U2AF1 and chronic myelomonocytic leukemia: Genes encoding components of the splicing machinery that is involved in the splicing of introns during pre-mRNA maturation (mainly SF3B1, SRSF2, U2AF35/U2AF1, and ZRSR2) have been found frequently mutated in MDSs and CMML, and more rarely in MPNs and AML (Figure 1) [31,37-42].