Genome wide mapping of polyadenylation sites in proliferating and contact-inhibited cells and cells with knockdown of cleavage and polyadenylation factors

Purpose: Quiescence is a state of reversible cell cycle exit. Levels of polyadenylation factors decreases when proliferating cells become quiescent. The goals of this study are to determine the differential use of polyadenylation sites (changes in alternative polyadenylation) in quiescent vs. proliferating cells and also upon knockdown of polyadenylation factors. Methods: Two biological replicates of human dermal fibroblasts (12-1 and 12-3) were used for polyadeylation-site enriched RNA-seq on an Illumina HiSeq 2500 to compare quiescent vs. proliferating cells and polyadenylation factor knockdown vs. control cells. The reads were aligned to the human genome (hg19) uisng Tophat (2.0.14). The resulting bam files were used as an input to a python script provided by Gruber et al. (PMID: 27382025) to determine the counts for each polyadenylation site. Results: We observed a shift toward greater use of distal polyadenylation sites when the fibroblasts entered quiescence. We observed significant overlap between the genes that shift to greater distal site use with quiescence and CstF-64 or CPSF73 knockdown. Conclusions: The shift to greater distal site use with quiescence may reflect in part the reduced levels of cleavage and polyadenylation factors. Perform polyadenylation site-enriched RNA-Seq on: (1) two biological replicates of proliferating and quiescent (contact-inhibited) cells, and (2) two biological replicates of control and polyadenylation factor (CstF64, CPSF73 or CFIm25) knockdown cells.