A dimeric Rep protein initiates replication of a linear archaeal virus genome: implications for the Rep mechanism and viral replication.
The Rudiviridae are a family of rod-shaped archaeal viruses with covalently closed, linear double-stranded DNA (dsDNA) genomes. Their replication mechanisms remain obscure, although parallels have been drawn to the Poxviridae and other large cytoplasmic eukaryotic viruses. Here we report that a protein encoded in the 34-kbp genome of the rudivirus SIRV1 is a member of the replication initiator (Rep) superfamily of proteins, which initiate rolling-circle replication (RCR) of diverse viruses and plasmids. We show that SIRV Rep nicks the viral hairpin terminus, forming a covalent adduct between an active-site tyrosine and the 5' end of the DNA, releasing a 3' DNA end as a primer for DNA synthesis. The enzyme can also catalyze the joining reaction that is necessary to reseal the DNA hairpin and terminate replication. The dimeric structure points to a simple mechanism through which two closely positioned active sites, each with a single tyrosine residue, work in tandem to catalyze DNA nicking and joining. We propose a novel mechanism for rudivirus DNA replication, incorporating the first known example of a Rep protein that is not linked to RCR. The implications for Rep protein function and viral replication are discussed.
Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, Fife KY16 9ST, United Kingdom.
Muse
M
Oke
Melina
M
Kerou
Huanting
H
Liu
Xu
X
Peng
Roger A
RA
Garrett
David
D
Prangishvili
James H
JH
Naismith
Malcolm F
MF
White
D004265:DNA Helicases / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism*; D008954:Models, Biological; D055503:Protein Multimerization; D023642:Rudiviridae; D015534:Trans-Activators / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*; D014779:Virus Replication
D004279:DNA, Viral; D015534:Trans-Activators; D014764:Viral Proteins; C045264:replication initiator protein; D004265:DNA Helicases