Polyadenylation of mRNA precursors is frequently coupled to transcription by RNA polymerase II. Although this coupling is known to involve interactions with the C-terminal domain of the RNA polymerase II largest subunit, the possible role of other factors is not known. Here we show that a prototypical transcriptional activator, GAL4-VP16, stimulates transcription-coupled polyadenylation in vitro. In the absence of GAL4-VP16, specifically initiated transcripts accumulated but little polyadenylation was observed, while in its presence polyadenylation was strongly enhanced. We further show that this stimulation requires the transcription elongation-associated PAF complex (PAF1c), as PAF1c depletion blocked GAL4-VP16-stimulated polyadenylation. Furthermore, knockdown of PAF subunits by siRNA resulted in decreased 3′ cleavage, and nuclear export, of mRNA in vivo. Finally, we show that GAL4-VP16 interacts directly with PAF1c and recruits it to DNA templates. Our results indicate that a transcription activator can stimulate transcription-coupled 3′ processing and does so via interaction with PAF1c.
Highlights
► GAL4-VP16 stimulates transcription-coupled polyadenylation ► PAF1c is required for GAL-VP16-stimulated polyadenylation ► GAL4-VP16 interacts directly with PAF1c and recruits it to DNA templates
Present address: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1, Higashi, Tsukuba-shi, Ibaraki 305-8566, Japan