bluuebunny/crossref_metadata_2025_split huggingface dataset:
Axin, an inhibitor of the Wnt signalling pathway, interacts with β‐catenin, GSK‐3β and APC and reduces the β‐catenin level
Authors: Nakamura Tsutomu , Hamada Fumihiko , Ishidate Takao , Anai Ken‐ichi , Kawahara Kohichi , Toyoshima Kumao , Akiyama Tetsu 
Published: March 2003

Background:The Wnt/Wingless signalling pathway plays an important role in both embryonic development and tumorigenesis. β‐Catenin and Axin are positive and negative effectors of the Wnt signalling pathway, respectively.Results:We found that Axin interacts with β‐catenin and glycogen synthase kinase‐3β (GSK‐3β). Furthermore, the regulation of the G‐protein signalling (RGS) domain of Axin is associated with the colorectal tumour suppressor adenomatous polyposis coli (APC). Overexpression of Axin in the human colorectal cancer cell line SW480 induced a drastic reduction in the level of β‐catenin. Interaction with β‐catenin and GSK‐3β was required for the Axin‐mediated β‐catenin reduction.Conclusion:Axin interacts with β‐catenin, GSK‐3β and APC, and negatively regulates the Wnt signalling pathway, presumably by regulating the level of β‐catenin.
Post‐transcriptional control of the level of mRNA by hepatitis B virus X gene in the transient expression system using human hepatic cells
Authors: Shimazu Tsutomu , Takada Shinako , Ueno Yoshio , Hayashi Yasuyuki , Koike Katsuro 
Published: March 2003

BackgroundHepatitis B virus (HBV) infection is closely related to the development of not only acute or chronic hepatitis, but also hepatocellular carcinoma. Among the HBV genes, the X gene has been implicated in the carcinogenicity of this virus as a major causative factor by its ability to activate viral and cellular genes in trans via protein–protein interaction with cellular factors without binding to DNA.ResultsTo explore the possibility of other functions of the X gene, we examined the effect of X protein on the transient expression system of simian virus 40 (SV40) large T‐antigen or chloramphenicol acetyltransferase (CAT) mRNA using SV40 promoter or EF‐1α (human elongation factor 1α) promoter, by co‐transfecting an X gene expression plasmid to human hepatic cell lines, HepG2 and Huh7. In contrast to the SV40 promoter‐mediated expression, the level of both T‐antigen and CAT mRNAs expressed from the EF‐1α promoter was strikingly decreased by X protein in both hepatic cells. The nuclear run‐on assay and the mRNA decay experiment using actinomycin D, indicated that the effect of X protein on the lowering of the level of chimeric mRNA was due to the degradation of mRNA, but not repression of transcriptional initiation. Moreover, this effect was dependent on the 22 bp sequence in the 5′ untranslated region of mRNA derived from the EF‐1α promoter.ConclusionThe present data suggest a new function of the X gene to post‐transcriptionally control the stability of mRNA through the 5′ untranslated region derived from the EF‐1α promoter in human hepatic cells.
Isolation and characterization of cortactin isoforms and a novel cortactin‐binding protein, CBP90
Authors: Ohoka Yoshiharu , Takai Yoshimi 
Published: March 2003

BackgroundCortactin is a major phosphotyrosyl protein in pp60v–src‐transformed chicken embryo cells. Cortactin binds to actin filament (F‐actin) through a unique region which consists of six tandem 37 amino acid repeats, named cortactin repeats. Furthermore cortactin has one src homology 3 (SH3) domain.ResultsIn this study we have isolated two new isoforms of cortactin from the rat brain using a polymerase chain reaction (PCR) method, and have named the original cortactin as cortactin‐A and the newly isolated forms as cortactin‐B and ‐C. Cortactin‐A, ‐B and ‐C had six, five, and four cortactin repeats, respectively. All the isoforms were able to bind to F‐actin, but only cortactin‐A demonstrated an F‐actin‐crosslinking activity. In addition, cortactin‐A was able to bind along the side of F‐actin. Next, using a blot overlay assay with glutathione S‐transferase (GST)‐cortactin‐A, we identified a cortactin‐A‐binding protein with an Mr of ≈90 kDa in rat brain and named it CBP90 (cortactin‐binding protein with an Mr of ≈90 KDa). CBP90 was purified from rat brain and its cDNA was cloned from a rat brain cDNA library. The deduced amino acid sequence of CBP90 had no significant similarity to any other protein, but it had a proline‐rich domain at the C‐terminal region. CBP90 was able to bind to all the cortactin isoforms. A deletion mutant analysis of cortactin‐A and CBP90 revealed that the SH3 domain of cortactin‐A was able to bind to the proline‐rich region of CBP90. A Western blot analysis with an anti‐CBP90 antibody indicated that, among the rat tissues examined, CBP90 was exclusively expressed in brain. Furthermore, its subcellular distribution and developmental expression patterns were similar to those of cortactin.ConclusionThese results suggest that cortactin interacts with CBP90 and plays a role in regulation of the actin cytoskeleton in brain.
Abnormalities of developmental cell death in Dad1‐deficient mice
Authors: Nishii Kiyomasa , Tsuzuki Teruhisa , Kumai Madoka , Takeda Naoki , Koga Hideya , Aizawa Shinichi , Nishimoto Takeharu , Shibata Yosaburo 
Published: March 2003

BackgroundDad1, the defender against apoptotic cell death, comprises the oligosaccharyltransferase complex and is well conserved among eukaryotes. In hamster BHK21‐derived tsBN7 cells, loss of Dad1 causes apoptosis which cannot be prevented by Bcl‐2.ResultsTo determine the role of Dad1 function in vivo, we prepared by gene targeting, mice harbouring a disrupted Dad1 gene. Homozygous mutants died shortly after they were implanted with the characteristic features of apoptosis. In an in vitro blastocyst culture system, Dad1‐null cells displayed abnormalities which were comparable to those obtained in vivo. However, oligosaccharyltransferase activity was apparently retained even after the Dad1‐null cells were destined to die. Some live‐born heterozygous mutants displayed soft‐tissue syndactyly. Mild thymic hypoplasia was also indicated in heterozygotes.ConclusionThese results suggest the involvement of the Dad1 gene in the acquisition of a common syndactyly phenotype, as well as in the control of programmed cell death during development.
Triggering of neuronal cell death by accumulation of activated SEK1 on nuclear polyglutamine aggregations in PML bodies
Authors: Yasuda Shingo , Inoue Kiyoshi , Hirabayashi Miho , Higashiyama Hiroyuki , Yamamoto Yukio , Fuyuhiro Haruko , Komure Osamu , Tanaka Fumiaki , Sobue Gen , Tsuchiya Kuniaki , Hamada Koji , Sasaki Hidenao , Takeda Kohsuke , Ichijo Hidenori , Kakizuka Akira 
Published: March 2003

BackgroundA novel class of inherited human neurodegenerations is now known to be caused by expanded CAG repeats encoding polyglutamines. Polyglutamine‐containing protein fragments have been shown to accumulate as aggregates in the nucleus and in the cytoplasm, and to induce cell death when expressed in cultured cells, leading to the proposal that polyglutamine aggregation is an important step in the pathogenesis. Supporting this, nuclear inclusions containing expanded polyglutamines have been identified in neurones from the brains of patients and in neurones from transgenic mouse models of this class of neural disorders.ResultsWe analysed the consequences of polyglutamine expression in PC12 neuronal cells. Activated SEK1 accumulated with nuclear but not cytoplasmic polyglutamine aggregations, which consequently triggers cell death. Cell death induced by polyglutamine expression was inhibited by a dominant‐negative SEK1 (DN‐SEK1), but not by DN‐SEK1 tagged with a nuclear export signal. Steady state SEK1 expression itself was enhanced two to three‐fold. Nuclearly aggregated polyglutamines, which were identified in PML bodies, co‐localized with not only activated SEK1 but also activated c‐Jun. We also observed that nuclear inclusion‐positive neurones from brains with Huntington's disease expressed SEK1.ConclusionsThis study provides molecular links between the neurodegeneration observed in polyglutamine diseases, cell death signalling kinase cascades and nuclear subdomains related to cell death. We propose that the nuclear PML bodies containing polyglutamine aggregates activate the SEK1‐JNK kinase cascade, resulting in the transduction of a death signal.
Central role for Cdc45 in establishing an initiation complex of DNA replication in Xenopus egg extracts
Authors: Mimura Satoru , Masuda Taro , Matsui Tomoko , Takisawa Haruhiko 
Published: March 2003

BackgroundIn eukaryotes, chromosomal DNA is licensed to be replicated through the sequential loading of the origin recognition complex, Cdc6 and mini‐chromosome maintenance protein complex (MCM) onto chromatin. However, how the replication machinery is assembled onto the licensed chromatin during initiation of replication is poorly understood.ResultsUsing Xenopus egg extracts, we have investigated the role of Cdc45 in the loading of various replication proteins onto chromatin at the onset of S phase, and found that Cdc45, which required MCM for its loading, was essential for the sequential loading of replication protein A (RPA), DNA polymerase α and proliferating cell nuclear antigen (PCNA) onto chromatin. The assembly of DNA polymerase ɛ onto chromatin required Cdc45 but did not require DNA polymerase α. Analysis of nuclease‐digested chromatin fractions shows that Cdc45 formed a stable complex with either MCM or DNA polymerase α on chromatin.ConclusionsThese results demonstrate a central role for Cdc45 in activation of the licensed chromatin to form replication complexes at the onset of S phase, and suggest that Cdc45 has a dual role in the initiation of DNA replication: the unwinding of DNA and the recruiting of DNA polymerases onto DNA.
BIP, a BRAM‐interacting protein involved in TGF‐β signalling, regulates body length in Caenorhabditis elegans
Authors: Sugawara Katsura , Morita Kiyokazu , Ueno Naoto , Shibuya Hiroshi 
Published: March 2003

Background The TGF‐β superfamily has diverse biological activities and is involved in the early development of animals. We previously identified a novel family member, BMP receptor associated molecule (BRAM), which binds to the intracellular domain of BMP type IA receptor and is involved in the BMP signalling pathway.Results To identify novel molecules involved in TGF‐β signalling pathways, we performed yeast two‐hybrid screening using BRAM as bait. From a Xenopus cDNA library, we cloned a cDNA encoding 693 amino acids and containing the motif for an oxysterol binding protein (OSBP), which we designated BRAM interacting protein (BIP). We then isolated a BIP homologue from the Caenorhabditis elegans that encodes 733 amino acids and also contains the OSBP‐like motif. Immunoprecipitation and Western blotting studies revealed that C. elegans BIP could interact with the C. elegans BRAM homologues BRA‐1 and BRA‐2. C. elegans BIP was expressed in pharyngeal muscle, hypodermis and several neuronal cells, an expression pattern overlaps with those of BRA‐1 and BRA‐2. Finally, we found that inhibition of BIP expression in C. elegans by double stranded RNA interference produces a Sma phenotype.Conclusions BIP was isolated using the yeast two‐hybrid systems. BIP may function in the TGF‐β pathway and regulate body length in C. elegans.
Functional interactions of an archaeal sliding clamp with mammalian clamp loader and DNA polymerase δ
Authors: Ishino Yoshizumi , Tsurimoto Toshiki , Ishino Sonoko , Cann Isaac K. O. 
Published: March 2003

BackgroundBy the total genome sequencing of several archaeal organisms, it has been confirmed that many archaeal proteins related to genetic information systems, including DNA replication, transcription and translation, have similar sequences to those of eukaryotes. In eukaryotic DNA replication, proliferating cell nuclear antigen (PCNA) works in clamping DNA polymerases on the DNA template and accomplishes a processive DNA synthesis. Archaea encode PCNA homologues in their genomes andPyrococcus furiosusPCNA (PfuPCNA) stimulates the DNA synthesizing activities of the DNA polymerases, Pol I and Pol II, in this organism.ResultsWe have demonstrated thatPfuPCNA interacts functionally with calf thymus DNA polymerase δ (Pol δ) and stimulates its activity. Moreover, human replication factor C (RFC) enhances thePfuPCNA‐dependent DNA synthesis activity of Pol δ, indicating that human RFC works as the clamp loader forPfuPCNA. These results showed that the three‐dimensional structures of archaral PCNA and RFC are actually similar enough to their eukaryotic counterparts to allow a molecular substitution between the two biological domains, albeit at a lower efficiency.ConclusionsWe found that the archaeal molecule interacts functionally with the eukaryotic members in the DNA replication process. This finding supports the idea that studies on the DNA replication mechanism of archaeal organisms will provide many important clues for understanding of the intricate molecular recognition that is inherent to the DNA replication machinery in Eukarya.
Two domains of Nrf2 cooperatively bind CBP, a CREB binding protein, and synergistically activate transcription
Authors: Katoh Yasutake , Itoh Ken , Yoshida Eisaku , Miyagishi Makoto , Fukamizu Akiyoshi , Yamamoto Masayuki 
Published: March 2003

Background Nrf2 belongs to the Cap‐N‐Collar (CNC) transcription factor family and is essential for the antioxidant responsive element (ARE)‐mediated expression of a group of detoxifying and antioxidant genes. The forced expression of Nrf2 in mammalian cells activates the expression of target genes through the ARE, with Nrf2 showing the highest transactivation activity among the CNC family of transcription factors. To elucidate the molecular mechanisms generating this potent transactivation activity, we examined the functions of the domains within Nrf2.Result We found that Nrf2 contains two transcription activation domains, Neh4 and Neh5, which act synergistically to attain maximum a activation of reporter gene expression. Neh4 and Neh5 both individually and cooperatively bind to CBP (CREB (cAMP Responsive Element Binding protein) Binding Protein). In fact, the specific inhibitor of CBP, adenovirus E1A protein, significantly reduced Nrf2 activity. Importantly, the CBP‐binding activity of Nrf2 deletion mutants positively correlated with their transactivation activity. Neh5 contains a motif which is commonly conserved among the CNC factors, whereas Neh4 contains the novel CBP‐interacting motif recently identified in p53 and E2F.Conclusions Our results indicate that Nrf2 exploits the cooperative binding of two independent transactivation domains to CBP in the acquisition of a potent transactivation activity.
Disruption of MSSP, c‐myc single‐strand binding protein, leads to embryonic lethality in some homozygous mice
Authors: Fujimoto Mitsuaki , Matsumoto Ken‐ichi , Iguchi‐Ariga Sanae M. M. , Ariga Hiroyoshi 
Published: March 2003

Background MSSP, c‐myc single‐strand binding protein, works as a factor for DNA replication, transcription, apoptosis induction, and myc/ras cooperative transformation. The cDNAs encoding four of the family proteins, MSSP‐1, MSSP‐2, Scr2 and Scr3, were cloned. These proteins possess two copies of putative RNA binding domains, RNP‐A and RNP‐B, and these RNA binding domains have been suggested to be indispensable to the functions of MSSP.Results To elucidate its role in vivo, we generated Mssp knockout mice by homologous recombination in embryonic stem cells. Although intercrossing of Mssp+/– mice gave rise to mice homozygous to the mutant Mssp allele (Mssp−/–) and the Mssp−/– mice, once born, did not display an overt phenotype, the ratio of littermates born among Mssp+/+, Mssp+/– and Mssp−/– mice was 1 : 1.6 : 0.5, which is not a typical Mendelian ratio. When E2.5 embryos from the pregnant mice were cultured in vitro for 5 days, the inner cell mass and trophoblast giant cells in wild‐type (Mssp+/+) E2.5 embryos developed normally. However, Mssp−/– E2.5 embryos displayed significant defects in growth and development. Since Mssp was expressed in uterine gland‐transported glycogen, we evaluated the hormonal state of wild‐type and Mssp−/– mice. The progesterone concentration of Mssp−/– mice was decrease to 6.5% of that of wild‐type mice at E2.5.Conclusions These results suggest that the deletion of the mssp gene results in both the growth defect in the embryo and the hormonal defect in adult female mouse. The embryonic defect and a decreased concentration of progesterone in female mice reflect a development defect of the pre‐implantation embryo in Mssp−/– mice, thereby leading to embryonic lethality.
Vacuolar membrane dynamics revealed by GFP‐AtVam3 fusion protein
Authors: Uemura Tomohiro , Yoshimura Shige H. , Takeyasu Kunio , Sato Masa H. 
Published: March 2003

AbstractBackground: The plant vacuole is a multifunctional organelle that has various physiological functions. The vacuole dynamically changes its function and shape, dependent on developmental and physiological conditions. Our current understanding of the dynamic processes of vacuolar morphogenesis has suffered from the lack of a marker for observing these processes in living cells.Results: We have developed transgenic Arabidopsis thaliana expressing a vacuolar syntaxin‐related molecule (AtVam3/SYP22) fused with green fluorescent protein (GFP). Observations using confocal laser scanning microscopy demonstrated that the plant vacuole contained a dynamic membrane system that underwent a complex architectural remodelling. Three‐dimensional reconstitution and time‐lapse analysis of GFP‐fluorescence images revealed that cylindrical and sheet‐like structures were present in the vacuolar lumen and were moving dynamically. The movement, but not the structure itself, was abolished by cytochalasin D, an inhibitor of actin polymerization. This moving structure, which sometimes penetrated through the vacuolar lumen, possessed a dynamic membrane architecture similar to the previously recognized ‘transvacuolar strand.’Conclusion: We propose two possible models for the formation of the vacuolar lumenal structure. Membrane structures including protruding tubules and reticular networks have recently been recognized in many other organelles, and may be actively involved in intra‐ and/or inter‐organelle signalling.
A possible linkage between AMP‐activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) signalling pathway
Authors: Kimura Naoki , Tokunaga Chiharu , Dalal Sushila , Richardson Christine , Yoshino Ken‐ichi , Hara Kenta , Kemp Bruce E. , Witters Lee A. , Mimura Osamu , Yonezawa Kazuyoshi 
Published: March 2003

AbstractBackground: The mammalian target of rapamycin (mTOR) regulates multiple cellular functions including translation in response to nutrients, especially amino acids. AMP‐activated protein kinase (AMPK) modulates metabolism in response to energy demand by responding to changes in AMP.Results: The treatment of SV40‐immortalized human corneal epithelial cells (HCE‐T cells) with 5‐aminoimidazole‐4‐carboxamide ribonucleoside (AICAR), widely used as an AMPK activator, inhibits p70 S6k activities. Altered glucose availability, which regulates AMPK activity, also modulates the activity of p70 S6k. AICAR treatment also inhibits phosphorylation of Thr‐412 in the p70 S6 kinase (p70 S6k), which is indispensable for the activity. Furthermore, over‐expression of mutant AMPK subunits by stable expression in rabbit pulmonary fibroblast cell lines (PS120 cells) also modulates p70 S6k activity. The insensitivity of the rapamycin‐resistant p70 S6k variant to AICAR treatment suggests that the inhibition of p70 S6k is mediated through a common effector, supporting a model whereby mTOR and its downstream effector are controlled by AMPK.Conclusion: These results indicate that the AMPK and mTOR signalling pathways are possibly linked. In addition to the mTOR signal acting as a priming switch that modulates p70 S6k activation, AMPK appears to provide an overriding switch linking p70 S6k regulation to cellular energy metabolism.
Seismic imaging of the shallow subsurface: shear‐wave case histories
Authors: Dasios  , McCann  , Astin  , McCann  , Fenning  
Published: March 2003

Obtaining high‐resolution images of the geology and hydrogeology of the subsurface in the depth range from ground level to 50 m is one of the major challenges of modern geophysics. The methods which are commonly used (such as compressional‐wave surveys and ground‐penetrating radar) often suffer from adverse effects caused by the near‐surface conditions, changes in water saturation and various sources of noise. This paper demonstrates some of the advantages offered by the use of shear‐wave seismology and by the combination of shear‐ and compressional‐wave seismic methods in shallow subsurface investigations.Multicomponent shallow seismic tests were carried out at four different sites to examine the effectiveness of different acquisition geometries under a variety of near‐surface geological conditions. Near‐surface conditions encountered at the sites included thick clays, clay/sand sequences overlying Chalk, mudstone overlying granodiorite bedrock and landfill material.Under all conditions, shear‐wave data acquisition was found to have advantages over compressional‐wave acquisition for the investigation of the shallow subsurface. Shear head waves, being unaffected by water saturation, achieved penetration to greater depths at a site in Crewkerne, Dorset where compressional head‐wave penetration was limited to the near‐surface layers. Better vertical resolution was achieved at shallow depths using shear‐wave reflection energy at a landfill site. Shear‐wave reflections from shallow interfaces were in some cases less affected by noise compared with the equivalent compressional‐wave reflections. Combinations of shear‐ and compressional‐wave data recording allowed the measurement of a Poisson's ratio log and gave indications of seismic anisotropy at two sites where dipping clay layers were present.
Improved amplitude preservation for prestack depth migration by inverse scattering theory
Authors: Shin Changsoo , Jang Seonghyung , Min Dong‐Joo 
Published: March 2003

A prestack reverse time‐migration image is not properly scaled with increasing depth. The main reason for the image being unscaled is the geometric spreading of the wavefield arising during the back‐propagation of the measured data and the generation of the forward‐modelled wavefields. This unscaled image can be enhanced by multiplying the inverse of the approximate Hessian appearing in the Gauss–Newton optimization technique. However, since the approximate Hessian is usually too expensive to compute for the general geological model, it can be used only for the simple background velocity model.We show that the pseudo‐Hessian matrix can be used as a substitute for the approximate Hessian to enhance the faint images appearing at a later time in the 2D prestack reverse time‐migration sections. We can construct the pseudo‐Hessian matrix using the forward‐modelled wavefields (which are used as virtual sources in the reverse time migration), by exploiting the uncorrelated structure of the forward‐modelled wavefields and the impulse response function for the estimated diagonal of the approximate Hessian. Although it is also impossible to calculate directly the inverse of the pseudo‐Hessian, when using the reciprocal of the pseudo‐Hessian we can easily obtain the inverse of the pseudo‐Hessian. As examples supporting our assertion, we present the results obtained by applying our method to 2D synthetic and real data collected on the Korean continental shelf.