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Abl-dependent tyrosine phosphorylation of the RNAPII-CTD increases binding affinity with the active miRNA Microprocessor complex

Abstract

During RNA transcription, the Carboxyl-terminal domain (CTD) of RNA Polymerase II (RNAPII) is phosphorylated on its serine-5 (Ser-5) positions to trigger elongation and RNA 5'-capping. In addition, CTD is also phosphorylated on the serine-2 (Ser-2) positions, which stimulates RNA splicing and polyadenylation. In the case of DNA damage, Abl kinase is activated to induce Tyrosine-1 (Tyr-1) phosphorylation on CTD. However, the exact role and function of the Tyr-1 phosphorylation during DNA damage has yet to be understood. Here we discovered interactions between CTD peptides and various Drosha-associated proteins (DAPs) by a mass spectrometry pulldown experiment. By applying a number of in vitro binding assays, we identified that CTD interacts with DiGeorge syndrome critical region 8 (DGCR8), one of the key and necessary proteins in the Microprocessor complex responsible for miRNA biogenesis. We also showed that the CTD-DGCR8 interaction can be enhanced in the presence of active Abl kinase. Our results demonstrated a possible outcome followed by the CTD Tyr-1 phosphorylation during DNA damage, which is to recruit the active Microprocessor complex and initiate miRNA biogenesis

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