Binding of FoxM1 to G2/M gene promoters is dependent upon B-Myb
Binding of FoxM1 to G2/M gene promoters is dependent upon B-Myb
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DOI：
10.1016/j.bbagrm.2012.03.008
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发表时间：
2012-08-01
影响因子：
4.7
通讯作者：
Watson, Roger J.
中科院分区：
文献类型：
--
作者：
Down, Christin F.;Millour, Julie;Watson, Roger J.
调控有丝分裂进入和进展的基因启动子通常在G2中被包括B-Myb和FoxM1在内的转录因子最大限度地诱导。由于FoxM1基因转录是B-Myb的靶标，我们在本研究中研究了这些转录因子如何在功能上相互作用以调节这些G2/M基因。我们使用含有可被Cre重组酶有条件地删除的flxed B-myb等位基因（B-myb(F/F)）的3T3细胞系，证实B-myb敲除导致包括FoxM1在内的几个G2/M基因mRNA表达降低，并延迟进入有丝分裂。虽然当静止的B-myb(F/F) 3T3细胞在血清刺激下重新进入细胞周期时，FoxM1蛋白的表达实际上不受B-myb敲除的影响，但染色质免疫沉淀显示FoxM1与G2/M启动子的结合显著降低。FoxM1的转录活性需要周期蛋白依赖激酶和Plk1的顺序磷酸化，Plk1是B-Myb的靶基因，我们发现在敲除B-Myb后，Plk1特异性位点的磷酸化程度有所降低。然而，无论是这种效应，还是不受B-myb敲除影响的FoxM1的核积累，都不足以解释FoxM1启动子结合依赖于B-myb。更重要的是，使用野生型或突变Myb结合位点的配对Birc5 （survivin）启动子-荧光素酶报告子进行的实验表明，在没有B-Myb结合的情况下，FoxM1无法结合和激活启动子。我们的数据表明，B-Myb是FoxM1与G2/M基因启动子结合所需的先驱因子，并解释了这些转录因子如何协同诱导有丝分裂。(C) 2012 Elsevier B.V.版权所有
The promoters of genes which regulate entry into and progress through mitosis are typically induced maximally in G2 by transcription factors that include B-Myb and FoxM1. As FoxM1 gene transcription is a target of B-Myb, we investigated in this study how these transcription factors functionally interact to regulate these G2/M genes. Using a 3T3 cell line containing floxed B-myb alleles (B-myb(F/F)) that could be conditionally deleted by Cre recombinase, we confirmed that B-myb knockout caused both decreased mRNA expression of several G2/M genes, including FoxM1, and delayed entry into mitosis. Although FoxM1 protein expression was actually unaffected by B-myb knockout when quiescent B-myb(F/F) 3T3 cells re-entered the cell cycle upon serum-stimulation, chromatin immunoprecipitation revealed that FoxM1 binding to G2/M promoters was substantially reduced. FoxM1 transcriptional activity requires sequential phosphorylation by Cyclin-dependent kinases and Plk1, which are B-Myb target genes, and we found that phosphorylation at Plk1-specific sites was somewhat reduced upon B-myb knockout. Neither this effect nor nuclear accumulation of FoxM1, which was unaffected by B-myb knockout, was sufficient to account for the dependence on B-Myb for FoxM1 promoter binding, however. More significantly, assays using paired Birc5 (survivin) promoter-luciferase reporters with either wild-type or mutated Myb binding sites showed that FoxM1 was unable to bind and activate the promoter in the absence of B-Myb binding. Our data suggest that B-Myb is required as a pioneer factor to enable FoxM1 binding to G2/M gene promoters and explains how these transcription factors may collaborate to induce mitosis. (C) 2012 Elsevier B.V. All rights reserved.