SV40 T antigen helicase domain regions responsible for oligomerisation regulate Okazaki fragment synthesis initiation
Onwubiko, Nichodemus O. Scheffel, Felicia Tessmer, Ingrid Nasheuer, Heinz-Peter
Onwubiko, Nichodemus O.
Scheffel, Felicia
Tessmer, Ingrid
Nasheuer, Heinz-Peter
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Publication Date
2022-01-24
Keywords
*Antigens, Viral, Tumor/genetics/metabolism, DNA/genetics, Replication Protein A/genetics/metabolism, *Simian virus 40/genetics/metabolism, *DNA polymerase ¿-primase (Pol ¿), *Okazaki fragment synthesis, *SV40 large T antigen, *eukaryotic DNA replication, *initiation reaction, *replication protein A (RPA)
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Article
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Onwubiko, Nichodemus O., Scheffel, Felicia, Tessmer, Ingrid, & Nasheuer, Heinz Peter. (2022). SV40 T antigen helicase domain regions responsible for oligomerisation regulate Okazaki fragment synthesis initiation. FEBS Open Bio, 12(3), 649-663. doi:https://doi.org/10.1002/2211-5463.13373
Abstract
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 ¿-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.
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Wiley Open Access and Federation of European Biochemical Societies
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Attribution 4.0 International (CC BY 4.0)