Middle region of FancM interacts with M hf and R mi1 in silkworms, a species lacking the F anconi anaemia ( FA ) core complex

The F anconi anaemia ( FA ) pathway is responsible for interstrand crosslink ( ICL ) repair. Among the FA core complex components, FANCM is believed to act as a damage sensor for the ICL ‐blocked replication fork and also as a molecular platform for FA core complex assembly and interaction with B loom's syndrome ( BS ) complex that is thought to play an important role in the processing of DNA structures such as stalled replication forks. In the present study, we found that in silkworms, B ombyx mori , a species lacking the major FA core complex components ( FANCA , B , C , E , F , and G ), FancM is required for FancD2 monoubiquitination and cell proliferation in the presence of mitomycin C ( MMC) . Silkworm FancM ( BmFancM ) was phosphorylated in the middle regions, and the modification was associated with its subcellular localization. In addition, BmFancM interacted with M hf1, a histone‐fold protein, and R mi1, a subunit of the BS complex, in the different regions. The interaction region containing at least these two protein‐binding domains played an essential role in FancM ‐dependent resistance to MMC . Our results suggest that BmFancM also acts as a platform for recruitment of both the FA protein and the BS protein, although the silkworm genome seems to lose FAAP24 , a FancM ‐binding partner protein in mammals.