title: Nonrandom distribution of cryptic repeating triplets of purines and pyrimidines (RNY)(n) in gp120 of HIV Type1.
abstract: We have analyzed purine (R) and pyrimidine (Y) codon patterns in variable and constant regions of HIV-1 gp120 in seven patients infected with different HIV-1 subtypes and naive to antiretroviral therapy. We have calculated the relative frequency of each in-frame codon RNY, YNR, RNR, and YNY (N=any nucleotide) in variable and constant regions of gp120, in the sequence within indels and at indels' flanking sites. Our data show that hypervariable regions V1, V2, V4, and V5 are characterized by the presence of long stretches of RNY codons constituting the majority of the sequence portion within insertions/deletions. In full-length gp120 and within inserted/deleted fragments the number of AVT (V=A, C, G) codons did not exceed 50% of the total RNY codons. RNY strings in variable regions spanned up to 21 codons and were always in frame. In contrast, RNY strings in constant regions were mostly out of frame and their length was limited to five codons. The frequency of the codon RNY was found to be significantly higher in variable regions (p<0.0001; t-test), within indels, and at indels' flanking sites (p<0.0001; χ(2) test). Analysis of the distribution of RNY strings equal to or longer than five codons in the full genome of HXB2 also shows that these sequences are mostly out of frame, unless they contain a potential N-glycosylation site or an asparagine. These data suggest that cryptic repeats of RNY may play a role in the genesis of multiple base insertions and deletions in hypervariable regions of gp120.
authors: Laboratory of AIDS Immunopathogenesis, Division of Immunology and Allergy, Department of Medicine, CHUV, Lausanne, Switzerland.
authors: Elisa
authors: E
authors: De Crignis
authors: Silvia
authors: S
authors: Guglietta
authors: Brian T
authors: BT
authors: Foley
authors: Matteo
authors: M
authors: Negroni
authors: Antonio Fabio
authors: AF
authors: Di Narzo
authors: Vreneli
authors: V
authors: Waelti Da Costa
authors: Matthias
authors: M
authors: Cavassini
authors: Pierre-Alexandre
authors: PA
authors: Bart
authors: Giuseppe
authors: G
authors: Pantaleo
authors: Cecilia
authors: C
authors: Graziosi
mesh_terms: D003062:Codon; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D014644:Genetic Variation; D015699:HIV Envelope Protein gp120 / Q000235:genetics*; D006679:HIV Seropositivity / Q000235:genetics* / Q000821:virology; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010802:Phylogeny; D011687:Purines / Q000378:metabolism; D011743:Pyrimidines / Q000378:metabolism; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: D003062:Codon; D004279:DNA, Viral; D015699:HIV Envelope Protein gp120; D011687:Purines; D011743:Pyrimidines