Study of the HIV-2 Env cytoplasmic tail variability and its impact on Tat, Rev and Nef.
BACKGROUND
The HIV-2 env's 3' end encodes the cytoplasmic tail (CT) of the Env protein. This genomic region also encodes the rev, Tat and Nef protein in overlapping reading frames. We studied the variability in the CT coding region in 46 clinical specimens and in 2 reference strains by sequencing and by culturing. The aims were to analyse the variability of Env CT and the evolution of proteins expressed from overlapping coding sequences.


RESULTS
A 70% reduction of the length of the CT region affected the HIV-2 ROD and EHO strains in vitro due to a premature stop codon in the env gene. In clinical samples this wasn't observed, but the CT length varied due to insertions and deletions. We noted 3 conserved and 3 variable regions in the CT. The conserved regions were those containing residues involved in Env endocytosis, the potential HIV-2 CT region implicated in the NF-kB activation and the potential end of the lentiviral lytic peptide one. The variable regions were the potential HIV-2 Kennedy region, the potential lentiviral lytic peptide two and the beginning of the potential lentiviral lytic peptide one. A very hydrophobic region was coded downstream of the premature stop codon observed in vitro, suggesting a membrane spanning region. Interestingly, the nucleotides that are responsible for the variability of the CT don't impact rev and Nef. However, in the Kennedy-like coding region variability resulted only from nucleotide changes that impacted Env and Tat together.


CONCLUSIONS
The HIV-2 Env, Tat and Rev C-terminal part are subject to major length variations in both clinical samples and cultured strains. The HIV-2 Env CT contains variable and conserved regions. These regions don't affect the rev and Nef amino acids composition which evolves independently. In contrast, Tat co-evolves with the Env CT.
Institut de recherche expérimentale et clinique, Université catholique de Louvain, Brussels, Belgium.
Nordine
N
Bakouche
Anne-Thérèse
AT
Vandenbroucke
Patrick
P
Goubau
Jean
J
Ruelle
D000328:Adult; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002648:Child; D005260:Female; D015686:Gene Products, env / Q000235:genetics*; D015693:Gene Products, nef / Q000235:genetics*; D015694:Gene Products, rev / Q000235:genetics*; D015696:Gene Products, tat / Q000235:genetics*; D014644:Genetic Variation; D057809:HEK293 Cells; D015658:HIV Infections / Q000821:virology; D015498:HIV-2 / Q000145:classification / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D011533:Proviruses / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D055815:Young Adult
D015686:Gene Products, env; D015693:Gene Products, nef; D015694:Gene Products, rev; D015696:Gene Products, tat