Fig 1: CELF2 Competes with CFIm25 and CstF64 to Regulate APA of Its Own 3′ UTR(A and B) In vitro UV crosslinking analysis of indicated amount of recombinant CstF64 (A) or CFIm25 (B) protein bound to radiolabeled PAS2 oligonucleotide in the absence or presence of increasing amounts of recombinant CELF2 (left) or hnRNPL (right). hnRNPL protein crosslinked to M1 oligonucleotide (Thompson et al., 2018) is shown as a positive control for hnRNPL binding to RNA. The lane with hnRNP L alone was run on a different gel. (C) Left, schematic of reporter constructs and right, 3ʹ RACE analysis of mutant constructs upon transfection in HeLa cells with (+) or without (−) cotransfected CELF2 cDNA. Asterisk marks the product resulting from use of SV40 PAS. Red boxes indicate location of mutations that disrupt binding of CstF64, CFIm25, and CELF2, as indicated in the text. swPAS3 lacks all sequences around the native PAS3 (shown as a dark gray box), such that the vector-encoded non-PMA responsive SV40 polyA is the only other PAS present.See also Figure S4.