Modulation of diverse biological processes by CPSF, the master regulator of mRNA 3′ ends

Arabidopsis thaliana FY (WDR33) regulates FLC gene expression by resolving the COOLAIR R loop. (A) In A. thaliana, low temperature induces antisense transcription at the FLC locus, producing the antisense transcript COOLAIR. COOLAIR hybridizes to the template DNA strand, forming an R loop, which is recognized by the FCA/FY (WDR33) complex. (B) FY (WDR33), as part of CPSF, activates polyadenylation of COOLAIR at a weak PAS, and the R loop is then resolved. This ultimately leads to epigenetic silencing of the FLC gene.