MBE Advance Access originally published online on March 10, 2006
Molecular Biology and Evolution 2006 23(6):1097-1100; doi:10.1093/molbev/msj122
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Letter |
Two Families of Rep-Like Genes That Probably Originated by Interspecies Recombination Are Represented in Viral, Plasmid, Bacterial, and Parasitic Protozoan Genomes
* School of Botany and Zoology, The Australian National University, Canberra, Australia; Food Science, University of Wisconsin at Madison; The Australian Centre for International and Tropical Health and Nutrition, Queensland Institute of Medical Research, Brisbane, Queensland, Australia; and Department of Microbiology, Russian State Medical University, Moscow, Russia
E-mail: mark.gibbs{at}anu.edu.au.
Two families of genes related to, and including, rolling circle replication initiator protein (Rep) genes were defined by sequence similarity and by evidence of intergene family recombination. The Rep genes of circoviruses were the best characterized members of the "RecRep1 family." Other members of the RecRep1 family were Rep-like genes found in the genomes of the Canarypox virus, Entamoeba histolytica, and Giardia duodenalis and in a plasmid, p4M, from the Gram-positive bacterium, Bifidobacterium pseudocatenulatum. The "RecRep2 family" comprised some previously identified Rep-like genes from plasmids of phytoplasmas and similar Rep-like genes from the genomes of Lactobacillus acidophilus, Lactococcus lactis, and Phytoplasma asteris. Both RecRep1 and RecRep2 proteins have a nucleotide-binding domain significantly similar to the helicases (2C proteins) of picorna-like viruses. On the N-terminal side of the nucleotide binding domain, RecRep1 proteins have a domain significantly similar to one found in nanovirus Reps, whereas RecRep2 proteins have a domain significantly similar to one in the Reps of pLS1 plasmids. We speculate that RecRep genes have been transferred from viruses or plasmids to parasitic protozoan and bacterial genomes and that Rep proteins were themselves involved in the original recombination events that generated the ancestral RecRep genes.
Key Words: interspecies recombination • gene family • circovirus • RecRep1 • pLS1 plasmid • parasitic protozoan