title: Variability and Signatures of RNase-H Amino Acid Domain and Central Polypurine Tract of HIV-1 B-Subtype from Drug-Naive Individuals.
abstract: BACKGROUND
  The conversion to HIV-1 single-stranded RNA into double-stranded DNA for nuclear integration is an essential viral step in replication: this process is mediated by Reverse-Transcriptase (RT) and by central polypurine tract (cPPT), a domain where the plus-strand synthesis requires viral primers produced by RNase-H cleavage. Recent studies highlighted the need of investigating the role of RNase-H in RT nucleoside-inhibitors-resistance, because specific mutation(s) could affect cPPT removal and RNase-H cleavage specificity. Thus, the variability of RNase-H and cPPT were studied.
  
  
  METHODS
  HIV-1 subtype-B sequences from 746 drug-naïve and 806 antiretroviral-(ARV)-treated patients were used and analysed.
  
  
  RESULTS
  In drug-naïve patients, among 54 RNase-H variable residues, 25 were mutated in >5% of patients, and 7 of them were highly variable (>25%), whilst in ARV-treated individuals, 53 RNase-H variable residues were observed, which 24 were mutated in >5% of patients and 6 of them were highly variable (>25%). Differently, a high conservation was observed in cPPT-area, with no statistically significant differences observed between the two datasets analysed. Nevertheless, in ARV-treated patients the variability of cPPT nucleotide at position 6 was found three times higher with respect to the drug-naïve dataset. The topology of the dendrogram has revealed the existence of a cluster (boostrap=0.98) grouping the A6GcPPT with V531I and S519N RNase-H signatures.
  
  
  CONCLUSIONS
  These signatures observed within cPPT and mostly in RNase-H, warrant advanced structural analysis to delineate their potential roles in the affinity/recognition of RT and the cleavage capacity of RNase-H. Exploring further the implications such changes may have on drug-resistance may be relevant.
authors.affiliation: BioMolecular Lab, Barletta (BT) 76121, Italy. salvatore.dimonte@gmail.com.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Dimonte
authors.forename: Muhammed
authors.initials: M
authors.lastname: Babakir-Mina
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D016000:Cluster Analysis; D014644:Genetic Variation; D005838:Genotype; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D054309:Ribonuclease H, Human Immunodeficiency Virus / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
chemical_list: D054309:Ribonuclease H, Human Immunodeficiency Virus