Fig. 1
From: Alternative polyadenylation: methods, mechanism, function, and role in cancer
Categories of APA. a Tandem 3’UTR-APA containing two or more poly(A) sites in the 3’untranslated region. b, c, d UR-APAs occurring upstream of the last exon, therefore termed as an upstream region APA. b Splicing APA (alternative terminal exon APA) possessing a proximal PAS in the last exon and resulting in internal exon skipping. c Intronic APA occurring in the introns. d Internal exon APA generating a 3’UTR-lacking isoform via the PAS usage in the upstream exon