DDX5 (DEAD/H BOX 5), also known as HLR1 or G17P1, is an enzyme that in humans is encoded by the DDX5 gene. The p68 protein is a proliferation-associated nuclear antigen first identified through its highly specific cross-reaction with the simian virus 40 tumor antigen (Iggo et al., 1989). Subsequently, homology to eukaryotic translation initiation factor was found, and amino acid sequence blocks characteristic of a large superfamily of proteins with putative helicase activity were demonstrated. Brody et al. (1995) confirmed that this gene is located on chromosome 17 in the region of the BRCA1 gene at 17q21. By immunoprecipitation analysis, Caretti et al. (2006) found that p68, p72 (DDX17), and the noncoding RNA SRA (SRA1) associated with MYOD (MYOD1) in MYOD-transfected HeLa cells.