SV40 T antigen helicase domain regions responsible for oligomerisation regulate Okazaki fragment synthesis initiation.

Autor: Onwubiko NO; Biochemistry, School of Biological and Chemical Sciences, Biomedical Sciences Building, NUI Galway, Galway, Ireland., Scheffel F; Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany., Tessmer I; Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany., Nasheuer HP; Biochemistry, School of Biological and Chemical Sciences, Biomedical Sciences Building, NUI Galway, Galway, Ireland.
Jazyk: angličtina
Zdroj: FEBS open bio [FEBS Open Bio] 2022 Mar; Vol. 12 (3), pp. 649-663. Date of Electronic Publication: 2022 Feb 07.
DOI: 10.1002/2211-5463.13373
Abstrakt: The initiation of Okazaki fragment synthesis during cellular DNA replication is a crucial step for lagging strand synthesis, which is carried out by the primase function of DNA polymerase α-primase (Pol-prim). Since cellular replication protein A (RPA) prevents primase from starting RNA synthesis on single-stranded DNA (ssDNA), primase requires auxiliary factors, such as the simian virus 40 (SV40) T antigen (Tag), for the initiation reaction on RPA-bound ssDNA. Here, we investigated the ability of Tag variants and Tag protein complexes to bind to ssDNA and their resulting effects on the stimulation of Pol-prim on free and RPA-bound ssDNA. Atomic force microscopy imaging showed that while Tag 131-627 (V350E/P417D) and Tag 131-627 (L286D/R567E) (abbreviated as M1 and M2, respectively) could bind to ssDNA as monomers, these monomeric Tags could come together and bind to ssDNA as dimers as well. In a model assay for the initiation of Okazaki fragment synthesis, full-length Tag SV40 Tag 1-708 and monomeric M2 stimulated DNA synthesis of Pol-prim on ssDNA and on RPA-bound ssDNA. In contrast, neither monomeric M1 nor M1-M2 dimers could stimulate Pol-prim, on ssDNA or on RPA-bound ssDNA. Overall, we show that a lack of stimulatory activity of monomeric M1 and M1-M2 dimers suggests that residues V350 and P417 are not only important for interactions between Tag molecules but also for protein-protein interactions within Okazaki fragment initiation complexes. Thus, we highlight that mutations in M1 are dominant negative with regard to Okazaki fragment initiation.
(© 2022 The Authors. FEBS Open Bio published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)
Databáze: MEDLINE
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