title: In vivo analysis of human T-cell leukemia virus type 1 reverse transcription accuracy.
abstract: Several studies have indicated that the genetic diversity of human T-cell leukemia virus type 1 (HTLV-1), a virus associated with adult T-cell leukemia, is significantly lower than that of other retroviruses, including that of human immunodeficiency virus type 1 (HIV-1). To test whether HTLV-1 variation is lower than other retroviruses, a tractable vector system has been developed to measure reverse transcription accuracy in one round of HTLV-1 replication. This system consists of a HTLV-1 vector that contains a cassette with the neomycin phosphotransferase (neo) gene, a bacterial origin of DNA replication, and the lacZalpha peptide gene region (the mutational target). The vector was replicated by trans-complementation with helper plasmids. The in vivo mutation rate for HTLV-1 was determined to be 7 x 10(-6) mutations per target base pair per replication cycle. The majority of the mutations identified were base substitution mutations, namely, G-to-A and C-to-T transitions, frameshift mutations, and deletion mutations. Mutation of the methionine residue in the conserved YMDD motif of the HTLV-1 reverse transcriptase to either alanine or valine (i.e., M188A or M188V) led to a factor of two increase in the rate of mutation, indicating the role of this motif in enzyme accuracy. The HTLV-1 in vivo mutation rate is comparable to that of bovine leukemia virus (BLV), another member of the HTLV/BLV genus of retroviruses, and is about fourfold lower than that of HIV-1. These observations indicate that while the mutation rate of HTLV-1 is significantly lower than HIV-1, this lower rate alone would not explain the low diversity in HTLV-1 isolates, supporting the hypothesis that HTLV-1 replicates primarily as a provirus during cellular DNA replication rather than as a virus via reverse transcription.
authors.affiliation: Department of Molecular Virology, Immunology, and Medical Genetics, The Arthur James Cancer Hospital and Solove Research Institute, Ohio State University Medical Center, Columbus 43210, USA. mansky.3@osu.edu
authors.forename: L M
authors.initials: LM
authors.lastname: Mansky
mesh_terms: D001483:Base Sequence; D004261:DNA Replication; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D012194:RNA-Directed DNA Polymerase / Q000235:genetics / Q000502:physiology; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D012194:RNA-Directed DNA Polymerase