a novel regulator of neutrophil uropod detachment and chemotaxis through RhoA.
Targeting of the SUN protein Mps3 to the inner nuclear membrane by the histone variant H2A.Z
Authors: Gardner Jennifer M. , Smoyer Christine J. , Stensrud Elizabeth S. , Alexander Richard , Gogol Madelaine , Wiegraebe Winfried , Jaspersen Sue L.
Published: April 2011

Understanding the relationship between chromatin and proteins at the nuclear periphery, such as the conserved SUN family of inner nuclear membrane (INM) proteins, is necessary to elucidate how three-dimensional nuclear architecture is established and maintained. We found that the budding yeast SUN protein Mps3 directly binds to the histone variant H2A.Z but not other histones. Biochemical and genetic data indicate that the interaction between Mps3 and H2A.Z requires the Mps3 N-terminal acidic domain and unique sequences in the H2A.Z N terminus and histone-fold domain. Analysis of binding-defective mutants showed that the Mps3–H2A.Z interaction is not essential for any previously described role for either protein in nuclear organization, and multiple lines of evidence suggest that Mps3–H2A.Z binding occurs independently of H2A.Z incorporation into chromatin. We demonstrate that H2A.Z is required to target a soluble Mps3 fragment to the nucleus and to localize full-length Mps3 in the INM, indicating that H2A.Z has a novel chromatin-independent function in INM targeting of SUN proteins.
Essential role of peripheral node addressin in lymphocyte homing to nasal-associated lymphoid tissues and allergic immune responses
Authors: Ohmichi Yukari , Hirakawa Jotaro , Imai Yasuyuki , Fukuda Minoru , Kawashima Hiroto
Published: April 2011

Nasal-associated lymphoid tissue (NALT) is a mucosal immune tissue that provides immune responses against inhaled antigens. Lymphocyte homing to NALT is mediated by specific interactions between lymphocytes and high endothelial venules (HEVs) in NALT. In contrast to HEVs in other mucosal lymphoid tissues, NALT HEVs strongly express peripheral node addressins (PNAds) that bear sulfated glycans recognized by the monoclonal antibody MECA-79. We investigated the role of PNAd in lymphocyte homing to NALT using sulfotransferase N-acetylglucosamine-6-O-sulfotransferase (GlcNAc6ST) 1 and GlcNAc6ST-2 double knockout (DKO) mice. The expression of PNAd in NALT HEVs was eliminated in DKO mice. Short-term homing assays indicated that lymphocyte homing to NALT was diminished by 90% in DKO mice. Production of antigen-specific IgE and the number of sneezes in response to nasally administered ovalbumin were also substantially diminished. Consistently, the NALT of DKO mice showed reduced production of IL-4 and increased production of IL-10 together with an increase in CD4+CD25+ regulatory T cells (Treg cells). Compared with the homing of CD4+CD25− conventional T cells, the homing of CD4+CD25+ Treg cells to NALT was less dependent on the L-selectin–PNAd interaction but was partially dependent on PSGL-1 (P-selectin glycoprotein ligand 1) and CD44. These results demonstrate that PNAd is essential for lymphocyte homing to NALT and nasal allergic responses.
Distinct MHC class I–dependent NK cell–activating receptors control cytomegalovirus infection in different mouse strains
Authors: Pyzik Michał , Charbonneau Benoit , Gendron-Pontbriand Eve-Marie , Babić Marina , Krmpotić Astrid , Jonjić Stipan , Vidal Silvia M.
Published: April 2011

Recognition of mouse cytomegalovirus (MCMV)–infected cells by activating NK cell receptors was first described in the context of Ly49H, which confers resistance to C57BL/6 mice. We investigated the ability of other activating Ly49 receptors to recognize MCMV-infected cells in mice from various H-2 backgrounds. We observed that Ly49P1 from NOD/Ltj mice, Ly49L from BALB mice, and Ly49D2 from PWK/Pas mice respond to MCMV-infected cells in the context of H-2Dk and the viral protein m04/gp34. Recognition was also seen in the H-2d and/or H-2f contexts, depending on the Ly49 receptor examined, but never in H-2b. Furthermore, BALB.K (H-2k) mice showed reduced viral loads compared with their H-2d or H-2b congenic partners, a reduction which was dependent on interferon γ secretion by Ly49L+ NK cells early after infection. Adoptive transfer of Ly49L+, but not Ly49L−, NK cells significantly increased resistance against MCMV infection in neonate BALB.K mice. These results suggest that multiple activating Ly49 receptors participate in H-2–dependent recognition of MCMV infection, providing a common mechanism of NK cell–mediated resistance against viral infection.
The lineage-defining factors T-bet and Bcl-6 collaborate to regulate Th1 gene expression patterns
Authors: Oestreich Kenneth J. , Huang Albert C. , Weinmann Amy S.
Published: April 2011

The T-box transcription factor T-bet is important for the differentiation of naive CD4+ T helper cells (Th cells) into the Th1 phenotype. Much is known about T-bet’s role as a transcriptional activator, but less is known about the mechanisms by which T-bet functionally represses alternative Th cell genetic programs. In this study, we first identify Socs1, Socs3, and Tcf7 (TCF-1) as gene targets that are negatively regulated by T-bet. Significantly, T-bet’s role in the repression of these genes is through a direct interaction with their promoters. Consistent with this, we identified two T-bet DNA-binding elements in the Socs1 promoter that are functionally used to down-regulate transcription in primary Th1 cells. Importantly, T-bet’s novel role in transcriptional repression is because of its ability to physically associate with, and functionally recruit, the transcriptional repressor Bcl-6 to a subset of promoters. Furthermore, T-bet functionally recruits Bcl-6 to the Ifng locus in late stages of Th1 differentiation to repress its activity, possibly to prevent the overproduction of IFN-γ, which could result in autoimmunity. Collectively, these data establish a novel mechanism for T-bet–mediated gene repression in which two lineage-defining transcription factors, one a classical activator and one a repressor, collaborate to promote and properly regulate Th1 development.
p53 regulates epithelial–mesenchymal transition through microRNAs targeting ZEB1 and ZEB2
Authors: Kim Taewan , Veronese Angelo , Pichiorri Flavia , Lee Tae Jin , Jeon Young-Jun , Volinia Stefano , Pineau Pascal , Marchio Agnès , Palatini Jeff , Suh Sung-Suk , Alder Hansjuerg , Liu Chang–Gong , Dejean Anne , Croce Carlo M.
Published: April 2011

p53 suppresses tumor progression and metastasis. Epithelial–mesenchymal transition (EMT) is a key process in tumor progression and metastasis. The transcription factors ZEB1 and ZEB2 promote EMT. Here, we show that p53 suppresses EMT by repressing expression of ZEB1 and ZEB2. By profiling 92 primary hepatocellular carcinomas (HCCs) and 9 HCC cell lines, we found that p53 up-regulates microRNAs (miRNAs), including miR-200 and miR-192 family members. The miR-200 family members transactivated by p53 then repress ZEB1/2 expression. p53-regulated miR-192 family members also repress ZEB2 expression. Inhibition or overexpression of the miRNAs affects p53-regulated EMT by altering ZEB1 and ZEB2 expression. Our findings indicate that p53 can regulate EMT, and that p53-regulated miRNAs are critical mediators of p53-regulated EMT.
Isoperimetric surfaces with boundary
Authors: Dorff Rebecca , Johnson Drew , Lawlor Gary , Sampson Donald
Published: April 2011

We prove that many common combinations of soap films and soap bubbles that result from dipping polyhedral wire frames in a soap solution are minimizing with respect to their boundary and bubble volume. This can be thought of as a combination of the Plateau problem of least area for surfaces spanning a given boundary and the isoperimetric problem of least area for surfaces enclosing a given volume. Proof is given in arbitrary dimension using a combination of the mapping of Gromov, after Knothe, and the paired calibrations of Lawlor and Morgan.
Embedding dendriform algebra into its universal enveloping Rota-Baxter algebra
Authors: Chen Yuqun , Mo Qiuhui
Published: April 2011

In this paper, by using Gröbner-Shirshov bases for Rota-Baxter algebras, we prove that every dendriform algebra over a field of characteristic 0 can be embedded into its universal enveloping Rota-Baxter algebra.
First Report of Powdery Mildew on Ruth's Golden Aster (Pityopsis ruthii) Caused by Golovinomyces cichoracearum (Erysiphe cichoracearum)
Authors: Trigiano R. N. , Dattilo A. J. , Wadl P. A.
Published: April 2011

Ruth's golden aster (Pityopsis ruthii (Small) Small: Asteraceae) is an endangered, herbaceous perennial that occurs only at a few sites along small reaches of the Hiwassee and Ocoee rivers in Polk County, Tennessee. As part of a planned restoration program, Ruth's golden aster has been micropropagated in vitro and acclimatized to greenhouse conditions. In February 2011, several established plants in a greenhouse in Knoxville, TN exhibited signs and symptoms of powdery mildew including growth of white mycelium and conidiophores on the adaxial surface of leaves and slight curling upward of leaf margins. Mycelium was superficial and nipple-shaped appressoria were present. Mycelia, conidiophores, and conidia were removed from several leaves, mounted in water, and examined microscopically. Cylindrical to ovoid conidia (n = 100) lacking fibrosin bodies were borne in chains and had a mean length of 32.0 μm (19.2 to 38.7 μm) and width of 14.9 μm (6.3 to 21.2 μm). The description and dimension of the conidia agreed well with that provided for Golovinomyces cichoracearum (Erysiphe cichoracearum) reported on Coreopsis spp. (1,3) and Cirsium arvense (creeping thistle) (2). The teleomorph was not observed. Total genomic DNA was extracted from infected leaves, amplified with ITS1 and ITS4 primers for the 18S rRNA subunit (4), and visualized on a 2% ethidium bromide agarose gel. An amplicon of fungal origin, approximately 550 bp and smaller than the approximately 700-bp plant ITS amplicon, was excised, purified, and then sequenced. This sequence was deposited in GenBank (Accession No. JF779687) and was 99% identical to two G. cichoracearum accessions (Nos. AB77627 and AB77625). Infected leaves were rubbed on leaves of four healthy plants and healthy leaves were rubbed onto other healthy leaves of two additional plants as controls in the greenhouse. Signs of powdery mildew developed on those plants inoculated with infected leaves after 7 to 10 days and the morphology of the fungus was identical to our previous description. To our knowledge, this is the first report of G. cichoracearum (E. cichoracearum) infecting Ruth's golden aster. We are not aware of the disease occurring in wild populations of the plant, but it does impact the production of micropropagated plants in the greenhouse.

References: (1) D. A. Glawe et al. Online publication. doi:10.1094/PHP-2006-0405-01-BR. Plant Health Progress, 2006. (2) G. Newcombe and C. Nischwitz. Plant Dis. 88:312, 2004. (3) T. E. Seijo et al. Online publication. doi: 10.1094/PHP-2006-1214-01-BR. Plant Health Progress, 2006. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press Inc, New York, 1990.