Identification of sequences downstream of the primer binding site that are important for efficient replication of human immunodeficiency virus type 1.
Reverse transcription of retroviruses is initiated from an 18-nucleotide (nt) primer binding site (PBS), located within the 5' region of viral genomic RNA, to which the host cell-derived tRNA primer is annealed and also involves viral genomic sequences outside the PBS. We constructed proviral DNA clones of human immunodeficiency virus (HIV) that had selective deletions of either a 7-nt segment found immediately downstream of the PBS or an extended nontranslated 54-nt stretch located immediately downstream of the PBS and containing the aforementioned 7-nt segment. Synthesis of minus-strand strong-stop DNA was assessed with MT-4 cells infected with viruses derived from COS-7 cells that had been transfected with these various constructs. We found that similar levels of minus-strand strong-stop DNA as well as DNA produced after template switching were expressed in MT-4 cells infected with COS-7-derived wild-type viruses or with viruses that had the 7-nt segment deleted. In contrast, significantly lower levels of viral DNA were detected in MT-4 cells after infection with viruses that had deletions of the 54-nt stretch. Furthermore, the molecular clone containing the 7-nt deletion was able to replicate with wild-type kinetics, while that containing the 54-nt deletion displayed a significantly diminished capacity in this regard. Further deletion analysis showed that a 16-nt segment at the 3' end of this 54-nt segment was largely responsible for these effects. We also conducted studies to determine levels of viral mRNA in COS-7 cells that had been transfected with equivalent amounts of DNA derived from either a wild-type HIV construct or our various deletion mutants. In the case of transfections performed with the 7-nt deletion mutant and wild-type HIV DNA, high levels of viral mRNA transcripts were detected, which was not the case for the 54 nt-deletion mutant. However, these various mRNAs possessed similar stabilities, as shown through studies in which transcript formation was arrested by treatment of cells with actinomycin D. Thus, the 54-nt segment of 5' nontranslated RNA, located downstream of the PBS, is involved in efficient expression of each of viral DNA, mRNA, and infectious virus.
Li
X
X
McGill University AIDS Centre, Jewish General Hospital, and Department of Medicine, McGill University, Montreal, Quebec, Canada.
Liang
C
C
Quan
Y
Y
Chandok
R
R
Laughrea
M
M
Parniak
M A
MA
Kleiman
L
L
Wainberg
M A
MA
D001665:Binding Sites; D004279:DNA, Viral / Q000096:biosynthesis; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D009154:Mutation; D012367:RNA, Viral / Q000737:chemistry*; D014764:Viral Proteins / Q000096:biosynthesis; D014779:Virus Replication
D004279:DNA, Viral; D012367:RNA, Viral; D014764:Viral Proteins