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Biomedical subjects

C X Yuan

Publications and source records attributed to C X Yuan.

16 recordsLinked to original sources
PubMed2001

[Studies on the sex difference in proteins between male and female adult worm of Schistosoma japonicum].

OBJECTIVE: To explore the sex difference in proteins between male and female adult worm of Schistosoma japonicum. METHODS: Two-electrophoresis was used to analyse the difference of protein between the male and female adult worm of S. japonicum (Chinese strain). RESULTS: Two-dimensional electrophoresis analysis revealed that at the site of 43 kDa and an isoelectric point (pI) of 5.60-5.90 the male worm exhibited a band carrying a number of spots and dots, being longer and wider than that exhibited by the female worm. The female worm exhibited 7 specific dots. CONCLUSION: The sex differences in proteins between male and female adult worms of S. japonicum are significant.

Animals↗
PubMed2000

Structural organization of yeast and mammalian mediator complexes.

Structures of yeast Mediator complex, of a related complex from mouse cells and of thyroid hormone receptor-associated protein complex from human cells have been determined by three-dimensional reconstruction from electron micrographs of single particles. All three complexes show a division in two parts, a "head" domain and a combined "middle-tail" domain. The head domains of the three complexes appear most similar and interact most closely with RNA polymerase II. The middle-tail domains show the greatest structural divergence and, in the case of the tail domain, may not interact with polymerase at all. Consistent with this structural divergence, analysis of a yeast Mediator mutant localizes subunits that are not conserved between yeast and mammalian cells to the tail domain. Biochemically defined Rgr1 and Srb4 modules of yeast Mediator are then assigned to the middle and head domains.

Animals↗
PubMed2000

Involvement of the TRAP220 component of the TRAP/SMCC coactivator complex in embryonic development and thyroid hormone action.

The TRAP220 component of the TRAP/SMCC complex, a mammalian homologof the yeast Mediator that shows diverse coactivation functions, interacts directly with nuclear receptors. Ablation of the murine Trap220 gene revealed that null mutants die during an early gestational stage with heart failure and exhibit impaired neuronal development with extensive apoptosis. Primary embryonic fibroblasts derived from null mutants show an impaired cell cycle regulation and a prominent decrease of thyroid hormone receptor function that is restored by ectopic TRAP220 but no defect in activation by Gal4-RARalpha/RXRalpha, p53, or VP16. Moreover, haploinsufficient animals show growth retardation, pituitary hypothyroidism, and widely impaired transcription in certain organs. These results indicate that TRAP220 is essential for a wide range of physiological processes but also that it has gene- and activator-selective functions.

Animals↗
PubMed2000

Plants contain a novel multi-member class of heat shock factors without transcriptional activator potential.

Based on phylogeny of DNA-binding domains and the organization of hydrophobic repeats, two families of heat shock transcription factors (HSFs) exist in plants. Class A HSFs are involved in the activation of the heat shock response, but the role of class B HSFs is not clear. When transcriptional activities of full-length HSFs were monitored in tobacco protoplasts, no class B HSFs from soybean or Arabidopsis showed activity under control or heat stress conditions. Additional assays confirmed the finding that the class B HSFs lacked the capacity to activate transcription. Fusion of a heterologous activation domain from human HSF1 (AD2) to the C-terminus of GmHSFB1-34 gave no evidence of synergistic enhancement of AD2 activity, which would be expected if weak activation domains were present. Furthermore, activity of AtHSFB1-4 (class B) was not rescued by coexpression with AtHSFA4-21 (class A) indicating that the class A HSF was not able to provide a missing function required for class B activity. The transcriptional activation potential of Arabidopsis AtHSFA4-21 was mapped primarily to a 39 amino acid fragment in the C-terminus enriched in bulky hydrophobic and acidic residues. Deletion mutagenesis of the C-terminal activator regions of tomato and Arabidopsis HSFs indicated that these plant HSFs lack heat-inducible regulatory regions analogous to those of mammalian HSF1. These findings suggest that heat shock regulation in plants may differ from metazoans by partitioning negative and positive functional domains onto separate HSF proteins. Class A HSFs are primarily responsible for stress-inducible activation of heat shock genes whereas some of the inert class B HSFs may be specialized for repression, or down-regulation, of the heat shock response.

Amino Acid Sequence↗
PubMed2000

Potential targets for HSF1 within the preinitiation complex.

Protein-protein interactions between human heat shock transcription factor 1 (hHSF1) and general transcription factors TFIIA-gamma, TFIIB, TBP, TAF(II)32, and TAF(II)55 and positive coactivator PC4 were characterized in order to identify potential targets of contact in the transcriptional preinitiation complex. These contacts represent one of the final steps in the signal transfer of heat stress to the transcriptional apparatus. TATA-binding protein (TBP) and transcription factor IIB (TFIIB) were identified as major targets for HSF1 transcriptional activation domains AD1 and AD2 based on in vitro interaction assays. TBP showed affinity for AD2 and a fragment containing AD1, while the core domain of TFIIB interacted primarily with the AD1 fragment. Interactions were also detected between full-length HSF1 and the small subunit (gamma) of TFIIA. PC4 interacted weakly with HSF2 and showed even less affinity for HSF1. Coimmunoprecipitation of transiently expressed TBP in HeLa cells demonstrated that HSF1 AD2 and AD1+AD2 are able to bind TBP in vivo. Assays based on transcriptional interference confirmed predictions that both TBP and TFIIB can interact with HSF1 activation domains in HeLa cells. The negative regulatory region (NR) of HSF1 did not interact with any general factors tested in vitro but did bind TFIID in nuclear extracts through contacts that probably involve TATA associated proteins (TAFs). These results suggest a model for transcriptional regulation by HSF1 that involves a shift between formation of dysfunctional TFIID complexes with the NR and transcriptionally competent complexes with the C-terminal activation domains.

Blotting, Western↗
PubMed1999

A novel human SRB/MED-containing cofactor complex, SMCC, involved in transcription regulation.

A novel human complex that can either repress activator-dependent transcription mediated by PC4, or, at limiting TFIIH, act synergistically with PC4 to enhance activator-dependent transcription has been purified. This complex contains homologs of a subset of yeast mediator/holoenzyme components (including SRB7, SRB10, SRB11, MED6, and RGR1), homologs of other yeast transcriptional regulatory factors (SOH1 and NUT2), and, significantly, some components (TRAP220, TRAP170/hRGR1, and TRAP100) of a human thyroid hormone receptor-associated coactivator complex. The complex shows direct activator interactions but, unlike yeast mediator, can act independently of the RNA polymerase II CTD. These findings demonstrate both positive and negative functional capabilities for the human complex, emphasize novel (CTD-independent) regulatory mechanisms, and link the complex to other human coactivator complexes.

Cloning, Molecular↗
PubMed1999

Identity between TRAP and SMCC complexes indicates novel pathways for the function of nuclear receptors and diverse mammalian activators.

The human thyroid hormone receptor-associated protein (TRAP) complex, an earlier described coactivator for nuclear receptors, and an SRB- and MED-containing cofactor complex (SMCC) that mediates activation by Gal4-p53 are shown to be virtually the same with respect to specific polypeptide subunits, coactivator functions, and mechanisms of action (activator interactions). In parallel with ligand-dependent interactions of nuclear receptors with the TRAP220 subunit, p53 and VP16 activation domains interact directly with a newly cloned TRAP80 subunit. These results indicate novel pathways for the function of nuclear receptors and other activators (p53 and VP16) through a common coactivator complex that is likely to target RNA polymerase II. Identification of the TRAP230 subunit as a previously predicted gene product also suggests a coactivator-related transcription defect in certain disease states.

Amino Acid Sequence↗
PubMed1998

The TRAP220 component of a thyroid hormone receptor- associated protein (TRAP) coactivator complex interacts directly with nuclear receptors in a ligand-dependent fashion.

Cognate cDNAs are described for 2 of the 10 thyroid hormone receptor-associated proteins (TRAPs) that are immunopurified with thyroid hormone receptor alpha (TRalpha) from ligand-treated HeLa (alpha-2) cells. Both TRAP220 and TRAP100 contain LXXLL domains found in other nuclear receptor-interacting proteins and both appear to reside in a single complex with other TRAPs (in the absence of TR). However, only TRAP220 shows a direct ligand-dependent interaction with TRalpha, and these interactions are mediated through the C terminus of TRalpha and (at least in part) the LXXLL domains of TRAP220. TRAP220 also interacts with other nuclear receptors [vitamin D receptor, retinoic acid receptor alpha, retinoid X receptor alpha, peroxisome proliferation-activated receptor (PPAR) alpha, PPARgamma and, to a lesser extent, estrogen receptor] in a ligand-dependent manner, whereas TRAP100 shows only marginal interactions with estrogen receptor, retinoid X receptor alpha, PPARalpha, and PPARgamma. Consistent with these results, TRAP220 moderately stimulates human TRalpha-mediated transcription in transfected cells, whereas a fragment containing the LXXLL motifs acts as a dominant negative inhibitor of nuclear receptor-mediated transcription both in transfected cells (TRalpha) and in cell free transcription systems (TRalpha and vitamin D receptor). These studies indicate that TRAP220 plays a major role in anchoring other TRAPs to TRalpha during the function of the TRalpha-TRAP complex and, further, that TRAP220 (possibly along with other TRAPs) may be a global coactivator for the nuclear receptor superfamily.

3T3 Cells↗
PubMed1998

Novel cofactors and TFIIA mediate functional core promoter selectivity by the human TAFII150-containing TFIID complex.

TATA-binding protein-associated factors (TAFIIs) within TFIID control differential gene transcription through interactions with both activators and core promoter elements. In particular, TAFII150 contributes to initiator-dependent transcription through an unknown mechanism. Here, we address whether TAFIIs within TFIID are sufficient, in conjunction with highly purified general transcription factors (GTFs), for differential core promoter-dependent transcription by RNA polymerase II and whether additional cofactors are required. We identify the human homologue of Drosophila TAFII150 through cognate cDNA cloning and show that it is a tightly associated component of human TFIID. More importantly, we demonstrate that the human TAFII150-containing TFIID complex is not sufficient, in the context of all purified GTFs and RNA polymerase II, to mediate transcription synergism between TATA and initiator elements and initiator-directed transcription from a TAFII-dependent TATA-less promoter. Therefore, TAFII-promoter interactions are not sufficient for the productive core promoter-selective functions of TFIID. Consistent with this finding, we have partially purified novel cofactor activities (TICs) that potentiate the TAFII-mediated synergism between TATA and initiator elements (TIC-1) and TAFII-dependent transcription from TATA-less promoters (TIC-2 and -3). Furthermore, we demonstrate an essential function for TFIIA in TIC- and TAFII-dependent basal transcription from a TATA-less promoter. Our results reveal a parallel between the basal transcription activity of TAFIIs through core promoter elements and TAFII-dependent activator function.

ARNTL Transcription Factors↗
PubMed1997

Expression of human heat shock transcription factors 1 and 2 in HeLa cells and yeast.

We have examined reporter gene (beta-gal) expression directed by human heat shock transcription factors 1 and 2 (HSF1 and HSF2) in HeLa cells and in yeast (Saccharomyces cerevisiae). Transcriptional activation domains of both HSFs were mapped to the C-termini using chimeric proteins containing the GAL4 DNA binding domain (GAL4-DBD). Deletion analysis of HSF1 largely confirmed the mapping and expression pattern of activation domain 2 (AD2) previously reported by Green et al (1995) with the exception of the contribution of the oligomerization domain (hydrophobic region A) to basal repression in yeast, but not in HeLa cells. In addition, a C-terminal activation domain for HSF2 (amino acids 397 to 536) was identified by analysis in yeast. In contrast to HSF1, full length HSF2 and the isolated activation domain of HSF2 showed little activity in HeLa cells. Analysis of point mutations generated by low fidelity PCR within AD2 of HSF1 indicated that hydrophobic and charged amino acids in addition to proline, serine and threonine make critical contributions to transcriptional activity. Co-expression of GAL4-DBD fusions with AD2 of HSF1 and the C-terminal activation domain of HSF2 showed no evidence of synergism in the activation of transcription. Wild-type human HSF1 and HSF2 were both able to substitute for the endogenous yeast HSF under normal growth conditions.

Cell Line↗
PubMed1995

Isolation and characterization of six heat shock transcription factor cDNA clones from soybean.

Thermal stress in soybean seedlings causes the activation of pre-existing heat shock transcription factor proteins (HSFs). Activation results in the induction of DNA binding activity which leads to the transcription of heat shock genes. From a soybean cDNA library we have isolated cDNA clones corresponding to six HSF genes. Two HSF genes are expressed constitutively at the transcriptional level, and the remaining four are heat-inducible. Two of the heat inducible genes are also responsive to cadmium stress. Comparative analysis of HSF sequences indicated higher conservation of the DNA binding domain among plant HSFs than those from yeast or other higher eukaryotes. The putative plant HSF oligomerization domain contains hydrophobic heptapeptide repeats characteristic of coiled coils and seems to exist in two structural variants. The carboxy-terminal domains are reduced in size and the C-terminal heptad repeat is degenerate.

Amino Acid Sequence↗
PubMed1994

[Hepatopetal blood occlusion of half liver during hepatectomy in 29 patients].

In this study, hepatectomy was performed in 29 cases by temporarily occluding hepatopetal blood flow of only the half liver where the cancer was located. Results were compared with that of total hepatopetal blood occlusion in 14 cases. It was found that this method was less of postoperative complications, especially in cases with liver cirrhosis, and easy to perform.

Adult↗
PubMed1989

Observations on clinical therapeutic effect in treating soft tissue injuries by acupuncture, with pain threshold and electromyography as parameters.

360 observations were made on 120 cases of soft tissue injury divided into groups. 1. Among the 100 patients in the acupuncture treatment group, 300 observations were made; among the 20 controls there were 60 observations. The effective rate in the acupuncture treatment group was 85.00%; in the control group it was 41.67%, a very significant difference (P less than 0.01). 2. Relationship between therapeutic course and effect. The effective rate for the first course was 74.00%; it was 90.50% when more than two courses were given, a very significant difference (P less than 0.01) indicating the marked effect of acupuncture treatment. 3. Based on the therapeutic theory of TCM syndrome differentiation and reinforcement method in the asthenia state, and reducing method in asthenia state, different manipulations were used for asthenia-heat and asthenia-cold types with good clinical results. There was no significant difference (P greater than 0.05) between the effective rate in these two types, pointing up the significance of the TCM syndrome differentiation theory in clinical acupuncture. 4. There was very significant difference (P less than 0.01) in the degree of pressed pain on the patient's tender spot before and after acupuncture treatment, also (P less than 0.01 and P less than 0.001 respectively) in the EMG amplitude on the affected side of the lumbar area before and after acupuncture treatment during light and heavy force in extension action of back muscles. Acupuncture treatment on soft tissue disease based on TCM syndrome differentiation theory is thus shown to be effective.

Acupuncture Therapy↗