ERK phosphorylation of MED14 in promoter complexes during mitogen-induced gene activation by Elk-1.
ERK phosphorylation of MED14 in promoter complexes during mitogen-induced gene activation by Elk-1.
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DOI：
10.1093/nar/gkt837
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发表时间：
2013-12
影响因子：
14.9
通讯作者：
Shaw PE
中科院分区：
文献类型：
--
作者：
Galbraith MD;Saxton J;Li L;Shelton SJ;Zhang H;Espinosa JM;Shaw PE
ETS结构域转录因子Elk-1刺激响应于有丝分裂原的立即早期基因（IEG）的表达。这些事件需要通过细胞外信号调节激酶（ERK）磷酸化Elk-1以及Elk-1与辅激活剂（包括组蛋白乙酰转移酶和介体复合物）的磷酸化依赖性相互作用。Elk-1还将ERK募集到其靶基因的启动子，表明ERK在有丝分裂原应答启动子处磷酸化转录复合物中的额外底物。在这里，我们报告说，MED 14，一个核心亚基的调解人，是一个真正的ERK底物，并确定丝氨酸986（S986）内的丝氨酸脯氨酸丰富的区域MED 14作为主要的ERK磷酸化位点。有丝分裂原诱导S986上IEG启动子处MED 14的磷酸化; MED 14的RNAi敲除减少CDK 8和RNA聚合酶II（RNAPII）募集、RNAPII C-末端结构域磷酸化和IEG转录的受损活化。在S986处的单个丙氨酸取代减少了致癌Ras和有丝分裂原诱导的Elk-1依赖性转录对E26（ETS）响应性报告基因的激活，而其他转录激活因子的活性不受影响。我们还证明了Elk-1可以独立于MED 23与MED 14相关联，这可能有助于ERK对MED 14的磷酸化，从而对有丝分裂原应答基因表达产生积极和选择性的影响。
The ETS domain transcription factor Elk-1 stimulates expression of immediate early genes (IEGs) in response to mitogens. These events require phosphorylation of Elk-1 by extracellular signal-regulated kinase (ERK) and phosphorylation-dependent interaction of Elk-1 with co-activators, including histone acetyltransferases and the Mediator complex. Elk-1 also recruits ERK to the promoters of its target genes, suggesting that ERK phosphorylates additional substrates in transcription complexes at mitogen-responsive promoters. Here we report that MED14, a core subunit of the Mediator, is a bona fide ERK substrate and identify serine 986 (S986) within a serine-proline rich region of MED14 as the major ERK phosphorylation site. Mitogens induced phosphorylation of MED14 on S986 at IEG promoters; RNAi knockdown of MED14 reduced CDK8 and RNA polymerase II (RNAPII) recruitment, RNAPII C-terminal domain phosphorylation and impaired activation of IEG transcription. A single alanine substitution at S986 reduced activation of an E26 (ETS)-responsive reporter by oncogenic Ras and mitogen-induced, Elk-1-dependent transcription, whereas activities of other transcriptional activators were unaffected. We also demonstrate that Elk-1 can associate with MED14 independently of MED23, which may facilitate phosphorylation of MED14 by ERK to impart a positive and selective impact on mitogen-responsive gene expression.