Fig. 1

Different variants of APA. a In CR-APA the PAS is located within the coding region, which after polyadenylation can result in variations in the coding region at the C-terminal end, resulting in different protein isoforms. Protein isoforms could potentially have different functions within the cell to either lead to or hinder cell proliferation and tumor progression. b In UTR-APA, the PAS can be located within the 3′-UTR. Therefore, depending on the location of the PAS, the length of the 3′-UTR could be altered, thus generating new mRNA isoforms whilst not affecting the protein produced. However, the alteration of the 3′-UTR could affect accessibility to regulatory sites, such as for miRNA binding, which would affect expression level of the protein. While not generating new protein isoforms after UTR-APA, oncogenic proteins can be either over or under-expressed as a result of this process