Key component of the cytosolic iron-sulfur protein assembly (CIA) complex, a multiprotein complex that mediates the incorporation of iron-sulfur cluster into extramitochondrial Fe/S proteins (By similarity). As a CIA complex component, interacts specifically with CIAO2A or CIAO2B and MMS19 to assist different branches of iron-sulfur protein assembly, depending of its interactors. The complex CIAO1:CIAO2B:MMS19 binds to and facilitates the assembly of most cytosolic-nuclear Fe/S proteins. CIAO1:CIAO2A specifically matures ACO1 and stabilizes IREB2 (By similarity). Seems to specifically modulate the transactivation activity of WT1. As part of the mitotic spindle-associated MMXD complex it may play a role in chromosome segregation (By similarity). Component of the CIA complex. Interacts with CIAO2A and forms a complex with CIAO2B and MMS19; the interactions with CIAO2A and CIAO2B are mutually exclusive (PubMed:23891004) (By similarity). Interacts with CHD1L, ERCC2, IREB2 and POLD1 (By similarity). Component of the MMXD complex, which includes CIAO1, ERCC2, CIAO2B, MMS19 and SLC25A5. Interacts with WT1 (By similarity). Interacts with CIAO3 (By similarity). Interacts (via LYR motif) with HSC20. Belongs to the WD repeat CIA1 family.