title: Mediator MED23 regulates basal transcription in vivo via an interaction with P-TEFb.
abstract: The Mediator is a multi-subunit complex that transduces regulatory information from transcription regulators to the RNA polymerase II apparatus. Growing evidence suggests that Mediator plays roles in multiple stages of eukaryotic transcription, including elongation. However, the detailed mechanism by which Mediator regulates elongation remains elusive. In this study, we demonstrate that Mediator MED23 subunit controls a basal level of transcription by recruiting elongation factor P-TEFb, via an interaction with its CDK9 subunit. The mRNA level of Egr1, a MED23-controlled model gene, is reduced 4-5 fold in Med23 (-/-)  ES cells under an unstimulated condition, but Med23-deficiency does not alter the occupancies of RNAP II, GTFs, Mediator complex, or activator ELK1 at the Egr1 promoter. Instead, Med23 depletion results in a significant decrease in P-TEFb and RNAP II (Ser2P) binding at the coding region, but no changes for several other elongation regulators, such as DSIF and NELF. ChIP-seq revealed that Med23-deficiency partially reduced the P-TEFb occupancy at a set of MED23-regulated gene promoters. Further, we demonstrate that MED23 interacts with CDK9 in vivo and in vitro. Collectively, these results provide the mechanistic insight into how Mediator promotes RNAP II into transcription elongation.
authors: State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors: Wei
authors: W
authors: Wang
authors: Xiao
authors: X
authors: Yao
authors: Yan
authors: Y
authors: Huang
authors: Xiangming
authors: X
authors: Hu
authors: Runzhong
authors: R
authors: Liu
authors: Dongming
authors: D
authors: Hou
authors: Ruichuan
authors: R
authors: Chen
authors: Gang
authors: G
authors: Wang
mesh_terms: D000818:Animals; D002460:Cell Line; D042863:Cyclin-Dependent Kinase 9 / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D056892:Mediator Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D021122:Protein Subunits; D012319:RNA Polymerase II / Q000378:metabolism; D061805:Transcription Elongation, Genetic; D014158:Transcription, Genetic; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism
chemical_list: D051766:Early Growth Response Protein 1; C492159:MED23 protein, human; D056892:Mediator Complex; D021122:Protein Subunits; D050807:ets-Domain Protein Elk-1; D011494:Protein Kinases; C060137:carboxy-terminal domain kinase; D042925:Positive Transcriptional Elongation Factor B; D042863:Cyclin-Dependent Kinase 9; D012319:RNA Polymerase II
keywords: Egr1; Mediator MED23; P-TEFb; basal transcription; elongation