SF3B1 and cancer: To assess the importance of such 3′ SS in cell function or diseases, we examined the enrichment level of GGG between the −15 and −3 positions, together with pyrimidine- and the other purine-triplets, in the aberrantly used 3′ SS of human cancer samples containing mutations of 3′ SS factors, specifically SF3B1 or U2AF35 (Brooks et al., 2014; Darman et al., 2015; Alsafadi et al., 2016; Agrawal et al., 2017; Kesarwani et al., 2017).