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Yu Zhang,
Yanyan Gao, Guoping Zhang,
Shuyan Huang,
Zhixiong Dong,
Chenfei Kong,
Dongmei Su,
Juan Du,
Shan Zhu,
Qian Liang,
Jianchao Zhang,
Jun Lu,
Baiqu Huang
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ABSTRACT: The DNA-damaging drug doxorubicin (Dox) induces cell senescence at concentrations significantly lower than those required for induction of apoptosis. At low Dox concentrations, tumor suppressor p53 is activated, which enhances the expression of p21(Waf1/Cip1) (p21). At high concentrations, Dox activates p53 leading to apoptosis without enhancing p21 expression. The underlying mechanisms and factors that govern the differential effects of Dox in inducing senescence and apoptosis are unclear. Here, we report that the DNA methyltransferase (DNMT) DNMT3a was upregulated by Dox especially at concentrations that induced apoptosis in HCT116 colorectal cancer cells, and this process was regulated by p53. Meanwhile, p21 expression was significantly upregulated at senescence-inducing concentrations and kept low on treatment with apoptosis-inducing concentrations of Dox. The differential expression of DNMT3a and p21 in response to Dox suggests that DNMT3a may be a key factor in switches between Dox-induced senescence and apoptosis. Moreover, when DNMT3a was silenced, treatment of HCT116 cells with apoptosis-inducing concentration of Dox increased the percentage of cells undergoing senescence, accompanied by upregulation of p21. Contrarily, senescence-inducing concentration of Dox promoted apoptosis rate, and p21 expression was repressed. Surprisingly, no changes in DNA methylation status at p21 promoter were detected at either ranges of Dox, although DNMT3a and HDAC1 were recruited to p21 promoter at apoptosis-inducing Dox concentration, where they were present in the same complex. Overall, these data demonstrate that DNMT3a impacts the expression of p21 and plays a role in determining the Dox-induced senescence and apoptosis in HCT116 cells.
International Journal of Cancer 02/2011; 128(3):551-61. · 5.44 Impact Factor
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ABSTRACT: Histone deacetylase inhibitor sodium butyrate (NaBu) can induce G(0)/G(1) arrest and erythroid differentiation in K562 cells, but the molecular mechanisms underlying this process are unclear. Here we show that both p18( INK4C ) mRNA and protein levels were upregulated during K562 cell erythroid differentiation induced by NaBu. Moreover, the NaBu activation of p18( INK4C ) was dependent on the integrity of Sp1 clusters in the promoter. NaBu caused hyperacetylation of histones H3 and H4 on endogenous p18( INK4C ) promoter and enhanced binding of transcription factor Sp1 in vivo. Also, overexpression of p18( INK4C ) in K562 cells resulted in G(0)/G(1) arrest and partial erythroid differentiation. Our results suggested that NaBu-mediated p18( INK4C ) regulation played a role in cell cycle arrest and erythroid differentiation in K562 cells.
Molecular and Cellular Biochemistry 12/2008; 319(1-2):9-15. · 2.06 Impact Factor
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ABSTRACT: To validate the involvement of reversible histone acetylation in the transcriptional regulation of human Wilms' tumor 1 gene (WT1), we analyzed the roles of histone deacetylases (HDACs) and histone acetyltransferase in this epigenetic process. Of the six HDACs (HDAC1-6) examined, HDAC4 and HDAC5 were found to have significant repressing effects on the activity of the WT1 reporter gene, as revealed by luciferase reporter assays and quantitative real-time reverse transcription-polymerase chain reaction assays. Luciferase reporter assays showed that the histone acetyltransferase p300 was able to counteract the HDAC4/HDAC5-mediated repression and that p300/CBP synergized with transcription factors Sp1, c-Myb, and Ets-1 in activation of the WT1 reporter. Chromatin immunoprecipitation experiments showed that p300 promotes the acetylation level of histone H3 at the WT1 intronic enhancer. Based on these data, we proposed a hypothetical model for the involvement of reversible histone acetylation in transcriptional regulation of the WT1 gene. This study provides further insight into the mechanisms of transcriptional regulation of the WT1 gene and WT1-associated diseases treatment.
Acta Biochimica et Biophysica Sinica 01/2008; 39(12):931-8. · 1.38 Impact Factor
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ABSTRACT: Functions of the Elp3 subunit of the recently purified human Elongator were studied using an in vivo yeast complementation system. We demonstrated that the human ELP3 gene (hELP3) was able partially to complement functional defects of yeast elp3Delta cells. Furthermore, a chimeric ELP3 gene (yhELP3) encoding a protein in which the putative histone acetyltransferase (HAT) domain of hELP3 fused to the remainder of the yeast Elp3p corrected the growth defects of elp3Delta cells and complemented the slow activation of some inducible genes. Moreover, deletion of the B motif of the catalytic domain of the HAT region of hELP3 eliminated the ability of yhELP3 to complement elp3Delta in vivo, indicating that the HAT activity is essential for ELP3 function. We also demonstrated that replacement of specific lysine residues in histones H3 and H4 by arginine affected the complementation capacity of both the yeast gene (yELP3) and the chimeric yhELP3 in the elp3Deltastrain. Specifically, mutation of lysine-14 of H3 (H3 K14R) or lysine-8 of H4 (H4 K8R) reduced the ability of yELP3 and yhELP3 to complement the elp3Delta mutant, whereas simultaneous mutation of both sites (H3 K14R/H4 K8R) almost completely abolished complementation. These results imply a link between the acetylation of specific sites in nucleosomal histones and the regulation of transcription elongation by human Elp3. The data presented in this report suggest that the Elp3 subunits of human and yeast are highly conserved in their structure and functions.
Molecular and General Genetics 06/2005; 273(3):264-72. · 2.63 Impact Factor
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ABSTRACT: The Wilms' tumor gene-1 (WT1) encodes a zinc finger protein involved in gene regulation during kidney, gonad, and heart development. In addition to its promoter, a 258 bp intronic enhancer is required for tissue-specific expression of WT1 gene. p300 is a histone acetyltransferase (HAT) and exerts essential functions in gene regulation. Here, we show that p300 increased the expression of endogenous WT1 mRNA and promoted the activation of the WT1 promoter and intronic enhancer. The results also revealed that the adenovirus E1A repressed the p300 function, while the p300-binding defective E1A delta 2-36 did not, and p300 HAT activity was important for its function since p300 mutant with the HAT domain deleted partially abrogated its ability to activate the WT1 promoter and intronic enhancer. Furthermore, p300 and c-Myb synergistically activated the expression of WT1 gene. This study revealed that p300 and its HAT activity were involved in regulation of WT1 transcription.
Archives of Biochemistry and Biophysics 05/2005; 436(1):62-8. · 2.93 Impact Factor
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ABSTRACT: p300/CBP are versatile transcriptional coactivators that participate in many physiological processes, including cell cycle
control, differentiation and apoptosis. p300/CBP possess histone acetyltransferase (HAT) activity and they are involved in
transcriptional regulation by acetylating histone and nonhistone proteins. Moreover, they act as protein bridges connecting
specific transcription factors to the basal transcription machinery and provide a scaffold to integrate multiple transcription
cofactors. Several studies suggest that p300/CBP may serve as tumor suppressors since mutations or translocations in p300/Cbp genes have been observed in a number of cancers. Furthermore, in many neurodegenerative diseases, inhibition of p300/CBP
function may be one of the underlying causes of cytotoxicity. Several studies have demonstrated that p300/CBP are implicated
in the regulation of many interleukin genes. This review focuses on the structures and functions of p300/CBP and their roles
in the regulation of interleukin genes based on the work performed in our laboratory.
Chinese Science Bulletin 11/2004; 49(24):2555-2562. · 1.32 Impact Factor
