DNA-binding component of the Fanconi anemia (FA) core complex. Required for the normal activation of the FA pathway, leading to monoubiquitination of the FANCI-FANCD2 complex in response to DNA damage, cellular resistance to DNA cross-linking drugs, and prevention of chromosomal breakage (PubMed:20347428, PubMed:20347429). In complex with CENPS (MHF heterodimer), crucial cofactor for FANCM in both binding and ATP-dependent remodeling of DNA. Stabilizes FANCM. In complex with CENPS and FANCM (but not other FANC proteins), rapidly recruited to blocked forks and promotes gene conversion at blocked replication forks (PubMed:20347428, PubMed:20347429). In complex with CENPS, CENPT and CENPW (CENP-T-W-S-X heterotetramer), involved in the formation of a functional kinetochore outer plate, which is essential for kinetochore-microtubule attachment and faithful mitotic progression (PubMed:19620631). As a component of MHF and CENP-T-W-S-X complexes, binds DNA and bends it to form a nucleosome-like structure (PubMed:20347428, PubMed:20347429). DNA-binding function is fulfilled in the presence of CENPS, with the following preference for DNA substates: Holliday junction > double-stranded > splay arm > single-stranded. Does not bind DNA on its own (PubMed:20347429). Heterodimer with CENPX, sometimes called MHF; this interaction stabilizes both partners (PubMed:19620631, PubMed:20347428, PubMed:20347429, PubMed:24522885). MHF heterodimers can assemble to form tetrameric structures (PubMed:22304917). MHF also coassemble with CENPT-CENPW heterodimers at centromeres to form the tetrameric CENP-T-W-S-X complex (PubMed:22304917, PubMed:24522885). Forms a discrete complex with FANCM and CENPX, called FANCM-MHF; this interaction, probably mediated by direct binding between CENPS and FANCM, leads to synergistic activation of double-stranded DNA binding and strongly stimulates FANCM-mediated DNA remodeling (PubMed:20347428, PubMed:20347429). Recruited by FANCM to the Fanconi anemia (FA) core complex, which consists of CENPS, CENPX, FANCA, FANCB, FANCC, FANCE, FANCF, FANCG, FANCL, FANCM, FAAP24 and FAAP100. The FA core complex associates with Bloom syndrome (BLM) complex, which consists of at least BLM, DNA topoisomerase 3-alpha (TOP3A), RMI1/BLAP75, RPA1/RPA70 and RPA2/RPA32. The super complex between FA and BLM is called BRAFT (PubMed:20347428, PubMed:20347429). Assembly of CENPS and CENPX and its partner subunits CENPT and CENPW at centromeres occurs through a dynamic exchange mechanism. Although exchange is continuous in the cell cycle, de novo assembly starts principally during mid-late S phase and is complete by G2. CENPX being less stably bound at the kinetochore than CENPS. Expression varies across the cell cycle, with highest levels in S phase (at protein level). No statistically significant changes at the transcript level. Belongs to the CENP-X/MHF2 family.