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KMID : 1161520160200050282
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Animal Cells and Systems
2016 Volume.20 No. 5 p.282 ~ p.288
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β-Actin regulates interleukin 6-induced p21 transcription by interacting with the Rpb5 and Rpb7 subunits of RNA polymerase II
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Tian Xiujuan
Qi Wenjing
Chen Hongyu
Zeng Xianlu
Han Liping
Mi Donghui
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Abstract
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In pre-initiation complexes, RNA helicase A interacts with β-actin and acts as a bridging factor linking nuclear actin with RNA polymerase II (Pol II). In addition, β-actin participates in Pol II-dependent transcription elongation by interacting with the positive transcription elongation factor Cdk9. However, many relationships between β-actin and Pol II remain to be identified. In an interleukin 6 (IL-6)-induced p21 expression model, we demonstrated that β-actin knockdown reduced p21 expression. Immunofluorescence analysis showed that the colocalization of β-actin and Pol II increased significantly in cells treated with IL-6. It is known that the Rpb5, Rpb6 and Rpb7 subunits are located at the surface of the enzyme. We next constructed recombinant pcDNA-HA-Rpb5, pcDNA-HA-Rpb6 and pcDNA-HA-Rpb7 plasmids and expressed the three polymerase II subunits in HepG2 cells. We found that β-actin could be immunoprecipitated with HA-Rpb5 and HA-Rpb7. A Glutathione-S-transferase pull-down assay revealed that β-actin was associated with Rpb5 and Rpb7 in vitro. Furthermore, overexpression of Rpb5 and Rpb7 in cells reduced p21 expression significantly, suggesting that Rpb5 and Rpb7 competitively interact with β-actin. This study shows that β-actin associates with Pol II subunits through direct protein-protein interactions and provides fundamental insight into Pol II transcriptional regulation.
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KEYWORD
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β-Actin, Rpb5, Rpb7, RNA polymerase II, transcriptional regulation
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