Mammalian SNM1 is required for genome stability

Area of Science:

• Genetics
• Molecular Biology
• DNA Repair Mechanisms

Background:

• The Saccharomyces cerevisiae SNM1 protein is involved in DNA interstrand crosslinks (ICLs) repair.
• Mammalian cells possess five SNM1 homologs, including Artemis, implicated in V(D)J recombination.
• Mouse models with Snm1 gene disruption exhibit sensitivity to mitomycin (MMC), a DNA interstrand crosslinker.

Purpose of the Study:

• To investigate the role of human SNM1 (hSNM1) and its homologs in ICL repair within human cells.
• To determine if hSNM1 functions independently of the Fanconi anemia (FA) pathway.

Main Methods:

• Utilized siRNA depletion in human fibroblasts to assess sensitivity to MMC.
• Measured cell survival and chromosome radial formation as endpoints for DNA damage sensitivity.
• Evaluated the epistatic relationship between hSNM1 and the FA pathway by depleting hSNM1 in FA cells.

Main Results:

• Depletion of hSNM1 significantly increased sensitivity to ICLs, indicated by reduced cell survival and increased chromosome radials.
• Depletion of Artemis did not affect sensitivity to ICLs.
• Combined disruption of Snm1 and Fancd2 in mice led to partial perinatal lethality, suggesting genetic interaction.
• Depleting hSNM1 in FA cells resulted in additive sensitivity to MMC.
• Mono-ubiquitination of FANCD2, a marker for FA pathway activation, was unaffected by hSNM1 depletion in normal cells.

Conclusions:

• hSNM1 plays a critical role in maintaining genome stability following ICL formation.
• hSNM1 represents a DNA repair pathway for ICLs that is distinct from the Fanconi anemia pathway.