Ubiquitin ligase protein that mediates monoubiquitination of FANCD2, a key step in the DNA damage pathway. Also mediates monoubiquitination of FANCI. May stimulate the ubiquitin release from UBE2W. May be required for proper primordial germ cell proliferation in the embryonic stage, whereas it is probably not needed for spermatogonial proliferation after birth. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Belongs to the multisubunit FA complex composed of FANCA, FANCB, FANCC, FANCE, FANCF, FANCG, FANCL/PHF9 and FANCM (By similarity). In complex with FANCF, FANCA and FANCG, but not with FANCC, nor FANCE, interacts with HES1; this interaction may be essential for the stability and nuclear localization of FA core complex proteins. Interacts with FANCI (By similarity). Interacts with GGN. Interacts (via the RING-type zinc finger) with UBE2T and UBE2W. In the nucleus, colocalizes with UBE2W. The UBC-RWD region (URD) region mediates interaction with FANCI and FANCD2. The RING-type zinc finger domain is monoubiquitinated in the presence of UBE2T and UBE2W. Defects in Fancl are a cause of the gcd (germ cell deficient) mutant phenotype, which leads to reduced numbers of precursor germ cells and adult sterility, probably due to a reduced precursor germ cells proliferation. Despite its name, it does not contain a PHD-type zinc finger, but contains a RING-type zinc finger. Moreover, PHD-type zinc fingers do not have any ubiquitin ligase activity.