Mpp6 regulates the interaction of Nrd1 with nuclear exosome and the C-terminal domain of RNA polymerase II

Abstract

The yeast saccharomyces cerevisiae Nrd1 interacts with C-terminal domain (CTD) of RNA polymerase II (RNApII) through its CTD-interacting domain (CID) and also associates with the nuclear exosome, thereby acting as both a transcription termination and RNA processing factor. It was recently reported that the Nrd1 CID couples RNApII termination and subsequent RNA processing by recruiting the nuclear exosome to the Nrd1 complex. However, what bridges the Nrd1 CID to the nuclear exosome was not clear. In this study using yeast two hybrid assay, I show two nuclear exosome cofactors, Mpp6 and Trf4 directly and competitively interact with the Nrd1 CID, and regulate the interaction of Nrd1 with RNApII and/or the exosome. Various analyses indicated that Mpp6 promotes the processing of Nrd1-terminated transcripts by Dis3, while Trf4 leads to Rrp6-dependent processing. It implies that Mpp6 and Trf4 may play pivotal roles in choosing a particular RNA processing route within the exosome by guiding the Nrd1-terminated transcripts to their preferred exonucleases.