pubmed.ncbi.nlm.nih.gov

The N-terminal side of the origin-binding domain of simian virus 40 large T antigen is involved in A/T untwisting - PubMed

The N-terminal side of the origin-binding domain of simian virus 40 large T antigen is involved in A/T untwisting

L Chen et al. J Virol. 1997 Nov.

Abstract

We investigated the role of the N-terminal side of simian virus 40 (SV40) large T antigen's origin-binding domain in the initiation of virus DNA replication by analyzing the biochemical activities of mutants containing single point substitutions or deletions in this region. Four mutants with substitutions at residues between 121 and 135 were partially defective in untwisting the A/T-rich track on the late side of the origin but were normal in melting the imperfect palindrome (IP) region on the early side. Deletion of the N-terminal 109 amino acids had no effect on either activity, whereas a longer deletion, up to residue 123, greatly reduced A/T untwisting but not IP melting. These results indicate that the region from residue 121 to 135 is important for A/T untwisting but not for IP melting and demonstrate that these activities are separable. Two point substitution mutants (126PS and 135PL) were characterized further by testing them for origin DNA binding, origin unwinding, oligomerization, and helicase activity. These two mutants were completely defective in origin (form U(R)) unwinding but normal in the other activities. Our results demonstrate that a failure to normally untwist the A/T track is correlated with a defect in origin unwinding. Further, they indicate that some mutants with substitutions in the region from residue 121 to 135 interact with origin DNA incorrectly, perhaps by failing to make appropriate contacts with the A/T-rich DNA.

PubMed Disclaimer

Cited by

Assembly of T-antigen double hexamers on the simian virus 40 core origin requires only a subset of the available binding sites.
Joo WS, Kim HY, Purviance JD, Sreekumar KR, Bullock PA. Joo WS, et al. Mol Cell Biol. 1998 May;18(5):2677-87. doi: 10.1128/MCB.18.5.2677. Mol Cell Biol. 1998. PMID: 9566887 Free PMC article.
Simian virus 40 DNA replication is dependent on an interaction between topoisomerase I and the C-terminal end of T antigen.
Khopde S, Simmons DT. Khopde S, et al. J Virol. 2008 Feb;82(3):1136-45. doi: 10.1128/JVI.01314-07. Epub 2007 Nov 14. J Virol. 2008. PMID: 18003733 Free PMC article.
Peptides containing cyclin/Cdk-nuclear localization signal motifs derived from viral initiator proteins bind to DNA when unphosphorylated.
Kim RJ, Moine S, Reese DK, Bullock PA. Kim RJ, et al. J Virol. 2002 Dec;76(23):11785-92. doi: 10.1128/jvi.76.23.11785-11792.2002. J Virol. 2002. PMID: 12414920 Free PMC article.
Simian virus 40 large T antigen can specifically unwind the central palindrome at the origin of DNA replication.
Wang W, Simmons DT. Wang W, et al. J Virol. 2009 Apr;83(7):3312-22. doi: 10.1128/JVI.01867-08. Epub 2009 Jan 14. J Virol. 2009. PMID: 19144705 Free PMC article.
Role of the hydrophilic channels of simian virus 40 T-antigen helicase in DNA replication.
Wang W, Manna D, Simmons DT. Wang W, et al. J Virol. 2007 May;81(9):4510-9. doi: 10.1128/JVI.00003-07. Epub 2007 Feb 14. J Virol. 2007. PMID: 17301125 Free PMC article.

References

1. EMBO J. 1992 Feb;11(2):769-76 - PubMed
1. J Biol Chem. 1992 Apr 15;267(11):7284-94 - PubMed
1. J Virol. 1992 Sep;66(9):5248-55 - PubMed
1. J Virol. 1992 Sep;66(9):5443-52 - PubMed
1. J Virol. 1996 Jun;70(6):3887-93 - PubMed

The N-terminal side of the origin-binding domain of simian virus 40 large T antigen is involved in A/T untwisting - PubMed