Many biochemical studies demonstrate that MMS19 and other CIA complex components directly interact with diverse DNA metabolism enzymes, such as DNA helicases [XPD, FANCJ (Fanconi anemia complementation group J)], and RTEL1, DNA polymerase subunits (POLD1, POLA1, and POLE1), the nuclease DNA2, the DNA glycosylase NTHL1, and the DNA primase PRI2. This evidence concerns the gene RTEL1 and Fanconi anemia.