Crighton Diane, Woiwode Annette, Zhang Cheng, Mandavia Nihar, Morton Jennifer P, Warnock Lorna J, Milner Jo, White Robert J, Johnson Deborah L
Institute of Biomedical and Life Sciences, Division of Biochemistry and Molecular Biology, Davidson Building, University of Glasgow, Glasgow G12 8QQ, UK.
EMBO J. 2003 Jun 2;22(11):2810-20. doi: 10.1093/emboj/cdg265.
The tumor suppressor p53 is a transcription factor that controls cellular growth and proliferation. p53 targets include RNA polymerase (pol) III-dependent genes encoding untranslated RNAs such as tRNA and 5S rRNA. These genes are repressed through interaction of p53 with TFIIIB, a TATA-binding protein (TBP)-containing factor. Although many studies have shown that p53 binds to TBP, the significance of this interaction has remained elusive. Here we demonstrate that the TBP-p53 interaction is of functional importance for regulating RNA pol III-transcribed genes. Unlike RNA pol II-dependent promoter repression, overexpressing TBP can reverse inhibition of tRNA gene transcription by p53. p53 does not disrupt the direct interaction between the TFIIIB subunits TBP and Brf1, but prevents the association of Brf1 complexes with TFIIIC2 and RNA pol III. Using chromatin immunoprecipitation assays, we found that TFIIIB occupancy on tRNA genes markedly decreases following p53 induction, whereas binding of TFIIIC2 to these genes is unaffected. Together our results support the idea that p53 represses RNA pol III transcription through direct interactions with TBP, preventing promoter occupancy by TFIIIB.
肿瘤抑制因子p53是一种控制细胞生长和增殖的转录因子。p53的靶标包括编码非翻译RNA（如tRNA和5S rRNA）的RNA聚合酶（pol）III依赖性基因。这些基因通过p53与TFIIIB（一种含TATA结合蛋白（TBP）的因子）的相互作用而受到抑制。尽管许多研究表明p53与TBP结合，但这种相互作用的意义仍然难以捉摸。在这里，我们证明TBP-p53相互作用对于调节RNA pol III转录的基因具有功能重要性。与RNA pol II依赖性启动子抑制不同，过表达TBP可以逆转p53对tRNA基因转录的抑制作用。p53不会破坏TFIIIB亚基TBP和Brf1之间的直接相互作用，但会阻止Brf1复合物与TFIIIC2和RNA pol III的结合。使用染色质免疫沉淀分析，我们发现p53诱导后，tRNA基因上的TFIIIB占有率显著降低，而TFIIIC2与这些基因的结合不受影响。我们的结果共同支持了这样一种观点，即p53通过与TBP的直接相互作用抑制RNA pol III转录，从而阻止TFIIIB占据启动子。
