The consequences of RPB1-CTD truncation for human transcriptome dynamics

The carboxy-terminal domain of RPB1 subunit of RNA Polymerase II (CTD) plays an essential function in the regulation of gene expression and the coordination of co-transcriptional processes. CTD consists of hepta-amino acid repeats varying in number from 52 in humans to 26 in yeast and its length is crucial for spatial organization of transcriptional machinery in the nucleus. We found that the proximal half of the CTD is sufficient to support RNA metabolism and co-transcriptional processing in steady state conditions in human cells. Signal induced transcription, however, is severely impaired upon CTD shortening. Our data suggest that CTD length increased in evolution to allow for spatio-temporal control of gene expression patterns at least in part by facilitating enhancer function. Effects of RPB1-CTD shortening (from 52 to 25 heptad repeats) on transcription in human cells without treatment and in cells tratead with 12-O-Tetradecanoylphorbol-13-acetate (TPA) or DMSO (solvent) for 15 min or 30 min.