GSE173374
THOC5 complexes with DDX5, DDX17 and CDK12 to regulate R loop structures and transcription elongation rate
THOC5, a member of the THO complex, is essential for the 3´processing of some inducible genes, the export of a subset of genes and stem cell self-renewal. Utilising nanopore mRNA-sequencing we show that when THOC5 is depleted 50-60% of mRNAs undergo altered 3´end cleavage. Further, THOC5 depletion leads to increased RNA Polymerase II (Pol II) presence at the start site, on the gene body and close to the 3'end. Moreover, THOC5 is recruited close to high density Pol II sites suggesting that THOC5 is involved in transcriptional elongation. Indeed, DRB/TTchem-seq that measures elongation rates in vivo revealed an accumulation of released Pol II near to TSS and a decrease of elongation rates in THOC5 depleted cells. Furthermore, THOC5 is more recruited to its target genes in cells expressing slow Pol II than those expressing fast Pol II. In cells expressing slow Pol II chromatin associated THOC5 interacts with CDK12 (a protein that modulates mRNA elongation rates), RNA helicases DDX5, DDX17, and THOC6. Importantly these interactions were not observed in cells expressing fast Pol II. 3' cleavage of 50% of THOC5 target genes is also regulated by CDK12 and THOC6. The CDK12/THOC5 interaction promotes CDK12 recruitment to R-loops in a THOC6-dependent manner. These data demonstrate that THOC5/THOC6 play a part in transcription elongation. Given the role of THOC5 in primitive cell survival its phosphorylation by agonists, oxidative stress and oncogenes the pathway we identified has relevance in the physiology and pathology of stem cells. Overall design: Transcriptome profiling of HEK293 cells characterized by Nanopore direct RNA-Seq. Recruitment profile of RNA PolII and THOC5 were examined by ChIP-Seq.