Biomedical subjects

Shan Yan

Publications and source records attributed to Shan Yan.

7 recordsLinked to original sources

PubMed2006

Direct requirement for Xmus101 in ATR-mediated phosphorylation of Claspin bound Chk1 during checkpoint signaling.

TopBP1-like proteins, which include Xenopus laevis Xmus101, are required for DNA replication and have been linked to replication checkpoint control. A direct role for TopBP1/Mus101 in checkpoint control has been difficult to prove, however, because of the requirement for replication in generating the DNA structures that activate the checkpoint. Checkpoint activation occurs in X. laevis egg extracts upon addition of an oligonucleotide duplex (AT70). We show that AT70 bypasses the requirement for replication in checkpoint activation. We take advantage of this replication-independent checkpoint system to determine the role of Xmus101 in the checkpoint. We find that Xmus101 is essential for AT70-mediated checkpoint signaling and that it functions to promote phosphorylation of Claspin bound Chk1 by the ataxia-telangiectasia and Rad-3-related (ATR) protein kinase. We also identify a separation-of-function mutant of Xmus101. In extracts expressing this mutant, replication of sperm chromatin occurs normally; however, the checkpoint response to stalled replication forks fails. These data demonstrate that Xmus101 functions directly during signal relay from ATR to Chk1.

Adaptor Proteins, Signal Transducing↗

PubMed2004

[Supraorbital keyhole approach for microsurgical treatment of aneurysms in the anterior circulation].

OBJECTIVE: To study the method with endoscope-assisted microsurgical technique through the supraorbital keyhole approach to treat aneurysms in the anterior circulation. METHODS: According to preoperative diagnostic imagings, to work out of the individual operation planning. Skin incision was made in the eyebrow, and the diameter of supraorbital craniotomy was about 2 cm, endoscope-assisted microsurgical technique was used to clip aneurysm. The technique was used in the most recent 12 consecutive patients. RESULTS: Five different kinds of aneurysms in the anterior circulation were clipped through this method and 12 patients were cured. One patient, intraoperative accidental aneurysm rupture occurred. There were no approach-related complications. CONCLUSIONS: This endoscope-assisted microsurgical technique via supraorbital keyhole approach is a safe, minimal invasive and effective way for the treatment of aneurysms in the anterior circulation, and there is more sufficient operating space.

Adult↗

PubMed2004

Temperature may influence and regulate NF-YB expression in toad oocyte.

Fully grown oocytes derived from Bufo gargarizans maintained at relatively low temperatures (4 degrees C, LTE-oocytes) acquire the competence to resume normal meiosis. In contrast, fully grown oocytes derived from toads maintained at relatively high temperatures (28 degrees C, HTE-oocytes) never acquire maturation competence. By suppression subtractive hybridization, we obtained 18 ESTs preliminarily thought to be preferentially expressed in LTE-oocytes; of these, TS1-4 shared homology with the human and mouse NF-YB genes. We cloned the full-length toad NF-YB gene by RACE and identified three alternatively spliced transcripts: tNF-YB1, tNF-YB2, and tNF-YB3 (GenBank Accession Nos. AY442015, AY442016, and AY442017, respectively). Toad NF-YB was differentially transcribed and translated in LTE-oocytes versus HTE-oocytes, likely resulting in differential CCAAT-binding and/or transcriptional activity of NF-Y. Furthermore, toad cyclin B2 was differentially transcribed at high and low temperatures. Taken together, this report of the differential expression of toad NF-YB at different temperatures is the first evidence that temperature may influence and regulate NF-YB expression.

Alternative Splicing↗

PubMed2003

[The functions in the progesterone-induced oocyte maturation of toad ubiquitin carboxyl-terminal hydrolase (tUCH) is independent of its UCH activity].

p28, a protein derived from toad (Bufo bufo gargarizans) oocytes, has a high level of sequence homology to mouse UCH L1. We report here that it is a toad ubiquitin carboxyl-terminal hydrolase (UCH), termed tUCH for its ability to hydrolyze the UCH substrate ubiquitin ethyl ester (UboEt). The similarities of secondary structures between tUCH and UCH L1 highlight that they might have common functions. The total extracted proteins both from immature and matured oocytes contain 2% tUCH. The enzyme kinetic constants (Km and Kc) both of the tUCH and UCH L1 reveal that they possess similar catalytic properties on their common substrate Ub-AMC. Anti-tUCH monoclonal antibody (tUCH mAb) can recognize tUCH and dominant-negative tUCH (tUCH C(90)S), but not mouse UCH L1, suggesting that it does not target on the conservative UCH active sites. Furthermore, anti-tUCH mAb when injected into oocytes blocked the progesterone-induced GVBD but anti-tUCH mAb could not inhibit the tUCH catalytic hydrolysis of Ub-AMC, revealing that the implication of tUCH in the oocyte maturation regulation is not dependent on its UCH activity.

Amino Acid Sequence↗

PubMed2003

[Endoscope-assisted supraorbital keyhole approach for excision of suprasellar region tumor].

OBJECTIVE: To study endoscope-assisted microsurgical technique with supraorbital keyhole approach for the treatment of suprasellar region tumor so as to maximize tumor removal and minimize operative-trauma. METHODS: According to high resolution CT and MR images before operation, individual operation schemes were worked out. Skin incision was made in the eyebrow, and the diameter of supraorbital craniotomy was approximately 2 cm. Endoscope-assisted microsurgical technique was used to resect lesions in 16 consecutive patients. RESULTS: Total Tumors were removed in all of the 16 patients via the supraorbital keyhole approach. No postoperative complications occurred. CONCLUSIONS: Supraorbital keyhole approach may diminish tissue injury considerably and has proven to provide sufficient operating space in the suprasellar region for tumor removal.

Adolescent↗

PubMed2002

[Developmental stage-dependence of cyclin B1 protein localization and gene expression in rabbit spermatogenesis].

By means of in situ hybridization and immunohistochemistry, the protein localization and gene expression of cyclin B1 in spermatogenic cells were characterized during the spermatogenesis of rabbits. The results showed that the cyclin B1 mRNA in rabbit spermatogenic epithelium was expressed dominantly in primary spermatocytes. The expression was observed in round spermatids with a gradual decline in the process of metamorphosis of the spermatids, but not in elongated spermatids and sperms. Cyclin B1 protein was expressed in mitotic spermatogonia and meiotic spermatocytes and was observed predominantly in round and elongated spermatids. These results indicate that the expression of cyclin B1 mRNA and localization of cyclin B1 protein are dependent on the developmental stages of spermatogenic cells.

Animals↗

PubMed2002

A novel ubiquitin carboxyl terminal hydrolase is involved in toad oocyte maturation.

p28, a 28kD protein from toad (Bufo bufo gargarizans) oocytes, was identified by using p13(suc1)-agarose affinity chromatography. Sequence homology analysis of the full-length cDNA of p28 (Gene Bank accession number: AF 314091) indicated that it encodes a protein containing 224 amino-acids with about 55% identities and more than 70% positives to human, rat or mouse UCH-L1, and contains homological functional domains of UCH family. Anti-p28 monoclonal antibody, on injecting into the oocytes, could inhibit the progesterone-induced resumption of meiotic division in a dose-dependent manner. The recombinant protein p28 showed similar SDS/PAGE behaviors to the native one, and promoted ubiquitin ethyl ester hydrolysis, a classical catalytic reaction for ubiquitin carboxyl terminal hydrolases (UCHs). The results in this paper reveal that a novel protein, p28, exists in the toad oocytes, is a UCH L1 homolog, was engaged in the process of progesterone-induced oocyte maturation possibly through an involvement in protein turnover and degradation.

Amino Acid Sequence↗