The SMARCAL1 gene encodes a protein called HepA-related protein (HARP). This protein is required for transcriptional regulation, replication, repair, recombination, and covalent modification. It has helicase and ATPase activities that bind selectively to fork DNA relative to ssDNA or dsDNA and catalyze the rewinding of the stably unwound DNA. It also rewinds single-stranded DNA bubbles that are stably bound by replication protein A (RPA), and acts throughout the genome to reanneal stably unwound DNA, performing the opposite reaction of many enzymes, such as helicases and polymerases, which unwind DNA.
Defects in this protein have been associated with Schimke immuno-osseous dysplasia (SIOD) disorder, characterized by spondyloepiphyseal dysplasia, renal dysfunction and T-cell immunodeficiency.