WNK1 kinase and the termination factor PCF11 connect nuclear mRNA export with transcription

Transcription termination and mRNA export from the nucleus are closely regulated and coordinated processes. Nuclear export factors are recruited to actively transcribed genes through their interactions with protein complexes associated with transcription and co-transcriptional pre-mRNA processing. We determine a new role for the kinase WNK1 in the cross-talk of transcription termination and mRNA export. WNK1 was previously attributed a cytoplasmic role as a regulator of ion transport. However, we now show a nuclear function for this kinase where it is required for efficient mRNA export along with the transcription termination factor PCF11. Finally, we identify the phosphorylation of the CID domain of PCF11 as an important step for the release of the mRNA from the transcription locus, thus allowing efficient mRNA export to the cytoplasm. Overall design: RNA from cytoplasmic and nuclear extracts of HeLa cells was obtained, upon depletion of WNK1 kinase or from control cells. Upon pA selection, libraries were generated and sequenced. A duplicate experiment was performed for each sample.