Publications (6) View all
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Article: G-actin participates in RNA polymerase II-dependent transcription elongation by recruiting positive transcription elongation factor b (P-TEFb).
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ABSTRACT: Actin is a key regulator of RNA polymerase (Pol) II-dependent transcription. Positive transcription elongation factor b (P-TEFb), a Cdk9/cyclin T1 heterodimer, has been reported to play a critical role in transcription elongation. However, the relationship between actin and P-TEFb is still not clear. In this study, actin was found to interact with Cdk9, a catalytic subunit of P-TEFb, in elongation complexes. Using immunofluorescence and immunoprecipitation assays, Cdk9 was found to bind to G-actin through the conserved Thr-186 in the T-loop. Overexpression and in vitro kinase assays showed that G-actin promotes P-TEFb-dependent phosphorylation of the Pol II C-terminal domain. An in vitro transcription experiment revealed that the interaction between G-actin and Cdk9 stimulated Pol II transcription elongation. ChIP and immobilized template assays indicated that actin recruited Cdk9 to a transcriptional template in vivo and in vitro. Using cytokine IL-6-inducible p21 gene expression system, we revealed that actin recruited Cdk9 to endogenous gene. Moreover, overexpression of actin and Cdk9 increased histone H3 acetylation and acetylized histone H3 binding to a transcriptional template through the interaction with histone acetyltransferase, p300. Taken together, our results suggested that actin participates in transcription elongation by recruiting Cdk9 for phosphorylation of the Pol II C-terminal domain, and the actin-Cdk9 interaction promotes chromatin remodeling.Journal of Biological Chemistry 03/2011; 286(17):15171-81. · 4.77 Impact Factor -
Article: Disturbance in function and expression of condensin affects chromosome compaction in HeLa cells.
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ABSTRACT: Condensin, a major non-histone protein complex on chromosomes, is responsible for the formation of rod-shaped chromosome in mitosis. A heterodimer composed of SMC2 (structural maintenance of chromosomes) and SMC4 subunits constitutes the core part of condensin. Although extensive studies have been done in yeast, fruit fly and Xenopus to uncover the mechanisms and molecular nature of SMC proteins, little is known about the complex in mammalian cells. We have conducted a series of experiments to unveil the nature of condensin complex in human chromosome formation. The results show that overexpression of the C-terminal domain of SMC subunits disturbs chromosome condensation, leading to formation of swollen chromosomes, while knockdown of SMC subunits severely disturbs mitotic chromosome formation, resulting in chromatin bridges between daughter cells and multiple nuclei in single cells. The salt extraction assay indicates that a fraction of the condensin complex is bound to chromatin in interphase, but most of the condensin bind to chromatin at the onset of mitosis. Thus, disturbance in condensin function or expression affects chromosome condensation and influences mitotic progression.Cell Biology International 03/2011; 35(7):735-40. · 1.48 Impact Factor -
Article: RNA helicase A acts as a bridging factor linking nuclear beta-actin with RNA polymerase II.
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ABSTRACT: Actin, the major component of the cytoplasmic skeleton, has been shown to exist in the nucleus. Nuclear actin functions in several steps of the transcription process, including chromatin remodelling and transcription initiation and elongation. However, as a part of PICs (pre-initiation complexes), the role of actin remains to be elucidated. In the present study, we identified RHA (RNA helicase A) as an actin-interacting protein in PICs. Using immunoprecipitation and immunofluorescence techniques, we have shown that RHA associates with beta-actin in the nucleus. A GST (glutathione transferase) pulldown assay using different deletion mutants revealed that the RGG (Arg-Gly-Gly) region of RHA was responsible for the interaction with beta-actin, and this dominant-negative mutant reduced the recruitment of Pol II (RNA polymerase II) into PICs. Moreover, overexpression or depletion of RHA could influence the interaction of Pol II with beta-actin and beta-actin-involved gene transcription regulation. These results suggest that RHA acts as a bridging factor linking nuclear beta-actin with Pol II.Biochemical Journal 04/2009; 420(3):421-8. · 4.90 Impact Factor -
Article: BAF53 interacts with p53 and functions in p53-mediated p21-gene transcription.
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ABSTRACT: BAF53, a component of chromatin remodelling and histone acetyltransferase complexes, has been shown to be essential for cell survival in human cells and plays roles in p53-mediated gene transcription. However, the mechanism concerned in the process needs to be further explored. In this study, we show that BAF53 is involved in the repression of p53-dependent p21-gene transcription by interacting with p53 both in vivo and in vitro. Through electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation analyses, we demonstrate that BAF53 can reduce the p53-binding ability to p21 promoter. By western-blot experiments, we find that BAF53 can decrease p53-Lys382 acetylation, which may be partially responsible for the repression of p53-binding ability. Furthermore, BAF53 represses p21-promoter activity in a BRG1-independent manner. These data contribute to elucidating the molecular mechanisms of BAF53 in regulating p53-mediated gene transcription.Journal of Biochemistry 12/2007; 142(5):613-20. · 2.37 Impact Factor -
Article: c-Abl tyrosine kinase activates p21 transcription via interaction with p53.
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ABSTRACT: c-Abl non-receptor tyrosine kinase has been implicated in many cellular processes including cell differentiation, stress response and regulating gene transcription. The mechanism by which c-Abl is involved in the regulation of gene transcription remains to be elucidated. In this study, we investigated the functions of c-Abl in the activation of p21 promoter. Our results showed that overexpression of c-Abl tyrosine kinase activated p21 promoter and endogenous p21 transcription in U2OS cells. We found that p53 is involved in the activation of p21 promoter by c-Abl, and integrative structure of p53 is required for regulating p21 transcription. In addition, the chromatin immunoprecipitation study demonstrated that c-Abl and p53 can be recruited to the region containing p53 binding site of p21 promoter, and c-Abl increases the DNA binding activity of p53 to the p21 promoter. Furthermore, not only the activation of p21 promoter but also the recruitment to p21 promoter by c-Abl is dependent on the interaction between c-Abl and p53 protein.Journal of Biochemistry 06/2007; 141(5):621-6. · 2.37 Impact Factor
