MOV10 is a RNA helicase that is required for RNA-mediated gene silencing by RISC (RNA-induced silencing complex). Significantly, MOV10 is also required for the transcription and replication of the human hepatitis delta virus, also known as hepatitis D. Belonging to the same family as MOV10, MOV10L1 (Moloney leukemia virus 10-like protein 1) is a 1211 amino acid RNA helicase that is expressed as three isoforms. Interestingly, isoform 1 is expressed exclusively in testis and isoform 2 is specifically expressed in cardiac myocytes. Isoform 1 may play a role in male germ cell development, whereas isoform 2 has been shown to potentiate phenylephrine-induced hypertrophic response in cardiomyocytes. Each isoform contains a RNA interaction motif, ATP binding site and helicase motif through which it carries out its function.