The Function Of SON In RNA Pol Ⅱ Transcription Elongation

The transcription process of eukaryotic genes mainly includes the following five steps:pre-initiation complex assembling,initiation,pausing and release,elongation,and termination.Pausing and release is one of the most important rate-limiting steps in the process of eukaryotic gene transcription,and this step is mainly regulated by the positive transcription elongation factor b(P-TEFb);The transcription elongation process is accompanied by many coupling events,and it is also the main step in the synthesis of full-length RNA.Nuclear Speckles is a membraneless organelle composed of a large number of ribonucleoprotein particle clusters in the nucleus of mammalian cells.It can store,modify,and regulate RNA splicing factors,and regulate alternative splicing of RNA.According to the previous research,Nuclear Speckles is the place where active P-TEFb is formed,and can regulate the phosphorylation of Pol Ⅱ CTD,thereby regulating transcription,but the mechanism of Nuclear Speckles regulate transcription elongation and its specific regulatory factors is not clear.In this study,cell lines such as HeLa and F1C2 were used as experimental materials,and HMBA treatment was used as a model for activated transcription elongation.The improved nuclear fractionation protocol was used as the basic experimental method,combined with immunofluorescence,immunoprecipitation,quantitative Real-time PCR,RNA-seq and other experimental techniques further explore the regulation of transcription elongation by Nuclear Speckles.It was found that the deletion of Nuclear Speckles’s backbone protein SON would cause Pol Ⅱ to be unable to enter the elongation,and reduce the expression of a large number of genes.The absence of SON will cause Pafl to fall from Pol Ⅱ,and the transcription cannot be extended.The kinase DYRK1A in Nuclear Speckles has a regulatory effect on SON.The knock of DYRK1A will make SON unable to binding with Pol Ⅱ,and then affect the stability of Pafl and Pol Ⅱ binding and thus affect transcription.This study reveals the mechanism of Nuclear Speckles’s backbone protein SON in the regulation of transcription elongation,laying the foundation for further research on the relationship between Nuclear Speckles and transcription in the future.