DNA-binding component of the FA core complex involved in DNA damage repair and genome maintenance. Recruited to forks stalled by DNA interstrand cross-links; and required for cellular resistance to such lesions. Component of the heterotetrameric CENP-T-W-S-X complex that binds and supercoils DNA; and plays an important role in kinetochore assembly. Component of the APITD1/CENPS complex that is essential for the stable assembly of the outer kinetochore. Plays an important role in mitotic progression and chromosome segregation. {ECO:0000269|PubMed:19620631; ECO:0000269|Ref.5; ECO:0000269|Ref.6}.