T细胞蛋白p80调控c-Myc表达的机理

The mechanism of c-Myc expression regulated by T cell protein p80

摘要:

为了解p80在正常T细胞以及T细胞癌变过程中的作用，在缺失p80的T淋巴瘤细胞中重新表达p80，其结果显示：原癌基因c-Myc的表达受到显著抑制，且细胞周期在G1期出现了停滞.定量PCR的结果表明：p80 对c-Myc表达的抑制是转录水平的抑制.双荧光素酶报告基因试验表明：p80对c-Myc的抑制作用定位于c-Myc启动子上相对于转录起始位点的-1042bp~-630bp区域.运用TFSEARCH软件对这一区域的分析发现存在多个c-Myb结合位点.在稳定表达p80的T淋巴癌细胞中敲低c-Myb，表明p80对c-Myc的转录抑制是通过cMyb来实现的.免疫共沉淀实验表明p80和c-Myb在细胞中存在相互作用.进一步的研究显示p80对c-Myc的转录抑制依赖于组蛋白去乙酰化酶的活性.研究结果表明p80有可能通过与c-Myb的相互作用将组蛋白去乙酰化酶募集至c-Myc启动子区域，并通过组蛋白的去乙酰化抑制c-Myc的表达.

Abstract:

Our experimental data indicate that overexpression of p80 in p80 null T cell leukemia cells significantly down regulates c-Myc oncoprotein and blocks cell cycle progression from G1 to S phase. The qPCR examination and protein stability test found that p80 regulates expression of c-Myc at the transcriptional level. The analysis of c-Myc promoter activity at the presence of p80 by Dual Luciferase Reporter Assay indicated that the transcriptional repression of p80 on c-Myc promoter is located at -1042bp~-630bp above the transcription start site of cMyc gene. The transcription factor binding sites search of this region by software TFSEARCH revealed multiple binding sequences of c-Myb, another oncoprotein and transcription factor which plays an important role in the proliferation and differentiation of blood cells during hematopoiesis. Knockdown c-Myb in MOLT-4 cells stably expressing p80 indicate that p80 suppresses the transcription of c-Myc gene through c-Myb. Co-immunoprecipitation experiment demonstrated that p80 interacts with c-Myb inside cells. The further experiment has shown that transcriptional repression of c-Myc by p80 is dependent on the enzymatic activity of histone deacetylase. Taken together, our results suggest that p80 recruits histone deacetylase to the c-Myc promoter through interaction with transcription factor c-Myb, and p80 suppresses c-Myc expression by histone deacetylation.