Switch-like control of helicase processivity by single-stranded DNA binding protein

• Published in: eLife Vol. 10
• Main Authors: Stekas, Barbara, Yeo, Steve, Troitskaia, Alice, Honda, Masayoshi, Sho, Sei, Spies, Maria, Chemla, Yann R
• Format: Journal Article
• Language: English
• Published: England eLife Science Publications, Ltd 19.03.2021; eLife Sciences Publications Ltd; eLife Sciences Publications, Ltd
• Subjects: DNA; DNA binding proteins; DNA biosynthesis; DNA helicase; dna repair; Genomes; helicase; Hydrolysis; Molecular modelling; optical tweezers; Point mutation; Protein binding; Proteins; Replication protein A; single molecule; Single-stranded DNA; single-stranded DNA binding protein; Structural Biology and Molecular Biophysics; Unwinding; Xeroderma pigmentosum; XPD protein; single molecule; single-stranded DNA binding protein; optical tweezers; structural biology; dna repair; helicase; molecular biophysics
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.60515

Helicases utilize nucleotide triphosphate (NTP) hydrolysis to translocate along single-stranded nucleic acids (NA) and unwind the duplex. In the cell, helicases function in the context of other NA-associated proteins such as single-stranded DNA binding proteins. Such encounters regulate helicase function, although the underlying mechanisms remain largely unknown. Ferroplasma acidarmanus xeroderma pigmentosum group D (XPD) helicase serves as a model for understanding the molecular mechanisms of superfamily 2B helicases, and its activity is enhanced by the cognate single-stranded DNA binding protein replication protein A 2 (RPA2). Here, optical trap measurements of the unwinding activity of a single XPD helicase in the presence of RPA2 reveal a mechanism in which XPD interconverts between two states with different processivities and transient RPA2 interactions stabilize the more processive state, activating a latent ‘processivity switch’ in XPD. A point mutation at a regulatory DNA binding site on XPD similarly activates this switch. These findings provide new insights on mechanisms of helicase regulation by accessory proteins.