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Analysis of a human immunodeficiency virus type 1 isolate carrying a truncated transmembrane glycoprotein
Abstract:
We have recently reported the isolation of a human immunodeficiency virus type 1 (HIV-1), KB-1gp32 carrying a shorter size (32 kDa) of transmembrane glycoprotein (TMP) from TALL-1 cells persistently infected with KB-1gp41 virus strain (Shimizu et al., 1990a). Endoglycosidase treatments showed that the different size of the TMP between the two strains was due to a truncation of 9 kDa of polypeptide in the KB-1gp32 TMP coding region. Sequence analysis revealed the substitution of a CAG codon to a TAG stop codon just downstream of the putative membrane-spanning domain of the TMP of KB-1gp32. This resulted in a truncation of some 133 amino acids of the cytoplasmic domain of TMP. The data indicate that a premature stop codon in KB-1gp32 has been introduced during adaption of the parental virus to TALL-1 cells. We have constructed two chimeric clones between the env region of a clone pKB-1, derived from KB-1gp32, and an infectious molecular clone pNL-432. We have also constructed a site-directed mutant of pNL-432 carrying a premature stop codon at the same position as the env stop codon of pKB-1. Among the three clones carrying a premature stop codon in env, only one chimeric clone was infectious to TALL-1 but not MT-2 cells. This clone contained the entire tat, rev, vpu, and env genes of pKB-1. The pNL-432 mutant was not infectious. The results suggest that some sequences of pKB-1 might compensate for the truncation of the TMP during replication in TALL-1 cells.
Insights
A premature stop codon in human immunodeficiency virus type 1 (HIV-1) KB-1gp32 resulted in a truncated transmembrane glycoprotein (TMP). This truncation, caused by adaptation to TALL-1 cells, impacted viral replication and cell tropism.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Human immunodeficiency virus type 1 (HIV-1) KB-1gp32 exhibits a shorter transmembrane glycoprotein (TMP) compared to the KB-1gp41 strain.
- This size difference in TMP is attributed to a 9 kDa polypeptide truncation in the KB-1gp32 TMP coding region.
Purpose of the Study:
- To investigate the molecular basis for the truncated TMP in HIV-1 KB-1gp32.
- To determine the functional consequences of TMP truncation on viral replication and cell tropism.
Main Methods:
- Endoglycosidase treatments to analyze TMP size.
- Sequence analysis to identify genetic alterations in the TMP coding region.
- Construction of chimeric HIV-1 env genes and site-directed mutants.
- Infectivity assays in TALL-1 and MT-2 cells.
Main Results:
- Sequence analysis revealed a premature TAG stop codon in KB-1gp32 TMP, truncating 133 amino acids from the cytoplasmic domain.
- A chimeric clone containing pKB-1 env genes, including tat, rev, vpu, and env, was infectious to TALL-1 cells but not MT-2 cells.
- A site-directed mutant of pNL-432 with the premature stop codon was not infectious.
Conclusions:
- The premature stop codon in KB-1gp32 likely arose during adaptation to TALL-1 cells.
- Specific sequences within the pKB-1 genome may compensate for TMP truncation, influencing viral replication and tropism in TALL-1 cells.