title: Cap-binding protein complex links pre-mRNA capping to transcription elongation and alternative splicing through positive transcription elongation factor b (P-TEFb).
abstract: Promoter-proximal pausing of RNAPII coincides with the formation of the cap structure at the 5' end of pre-mRNA, which is bound by the cap-binding protein complex (CBC). Although the positive transcription elongation factor b (P-TEFb) stimulates the release of RNAPII from pausing and promotes transcription elongation and alternative splicing by phosphorylating the RNAPII C-terminal domain at Ser2 (S2-P RNAPII), it is unknown whether CBC facilitates these events. In this study, we report that CBC interacts with P-TEFb and transcriptionally engaged RNAPII and is globally required for optimal levels of S2-P RNAPII. Quantitative nascent RNA immunoprecipitation and ChIP experiments reveal that depletion of CBC attenuates HIV-1 Tat transactivation and impedes transcription elongation of investigated CBC-dependent endogenous genes by decreasing the levels of P-TEFb and S2-P RNAPII, leading to accumulation of RNAPII in the body of these genes. Finally, CBC is essential for the promotion of alternative splicing through facilitating P-TEFb, S2-P RNAPII, and splicing factor 2/alternative splicing factor occupancy at a splicing minigene. These findings disclose a vital role of CBC in connecting pre-mRNA capping to transcription elongation and alternative splicing via P-TEFb.
authors.affiliation: Research Programs Unit, Molecular Medicine, University of Helsinki, FIN-00014 Helsinki, Finland. tlenasi@yahoo.com
authors.forename: Tina
authors.initials: T
authors.lastname: Lenasi
authors.forename: B Matija
authors.initials: BM
authors.lastname: Peterlin
authors.forename: Matjaz
authors.initials: M
authors.lastname: Barboric
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics / Q000378:metabolism*; D039381:RNA Cap-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012322:RNA Precursors / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D039381:RNA Cap-Binding Proteins; D012322:RNA Precursors; D042925:Positive Transcriptional Elongation Factor B; D012319:RNA Polymerase II