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A role for Elongin in Mediator recruitment at ATF6α regulated genes [RNA-Seq]

ABSTRACT: The bZIP transcription factor ATF6α is a master regulator of endoplasmic reticulum (ER) stress response genes. In this report, we identify the multifunctional RNA polymerase II transcription factor Elongin as a cofactor for ATF6α-dependent transcription activation. Biochemical studies reveal that Elongin functions at least in part by facilitating ATF6α-dependent loading of Mediator at the promoters and enhancers of ER stress response genes. Depletion of Elongin from cells leads to impaired transcription of ER stress response genes and to defects in the recruitment of Mediator and, in particular, its CDK8 kinase subunit. Taken together, these findings bring to light a new role for Elongin as a loading factor for Mediator during the ER stress response.

ORGANISM(S): Homo sapiens

PROVIDER: GSE172125 | GEO | 2021/09/01

REPOSITORIES: GEO

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Project description:Elongin is an RNA polymerase II (RNAPII)-associated factor that has been shown to stimulate transcriptional elongation in vitro. The Elongin complex is thought to be required for transcriptional induction in response to cellular stimuli and to ubiquitinate RNAPII in response to DNA damage. Yet the impact of the Elongin complex on transcription in vivo has not been well studied. Here, we performed comprehensive studies of the role of Elongin A, the largest subunit of the Elongin complex, on RNAPII transcription genome-wide. In an effort to explore regulatory roles for Elongin A, we performed IP-MS. We constructed a DLD1 cell line expressing Flag-tagged Elongin A at endogenous levels and performed anti-Flag immuno-purification of solubilized chromatin followed by analysis of binding partners by mass spectrometry in triplicates. We identified a large group of Elongin A-associated proteins. We confirmed a subset of possible interacting proteins by Co-IP and western blotting. Consistent with previous studies, we identified RNA Pol II subunits and proteins related to transcription elongation and RNA processing. Among the top hits, we identified nearly all subunits of the PAF1 complex, except for RTF1, which does not stably associate with mammalian PAF1. Concordantly, in our previous PAF1 proteomic study, Elongin A was also among the top hits. We also identified several subunits of the Integrator complex, a multi-subunit complex that has been shown to participate in enhancer RNA (eRNA) processing, a finding consistent with our conclusion that Elongin A localizes to potential enhancers. Collectively, our results suggest that Elongin A stably interacts with RNAPII and the transcription machinery on chromatin. Taken together, our studies suggest that Elongin A associates with the transcription machinery at actively transcribed genomic regions and may be involved in the release of paused RNAPII. However, Elongin A does not appear to be critical for maintaining transcription elongation rates in vivo.

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A role for Elongin in Mediator recruitment at ATF6α regulated genes [RNA-Seq]

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