The Prp19C subunits Cwc15 and Syf2 function in TREX occupancy and transcription elongation

The Prp19 complex (Prp19C) is conserved from yeast to human and functions in many different processes such as genome stability, splicing and transcription elongation. In the latter, Prp19C ensures TREX occupancy at transcribed genes. TREX in turn couples transcription to nuclear mRNA export by recruiting the mRNA exporter to transcribed genes and consequently to nascent mRNAs. Here, we assess the function of the nonessential Prp19C subunits Syf2 and Cwc15 in the interaction of Prp19C and TREX with the transcription machinery, Prp19C and TREX occupancy as well as transcription elongation. Whereas both proteins are important for Prp19C-TREX interaction, Syf2 is needed for full Prp19C occupancy, and Cwc15 is important for the interaction of Prp19C with RNA polymerase II and TREX occupancy. These partially overlapping functions are corroborated by a genetic interaction between{Delta} cwc15 and{Delta} syf2. Finally, Cwc15 also interacts genetically with the transcription elongation factor Dst1 and functions in transcription elongation. In summary, we uncover novel roles of the nonessential Prp19C components Syf2 and Cwc15 in Prp19Cs function in transcription elongation.