Regulation of Human T-cell Leukemia Virus Type 1 Infection and Replication

Retroviruses have evolved complex mechanisms to regulate their cellular tropism and gene expression. It is generally accepted that productive infections proceed via interactions between viral envelope molecules and specific receptors on the host cell surface. Currently, there is no known receptor for HTLV-1, though a number of factors that enhance entry have been identified. In an effort to identify a cellular receptor or attachment factor for HTLV-1, we carried out a retroviral cDNA library screen, in which cDNA from permissive HeLa S3 cells was introduced into poorly susceptible NIH 3T3 cells. These cells were selected after infection with HTLV-1 envelope pseudotyped viral particles expressing a drug resistance gene. We isolated approximately 460 cDNAs, of which 20 were prioritized as potential candidates. These candidates are being tested to determine if they participate in viral entry. In addition to encoding the structural and enzymatic genes common to all retroviruses, HTLV-1 also encodes several accessory genes which contribute to viral replication and the maintenance of gene expression. A newly identified viral gene, HTLV-1 bZIP factor or <italic>hbz</italic>, has been shown to have pleiotropic effects as it functions differently in its protein and mRNA forms. In an effort to elucidate its role in HTLV-1 replication, we identified a novel function. Mutations that abrogated the <italic>hbz</italic> mRNA or disrupted a stem-loop in <italic>hbz</italic> mRNA, or mutations that eliminated or truncated the HBZ protein were introduced in a functional molecular clone of HTLV-1. The protein and stem-loop mutants had no effect on viral gene expression. However, the mutant that disrupted <italic>hbz</italic> mRNA expressed lower levels of <italic>tax</italic> mRNA, suggesting that <italic>hbz</italic> promotes <italic>tax</italic> expression. We found that this effect of <italic>hbz</italic> was indirect, as <italic>hbz</italic> represses another accessory gene, <italic>p30<super>II</super></italic>, which is known to sequester <italic>tax</italic> mRNA in the nucleus. These results provide new insights into the regulation of HTLV-1 infection, specifically viral entry and gene expression.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology and Biomedical Sciences: Molecular Genetics and Genomics

Year dc:date.available

2010

Author dc:creator

• Choudhary, Gunjan

Contributors dc:contributor

• Lee Ratner

• Biology
• Virology
• antisense
• HBZ
• HTLV-1
• p30
• Receptor
• Tax

Language dc:language

English (en)

DOI

https://doi.org/10.7936/K7ZS2TH8

OAI identifier oai:identifier

oai:openscholarship.wustl.edu:etd-1065