Role of Ser-Arg Proteins in the Regulation of RNA Processing

摘要

We have identified a complex SR-related matrix proteins of 16OkDa and 3OOkDa (SRm16O/3OO) that functions in splicing by promoting critical interactions between splicing factors bound to pre-mRNA, including snRNPs and SR family proteins (Blencowe et al., 1998; Eldridge et al., 1999). During the past year, we have investigated the functions of the SRm16O/3OO subunits. Surprisingly, specific depletion of SRm3O0 does not prevent the splicing of pre- mRNAs shown previously to require SRm160/300. Addition of recombinant SRm160 alone to SRm16O/30O-depleted reactions specifically activates splicing. The results indicate that SRm160 is the critical component of the SRm16O/3OO coactivator in the splicing of SRm16O/3OO dependent pre-mRNAs. This work paves the way for a more detailed investigation of interactions involving the SRm16O/ 3O0 splicing coactivator that are important for constitutive and regulated pre- mRNA splicing. The carboxyl terminal domain (CTD) of the largest subunit of RNA polymerase II is important for the efficient processing of pre-mRNA- it promotes 5' end capping, splicing and polyadenylation. In order to identify factors that communicate between the transcription and the RNA processing machineries, we have used affinity chromatography to purify proteins that specifically bind to the CTD.