Abstract P179: miR-214 Reduces Termination Efficiencies of Alternative Transcriptional Termination Sites

Abstract

Alternative polyadenylation signals are genomic sites where transcription can be terminated, resulting in the production of transcripts often with shorter 3’ sequences. While it is clear that alternative transcriptional termination impacts the action of microRNAs, it is not known whether the reverse is true. We identified miR-214, a microRNA upregulated in the kidneys of Dahl salt-sensitive rats, as a potent regulator of the use of alternative transcriptional termination sites. miR-214 targeted human and rat cleavage and polyadenylation specific factor 4 (CPSF4), a component of the CPSF complex that plays a key role in transcriptional termination. miR-214 reduced the termination efficiency of the classic alternative termination site in human cyclin D1 gene from 66% to 47% (P<0.05). Of genes in HeLa cells that showed large abundance shifts between transcript isoforms with shorter and longer 3’ sequences in response to miR-214, a significantly greater portion (69%, 35 of 51 pairs ) shifted to longer isoforms (P<0.01). Interestingly, an alternative polyadenylation site was predicted and confirmed in the genomic region upstream of the sequence encoding miR-214 itself. The use of the alternative polyadenylation site correlated with decreased miR-214 abundance in rat tissues in vivo. The termination efficiency of the alternative termination site was reduced from 60% to 32% (P<0.001) by miR-214. The termination efficiency was not reduced by miR-214 if CPSF4 had been knocked down by siRNA. These data indicate that miR-214 can relieve alternative polyadenylation-dependent transcriptional termination signals including one that influences its own expression.