Biomedical subjects

Ryuji Kobayashi

Publications and source records attributed to Ryuji Kobayashi.

41 records · Page 3Linked to original sources

PubMed2002

ISWI remodeling complexes in Xenopus egg extracts: identification as major chromosomal components that are regulated by INCENP-aurora B.

We previously characterized major components of mitotic chromosomes assembled in Xenopus laevis egg extracts and collectively referred to them as Xenopus chromosome-associated polypeptides (XCAPs). They included five subunits of the condensin complex essential for chromosome condensation. In an effort to identify novel proteins involved in this process, we have isolated XCAP-F and found it to be the Xenopus ortholog of ISWI, a chromatin remodeling ATPase. ISWI exists in two major complexes in Xenopus egg extracts. The first complex contains ACF1 and two low-molecular-weight subunits, most likely corresponding to Xenopus CHRAC. The second complex is a novel one that contains the Xenopus ortholog of the human Williams syndrome transcription factor (WSTF). In the absence of the ISWI complexes, the deposition of histones onto DNA is apparently normal, but the spacing of nucleosomes is greatly disturbed. Despite the poor spacing of nucleosomes, ISWI depletion has little effect on DNA replication, chromosome condensation or sister chromatid cohesion in the cell-free extracts. The association of ISWI with chromatin is cell cycle regulated and is under the control of the INCENP-aurora B kinase complex that phosphorylates histone H3 during mitosis. Apparently contradictory to the generally accepted model, we find that neither chromosome condensation nor chromosomal targeting of condensin is compromised when H3 phosphorylation is drastically reduced by depletion of INCENP-aurora B.

Adenosine Triphosphatases↗

PubMed2002

Identification, cDNA cloning, and targeted deletion of p70, a novel, ubiquitously expressed SH3 domain-containing protein.

In a screen for proteins that interact with Jak2, we identified a previously uncharacterized 70-kDa protein and cloned the corresponding cDNA. The predicated sequence indicates that p70 contains an SH3 domain and a C-terminal domain with similarities to the catalytic motif of phosphoglycerate mutase. p70 transcripts were found in all tissues examined. Similarly, when an antibody raised against a C-terminal peptide to analyze p70 protein expression was used, all murine tissues examined were found to express p70. To investigate the in vivo role of p70, we generated a p70-deficient mouse strain. Mice lacking p70 are viable, develop normally, and do not display any obvious abnormalities. No differences were detected in various hematological parameters, including bone marrow colony-forming ability, in response to cytokines that utilize Jak2. In addition, no impairment in B- and T-cell development and proliferative ability was detected.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Characterization of human RNA polymerase III identifies orthologues for Saccharomyces cerevisiae RNA polymerase III subunits.

Unlike Saccharomyces cerevisiae RNA polymerase III, human RNA polymerase III has not been entirely characterized. Orthologues of the yeast RNA polymerase III subunits C128 and C37 remain unidentified, and for many of the other subunits, the available information is limited to database sequences with various degrees of similarity to the yeast subunits. We have purified an RNA polymerase III complex and identified its components. We found that two RNA polymerase III subunits, referred to as RPC8 and RPC9, displayed sequence similarity to the RNA polymerase II RPB7 and RPB4 subunits, respectively. RPC8 and RPC9 associated with each other, paralleling the association of the RNA polymerase II subunits, and were thus paralogues of RPB7 and RPB4. Furthermore, the complex contained a prominent 80-kDa polypeptide, which we called RPC5 and which corresponded to the human orthologue of the yeast C37 subunit despite limited sequence similarity. RPC5 associated with RPC53, the human orthologue of S. cerevisiae C53, paralleling the association of the S. cerevisiae C37 and C53 subunits, and was required for transcription from the type 2 VAI and type 3 human U6 promoters. Our results provide a characterization of human RNA polymerase III and show that the RPC5 subunit is essential for transcription.

Amino Acid Sequence↗

PubMedDate not supplied

Function of the upper extremity and ability to perform housework following reconstructive surgery of the shoulder joint using a free vascularized fibula bone graft: a case report.

The cases of two female patients who underwent reconstructive surgery using free vascularized fibular bone grafting of the proximal humerus are reported. Both patients were evaluated 1 year postoperatively for active range of motion; an Enneking evaluation and activities-of-daily-living (housework) assessment were also done. Patient 1 regained flexion and abduction to 110 degrees, and patient 2 regained flexion and abduction to 90 degrees. On the Enneking test, the patients achieved scores of 23 and 25 points, respectively. On the activities-of-daily-living housework assessment, patient 1 performed at 91.0% and patient 2 at 60.6%. In both cases, neither active range of motion nor the Enneking scores accurately reflected the functional abilities of the reconstructed limbs. It is important that upper extremity therapists evaluate and consider functional abilities in activities of daily living, such as housework, in the early phases of rehabilitation.

Activities of Daily Living↗

PubMedDate not supplied

Direct tandem mass spectrometry reveals limitations in protein profiling experiments for plasma biomarker discovery.

The low molecular weight plasma proteome and its biological relevance are not well defined; therefore, experiments were conducted to directly sequence and identify peptides observed in plasma and serum protein profiles. Protein fractionation, matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) profiling, and liquid-chromatography coupled to MALDI tandem mass spectrometry (MS/MS) sequencing were used to analyze the low molecular weight proteome of heparinized plasma. Four fractionation techniques using functionally derivatized 96-well plates were used to extract peptides from plasma. Tandem TOF was successful for identifying peptides up to m/z 5500 with no prior knowledge of the sequence and was also used to verify the sequence assignments for larger ion signals. The peptides (n>250) sequenced in these profiles came from a surprisingly small number of proteins (n approximately 20), which were all common to plasma, including fibrinogen, complement components, antiproteases, and carrier proteins. The cleavage patterns were consistent with those of known plasma proteases, including initial cleavages by thrombin, plasmin and complement proteins, followed by aminopeptidase and carboxypeptidase activity. On the basis of these data, we discuss limitations in biomarker discovery in the low molecular weight plasma or serum proteome using crude fractionation coupled to MALDI-MS profiling.

Biomarkers↗