Human HELB is a processive motor protein that catalyzes RPA clearance from single-stranded DNA

Abstract

Significance Single-stranded DNA (ssDNA) is a key intermediate in many cellular DNA transactions, including DNA replication, repair, and recombination. Nascent ssDNA is rapidly bound by the Replication Protein A (RPA) complex, forming a nucleoprotein filament that both stabilizes ssDNA and mediates downstream processing events. Paradoxically, however, the very high affinity of RPA for ssDNA may block the recruitment of further factors. In this work, we show that RPA–ssDNA nucleoprotein filaments are specifically targeted by the human HELB helicase. Recruitment of HELB by RPA–ssDNA activates HELB translocation activity, leading to processive removal of upstream RPA complexes. This RPA clearance activity may underpin the diverse roles of HELB in replication and recombination.