Translation of hSNM1 is mediated by an internal ribosome entry site that upregulates expression during mitosis

SNM1 is involved in the repair of DNA interstrand cross-links (ICLs) in Saccharomyces cerevisiae and possibly in human cells, although relatively little is known about its biochemical function. The hSNM1 contains a long 5′ untranslated region (5′UTR) predicted to fold into a complex secondary structure, and which contains numerous short open reading frames (ORFs). We show here using bicistronic constructs that human SNM1 mRNA contains an internal ribosome entry site (IRES) that generally suppresses translation, except during mitosis where translation is upregulated. These results suggest that hSNM1 may have a mitotic function possibly involved in response to DNA interstrand cross-linking agents.