G-actin Participates in RNA Polymerase II-dependent Transcription Elongation by Recruiting Positive Transcription Elongation Factor b (P-TEFb)

Abstract

Actin is a key regulator of RNA polymerase (Pol) II-dependent transcription. Positive transcription elongation factor b (P-TEFb), a Cdk9/cyclin T1 heterodimer, has been reported to play a critical role in transcription elongation. However, the relationship between actin and P-TEFb is still not clear. In this study, actin was found to interact with Cdk9, a catalytic subunit of P-TEFb, in elongation complexes. Using immunofluorescence and immunoprecipitation assays, Cdk9 was found to bind to G-actin through the conserved Thr-186 in the T-loop. Overexpression and in vitro kinase assays showed that G-actin promotes P-TEFb-dependent phosphorylation of the Pol II C-terminal domain. An in vitro transcription experiment revealed that the interaction between G-actin and Cdk9 stimulated Pol II transcription elongation. ChIP and immobilized template assays indicated that actin recruited Cdk9 to a transcriptional template in vivo and in vitro. Using cytokine IL-6-inducible p21 gene expression system, we revealed that actin recruited Cdk9 to endogenous gene. Moreover, overexpression of actin and Cdk9 increased histone H3 acetylation and acetylized histone H3 binding to a transcriptional template through the interaction with histone acetyltransferase, p300. Taken together, our results suggested that actin participates in transcription elongation by recruiting Cdk9 for phosphorylation of the Pol II C-terminal domain, and the actin-Cdk9 interaction promotes chromatin remodeling.

The role of exportin 6 in cytoskeletal-mediated cell death and cell adhesion in human non-small-cell lung carcinoma cells following doxorubicin treatment

“…Nuclear actin is a key regulator of polymerase II-dependent transcription and is required for RNA polymerase I transcription [43][44]. Zhang et al showed the localization of FUrd in the nucleoli and connected this with active RNA polymerase I transcription [45].…”

β-Actin regulates interleukin 6-induced p21 transcription by interacting with the Rpb5 and Rpb7 subunits of RNA polymerase II

“…regulates the recruitment of Pol II (Tang et al 2009). Moreover, β-actin is also involved in transcription elongation by interacting with Cdk9 (Qi et al 2011). In this study, we treated HepG2 cells with IL-6 to induce gene expression and measured the expression of the targeting gene p21.…”

“…It has been reported that actin is a component of the chromatin remodeling complex, associates with hnRNP and acts as a platform for the recruitment of HAT or HDAC complexes to the active transcription unit (Dingova et al 2009). Previous studies in our lab have demonstrated that β-actin is required for the initiation and elongation steps of transcription (Tang et al 2009;Qi et al 2011). To evaluate whether β-actin regulates gene transcription directly, we built an IL-6-induced gene expression model in HepG2 cells and targeted p21 as an endogenous gene.…”

“…Additionally, several studies show that actin plays a key role in basal transcription by interacting with Pol I, II and III (Fomproix & Percipalle 2004;Hofmann et al 2004;Hu et al 2004;Ye et al 2008). Furthermore, recent studies in our lab demonstrate that β-actin plays a key role in the initiation and elongation steps of transcription by directly contacting the positive transcription elongation factor Cdk9 and RNA helicase A (RHA) (Tang et al 2009;Qi et al 2011). Pol II is known as a multi-subunit enzyme that synthesizes all mRNA precursors in eukaryotes.…”

Nuclear actin and myosins at a glance

“…Numerous Arps have been described in the nucleus (reviewed by Oma and Harata, 2011). Actin and Arps recruit chromatin remodeling complexes (Kukalev et al, 2005;Obrdlik et al, 2008;Qi et al, 2011;Blessing et al, 2004), and chromatin remodeling complexes associate with Arp4 and actin (Blessing et al, 2004). The nucleating activity of Arp2/3 is stimulated by Wiskott-Aldrich syndrome family proteins (WASPs), and both Arp2/3 and neural WASP (N-WASP) are found in the nucleus.…”