bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mga2p Processing by Hypoxia and Unsaturated Fatty Acids in
Saccharomyces cerevisiae
: Impact on LORE-Dependent Gene Expression
Authors: Jiang Yide , Vasconcelles Michael J. , Wretzel Sharon , Light Anne , Gilooly Laura , McDaid Kevin , Oh Chan-Seok , Martin Charles E. , Goldberg Mark A. 
Published: December 2002

ABSTRACT

In
Saccharomyces cerevisiae
,
OLE1
encodes a Δ9 fatty acid desaturase, an enzyme that plays a critical role in maintaining the correct ratio of saturated to monounsaturated fatty acids in the cell membrane. Previous studies have demonstrated that (i)
OLE1
expression is repressed by unsaturated fatty acids (UFAs) and induced by low oxygen tension, (ii) a component of this regulation is mediated through the same low oxygen response element (LORE) in the
OLE1
promoter, and (iii) Mga2p is involved in LORE-dependent hypoxic induction of
OLE1
. We now report that LORE-
CYC1
basal promoter-
lacZ
fusion reporter assays demonstrate that UFAs repress the reporter expression under hypoxic conditions in a dose-dependent manner via LORE. Electrophoretic mobility shift assays show that UFAs repress the hypoxia-induced complex formation with LORE. Studies with a construct encoding a truncated form of Mga2p support the hypothesis that both hypoxia and UFA signals affect the processing of Mga2p and the UFA repression of
OLE1
hypoxic induction is mediated through Mga2p. Data from Western blot assays provide evidence that under normoxic conditions, Mga2p processing produces approximately equimolar levels of the membrane-bound and processed forms and is unaffected by UFAs. Hypoxic induction of
OLE1
, however, is associated with increased processing of the protein, resulting in an approximately fivefold increase in the soluble active form that is counteracted by exposure of the cells to unsaturated fatty acids. Data from this study suggest that the Mga2p-LORE interaction plays an important role in
OLE1
expression under both normoxic and hypoxic conditions.
Rub1p Processing by Yuh1p Is Required for Wild-Type Levels of Rub1p Conjugation to Cdc53p
Authors: Linghu Bolan , Callis Judy , Goebl Mark G. 
Published: December 2002

ABSTRACT

In
Saccharomyces cerevisiae
, Rub1p, like ubiquitin, is conjugated to proteins. Before protein conjugation, the carboxyl-terminal asparagine residue of Rub1p is removed. Rub1p conjugation is dependent on the carboxyl-terminal processing enzyme Yuh1p, whereas Rub1p lacking the asparagine residue is conjugated without Yuh1p. Thus, Yuh1p is the major processing enzyme for Rub1p.
Two Copies of
mthmg1
, Encoding a Novel Mitochondrial HMG-Like Protein, Delay Accumulation of Mitochondrial DNA Deletions in
Podospora anserina
Authors: Dequard-Chablat Michelle , Alland Cynthia 
Published: December 2002

ABSTRACT

In the filamentous fungus
Podospora anserina
, two degenerative processes which result in growth arrest are associated with mitochondrial genome (mitochondrial DNA [mtDNA]) instability. Senescence is correlated with mtDNA rearrangements and amplification of specific regions (senDNAs). Premature death syndrome is characterized by the accumulation of specific mtDNA deletions. This accumulation is due to indirect effects of the
AS1-4
mutation, which alters a cytosolic ribosomal protein gene. The
mthmg1
gene has been identified as a double-copy suppressor of premature death. It greatly delays premature death and the accumulation of deletions when it is present in two copies in an
AS1-4
context. The duplication of
mthmg1
has no significant effect on the wild-type life span or on senDNA patterns. In an
AS1
+
context, deletion of the
mthmg1
gene alters germination, growth, and fertility and reduces the life span. The
Δmthmg1
senescent strains display a particular senDNA pattern. This deletion is lethal in an
AS1-4
context. According to its physical properties (very basic protein with putative mitochondrial targeting sequence and HMG-type DNA-binding domains) and the cellular localization of an mtHMG1-green fluorescent protein fusion, mtHMG1 appears to be a mitochondrial protein possibly associated with mtDNA. It is noteworthy that it is the first example of a protein combining the two DNA-binding domains, AT-hook motif and HMG-1 boxes. It may be involved in the stability and/or transmission of the mitochondrial genome. To date, no structural homologues have been found in other organisms. However, mtHMG1 displays functional similarities with the
Saccharomyces cerevisiae
mitochondrial HMG-box protein Abf2.
Large-Scale Identification of Putative Exported Proteins in
Candida albicans
by Genetic Selection
Authors: Monteoliva L. , López Matas M. , Gil C. , Nombela C. , Pla J. 
Published: December 2002

ABSTRACT

In all living organisms, secreted proteins play essential roles in different processes. Of special interest is the construction of the fungal cell wall, since this structure is absent from mammalian cells. The identification of the proteins involved in its biogenesis is therefore a primary goal in antifungal research. To perform a systematic identification of such proteins in
Candida albicans
, we carried out a genetic screening in which in-frame fusions with an intracellular allele of invertase gene
SUC2
of
Saccharomyces cerevisiae
can be used to select and identify putatively exported proteins in the heterologous host
S
.
cerevisiae
. Eighty-three clones were selected, including 11 previously identified genes from
C
.
albicans
as well as 41
C
.
albicans
genes that encode proteins homologous to already described proteins from related organisms. They include enzymes involved in cell wall synthesis and protein secretion. We also found membrane receptors and transporters presumably related to the interaction of
C
.
albicans
with the environment as well as extracellular enzymes and proteins involved in different morphological transitions. In addition, 11
C
.
albicans
open reading frames (ORFs) identified in this screening encode proteins homologous to unknown or putative proteins, while 5 ORFs encode novel secreted proteins without known homologues in other organisms. This screening procedure therefore not only identifies a set of targets of interest in antifungal research but also provides new clues for understanding the topological locations of many proteins involved in processes relevant to the pathogenicity of this microorganism.
Isolation and Characterization of
YlBEM1
, a Gene Required for Cell Polarization and Differentiation in the Dimorphic Yeast
Yarrowia lipolytica
Authors: Hurtado Cleofe A. R. , Rachubinski Richard A. 
Published: December 2002

ABSTRACT

The ability to switch between a unicellular yeast form and different filamentous forms (fungal dimorphism) is an important attribute of most pathogenic fungi. Dimorphism involves a series of events that ultimately result in dramatic changes in the polarity of cell growth in response to environmental factors. We have isolated and characterized
YlBEM1
, a gene encoding a protein of 639 amino acids that is essential for the yeast-to-hypha transition in the yeast
Yarrowia lipolytica
and whose transcription is significantly increased during this event. Cells with deletions of
YlBEM1
are viable but show substantial alterations in morphology, disorganization of the actin cytoskeleton, delocalization of cortical actin and chitin deposition, multinucleation, and loss of mating ability, thus pointing to a major role for
YlBEM1
in the regulation of cell polarity and morphogenesis in this fungus. This role is further supported by the localization of YlBem1p, which, like cortical actin, appears to be particularly abundant at sites of growth of yeast, hyphal, and pseudohyphal cells. In addition, the potential involvement of YlBem1p in septum formation and/or cytokinesis is suggested by the concentration of a green fluorescent protein-tagged version of this protein at the mother-bud neck during the last stages of cell division. Interestingly, overexpression of
MHY1
,
YlRAC1
, or
YlSEC31
, three genes involved in filamentous growth of
Y. lipolytica
, induced hyphal growth of
bem1
null mutant cells.
Characterization of Inhibitor-Resistant Histone Deacetylase Activity in Plant-Pathogenic Fungi
Authors: Baidyaroy Dipnath , Brosch Gerald , Graessle Stefan , Trojer Patrick , Walton Jonathan D. 
Published: December 2002

ABSTRACT

HC-toxin, a cyclic peptide made by the filamentous fungus
Cochliobolus carbonum
, is an inhibitor of histone deacetylase (HDAC) from many organisms. It was shown earlier that the HDAC activity in crude extracts of
C. carbonum
is relatively insensitive to HC-toxin as well as to the chemically unrelated HDAC inhibitors trichostatin and D85, whereas the HDAC activity of
Aspergillus nidulans
is sensitive (G. Brosch et al., Biochemistry
40:
12855-12863, 2001). Here we report that HC-toxin-resistant HDAC activity was present in other, but not all, plant-pathogenic
Cochliobolus
species but not in any of the saprophytic species tested. The HDAC activities of the fungi
Alternaria brassicicola
and
Diheterospora chlamydosporia
, which also make HDAC inhibitors, were resistant. The HDAC activities of all
C. carbonum
isolates tested, except one non-toxin-producing isolate, were resistant. In a cross between a sensitive isolate and a resistant isolate, resistance genetically cosegregated with HC-toxin production. When fractionated by anion-exchange chromatography, extracts of resistant and sensitive isolates and species had two peaks of HDAC activity, one that was fully HC-toxin resistant and a second that was larger and sensitive. The first peak was consistently smaller in extracts of sensitive fungi than in resistant fungi, but the difference appeared to be insufficiently large to explain the differential sensitivities of the crude extracts. Differences in mRNA expression levels of the four known HDAC genes of
C. carbonum
did not account for the observed differences in HDAC activity profiles. When mixed together, resistant extracts protected extracts of sensitive
C. carbonum
but did not protect other sensitive
Cochlibolus
species or
Neurospora crassa
. Production of this extrinsic protection factor was dependent on
TOXE
, the transcription factor that regulates the HC-toxin biosynthetic genes. The results suggest that
C. carbonum
has multiple mechanisms of self-protection against HC-toxin.
Functional Diversity of Silencers in Budding Yeasts
Authors: Sjöstrand Jimmy O. O. , Kegel Andreas , Åström Stefan U. 
Published: December 2002

ABSTRACT

We studied the silencing of the cryptic mating-type loci
HML
α and
HMR
a in the budding yeast
Kluyveromyces lactis
. A 102-bp minimal silencer fragment was defined that was both necessary and sufficient for silencing of
HML
α. Mutagenesis of the silencer revealed three distinct regions (A, B, and C) that were important for silencing. Recombinant
K. lactis
ribosomal DNA enhancer binding protein 1 (Reb1p) could bind the silencer in vitro, and point mutations in the B box abolished both Reb1p binding and silencer function. Furthermore, strains carrying temperature-sensitive alleles of the
REB1
gene derepressed the transcription of the
HML
α
1
gene at the nonpermissive temperature. A functional silencer element from the
K. lactis
cryptic
HMR
a locus was also identified, which contained both Reb1p binding sites and A boxes, strongly suggesting a general role for these sequences in
K. lactis
silencing. Our data indicate that different proteins bind to
Kluyveromyces
silencers than to
Saccharomyces
silencers. We suggest that the evolution of silencers is rapid in budding yeasts and discuss the similarities and differences between silencers in
Saccharomyces
and
Kluyveromyces
.
Schizosaccharomyces pombe
Git7p, a Member of the
Saccharomyces cerevisiae
Sgt1p Family, Is Required for Glucose and Cyclic AMP Signaling, Cell Wall Integrity, and Septation
Authors: Schadick Kevin , Fourcade H. Matthew , Boumenot Peter , Seitz Jeffrey J. , Morrell Jennifer L. , Chang Louise , Gould Kathleen L. , Partridge Janet F. , Allshire Robin C. , Kitagawa Katsumi , Hieter Phil , Hoffman Charles S. 
Published: December 2002

ABSTRACT

The
Schizosaccharomyces pombe fbp1
gene, encoding fructose-1,6-bisphosphatase, is transcriptionally repressed by glucose. Mutations that confer constitutive
fbp1
transcription identify
git
(glucose-insensitive transcription) genes that encode components of a cyclic AMP (cAMP) signaling pathway required for adenylate cyclase activation. Four of these genes encode the three subunits of a heterotrimeric G protein (
gpa2
,
git5
, and
git11
) and a G protein-coupled receptor (
git3
). Three additional genes,
git1
,
git7
, and
git10
, act in parallel to or downstream from the G protein genes. Here, we describe the cloning and characterization of the
git7
gene. The Git7p protein is a member of the
Saccharomyces cerevisiae
Sgt1p protein family. In budding yeast, Sgt1p associates with Skp1p and plays an essential role in kinetochore assembly, while in
Arabidopsis
, a pair of SGT1 proteins have been found to be involved in plant disease resistance through an interaction with RAR1. Like
S
.
cerevisiae
Sgt1p, Git7p is essential, but this requirement appears to be due to roles in septation and cell wall integrity, which are unrelated to cAMP signaling, as
S
.
pombe
cells lacking either adenylate cyclase or protein kinase A are viable. In addition,
git7
mutants are sensitive to the microtubule-destabilizing drug benomyl, although they do not display a chromosome stability defect. Two alleles of
git7
that are functional for cell growth and septation but defective for glucose-triggered cAMP signaling encode proteins that are altered in the highly conserved carboxy terminus. The
S
.
cerevisiae
and human
SGT1
genes both suppress
git7-93
but not
git7-235
for glucose repression of
fbp1
transcription and benomyl sensitivity. This allele-specific suppression indicates that the Git7p/Sgt1p proteins may act as multimers, such that Git7-93p but not Git7-235p can deliver the orthologous proteins to species-specific targets. Our studies suggest that members of the Git7p/Sgt1p protein family may play a conserved role in the regulation of adenylate cyclase activation in
S
.
pombe
,
S
.
cerevisiae
, and humans.
Sgt1p Contributes to Cyclic AMP Pathway Activity and Physically Interacts with the Adenylyl Cyclase Cyr1p/Cdc35p in Budding Yeast
Authors: Dubacq Caroline , Guerois Raphaël , Courbeyrette Régis , Kitagawa Katsumi , Mann Carl 
Published: December 2002

ABSTRACT

Sgt1p is a highly conserved eucaryotic protein that is required for both SCF (Skp1p/Cdc53p-Cullin-F-box)-mediated ubiquitination and kinetochore function in yeast. We show here that Sgt1p is also involved in the cyclic AMP (cAMP) pathway in
Saccharomyces cerevisiae
.
SGT1
is an allele-specific suppressor of
cdc35-1
, a thermosensitive mutation in the leucine-rich repeat domain of the adenylyl cyclase Cyr1p/Cdc35p. We demonstrate that Sgt1p and Cyr1p/Cdc35p physically interact and that the activity of the cAMP pathway is affected in an
sgt1
conditional mutant. Sequence analysis suggests that Sgt1p has features of a cochaperone. Thus, Sgt1p is a novel activator of adenylyl cyclase in
S
.
cerevisiae
and may function in the assembly or the conformational activation of specific multiprotein complexes.
New Class of Cargo Protein inTetrahymena thermophilaDense Core Secretory Granules
Authors: Haddad Alex , Bowman Grant R. , Turkewitz Aaron P. 
Published: December 2002

ABSTRACTRegulated exocytosis of dense core secretory granules releases biologically active proteins in a stimulus-dependent fashion. The packaging of the cargo within newly forming granules involves a transition: soluble polypeptides condense to form water-insoluble aggregates that constitute the granule cores. Following exocytosis, the cores generally disassemble to diffuse in the cell environment. The ciliatesTetrahymena thermophilaandParamecium tetraureliahave been advanced as genetically manipulatable systems for studying exocytosis via dense core granules. However, all of the known granule proteins in these organisms condense to form the architectural units of lattices that are insoluble both before and after exocytosis. Using an approach designed to detect new granule proteins, we have now identified Igr1p (induced during granule regeneration). By structural criteria, it is unrelated to the previously characterized lattice-forming proteins. It is distinct in that it is capable of dissociating from the insoluble lattice following secretion and therefore represents the first diffusible protein identified in ciliate granules.
Trichoderma atroviride
G-Protein α-Subunit Gene
tga1
Is Involved in Mycoparasitic Coiling and Conidiation
Authors: Rocha-Ramírez Víctor , Omero Carmi , Chet Ilan , Horwitz Benjamin A. , Herrera-Estrella Alfredo 
Published: December 2002

ABSTRACT

The soil fungus
Trichoderma atroviride
, a mycoparasite, responds to a number of external stimuli. In the presence of a fungal host,
T
.
atroviride
produces hydrolytic enzymes and coils around the host hyphae. In response to light or nutrient depletion, asexual sporulation is induced. In a biomimetic assay, different lectins induce coiling around nylon fibers; coiling in the absence of lectins can be induced by applying cyclic AMP (cAMP) or the heterotrimeric G-protein activator mastoparan. We isolated a
T
.
atroviride
G-protein α-subunit (Gα) gene (
tga1
) belonging to the fungal subfamily with the highest similarity to the Gα
i
class. Generated transgenic lines that overexpress Gα show very delayed sporulation and coil at a higher frequency. Furthermore, transgenic lines that express an activated mutant protein with no GTPase activity do not sporulate and coil at a higher frequency. Lines that express an antisense version of the gene are hypersporulating and coil at a much lower frequency in the biomimetic assay. The loss of Tga1 in these mutants correlates with the loss of GTPase activity stimulated by the peptide toxin Mas-7. The application of Mas-7 to growing mycelial colonies raises intracellular cAMP levels, suggesting that Tga1 can activate adenylyl cyclase. In contrast, cAMP levels and cAMP-dependent protein kinase activity drop when diffusible host signals are encountered and the mycoparasitism-related genes
ech42
and
prb1
are highly expressed. Mycoparasitic signaling is unlikely to be a linear pathway from host signals to increased cAMP levels. Our results demonstrate that the product of the
tga1
gene is involved in both coiling and conidiation.
Interaction with Btn2p Is Required for Localization of Rsg1p: Btn2p-Mediated Changes in Arginine Uptake in
Saccharomyces cerevisiae
Authors: Chattopadhyay Subrata , Pearce David A. 
Published: December 2002

ABSTRACT

Btn2p, a novel coiled-coil protein, is up-regulated in
btn1
Δ yeast strains, and this up-regulation is thought to contribute to maintaining a stable vacuolar pH in
btn1
Δ strains (D. A. Pearce, T. Ferea, S. A. Nosel, B. Das, and F. Sherman, Nat. Genet.
22:
55-58, 1999). We now report that Btn2p interacts biochemically and functionally with Rsg1p, a down-regulator of the Can1p arginine and lysine permease. Rsg1p localizes to a distinct structure toward the cell periphery, and strains lacking Btn2p (
btn2
Δ strains) fail to correctly localize Rsg1p.
btn2
Δ strains, like
rsg1
Δ strains, are sensitive for growth in the presence of the arginine analog canavanine. Furthermore,
btn2
Δ strains, like
rsg1
Δ strains, demonstrate an elevated rate of uptake of [
14
C]arginine, which leads to increased intracellular levels of arginine. Overexpression of
BTN2
results in a decreased rate of arginine uptake. Collectively, these results indicate that altered levels of Btn2p can modulate arginine uptake through localization of the Can1p-arginine permease regulatory protein, Rsg1p. Our original identification of Btn2p was that it is up-regulated in the
btn1
Δ strain which serves as a model for the lysosomal storage disorder Batten disease. Btn1p is a vacuolar/lysosomal membrane protein, and
btn1
Δ suppresses both the canavanine sensitivity and the elevated rate of uptake of arginine displayed by
btn2
Δ
rsg1
Δ strains. We conclude that Btn2p interacts with Rsg1p and modulates arginine uptake. Up-regulation of
BTN2
expression in
btn1
Δ strains may facilitate either a direct or indirect effect on intracellular arginine levels.
The Fission Yeast Ubiquitin-Conjugating Enzymes UbcP3, Ubc15, and Rhp6 Affect Transcriptional Silencing of the Mating-Type Region
Authors: Sig Nielsen Inga , Nielsen Olaf , Murray Johanne M. , Thon Geneviève 
Published: December 2002

ABSTRACT

Genes transcribed by RNA polymerase II are silenced when introduced near the
mat2
or
mat3
mating-type loci of the fission yeast
Schizosaccharomyces pombe
. Silencing is mediated by a number of gene products and
cis
-acting elements. We report here the finding of novel
trans
-acting factors identified in a screen for high-copy-number disruptors of silencing. Expression of cDNAs encoding the putative E2 ubiquitin-conjugating enzymes UbcP3, Ubc15 (ubiquitin-conjugating enzyme), or Rhp6 (Rad homolog
pombe
) from the strong
nmt1
promoter derepressed the silent mating-type loci
mat2
and
mat3
and reporter genes inserted nearby. Deletion of
rhp6
slightly derepressed an
ade6
reporter gene placed in the mating-type region, whereas disruption of
ubcP3
or
ubc15
had no obvious effect on silencing. Rhp18 is the
S. pombe
homolog of
Saccharomyces cerevisiae
Rad18p, a DNA-binding protein that physically interacts with Rad6p. Rhp18 was not required for the derepression observed when UbcP3, Ubc15, or Rhp6 was overproduced. Overexpressing Rhp6 active-site mutants showed that the ubiquitin-conjugating activity of Rhp6 is essential for disruption of silencing. However, high dosage of UbcP3, Ubc15, or Rhp6 was not suppressed by a mutation in the 26S proteasome, suggesting that loss of silencing is not due to an increased degradation of silencing factors but rather to the posttranslational modification of proteins by ubiquitination. We discuss the implications of these results for the possible modes of action of UbcP3, Ubc15, and Rhp6.
Colletotrichum trifolii
TB3 Kinase, a COT1 Homolog, Is Light Inducible and Becomes Localized in the Nucleus during Hyphal Elongation
Authors: Chen Changbin , Dickman Martin B. 
Published: December 2002

ABSTRACT

Colletotrichum trifolii
is a fungal pathogen responsible for anthracnose disease of alfalfa. Previously, a serine/threonine protein kinase gene from this fungus (TB3), which is a functional homolog of the
Neurospora crassa
COT1 kinase, has been isolated in our laboratory and appears to be associated with hyphal elongation and branching. In this report we show that light treatment rapidly induces TB3 expression and hyphal branching frequency. Western analysis showed TB3 localization in both the cytoplasm and nucleus, but not in membranes. Moreover, indirect immunofluorescence indicated that TB3 levels were most abundant in the nucleus. To further evaluate the subcellular distribution of TB3, a TB3::GFP fusion construct was inserted into
C. trifolii
. Results indicated that the cellular location of TB3 changed during fungal growth and development. Consistent with previous observations, TB3 was localized in both the cytoplasm and the nucleus but was preferentially localized in the nucleus during extended hyphal growth. The amino terminus of TB3 contains two relatively long polyglutamine repeats. Yeast-based assays showed that these polyglutamine tracts can activate transcription. These results suggest that TB3 may be positioned in a signaling cascade regulating proper hyphal growth and development by functioning as a transcription factor.