Year: 2003
Type: dissertation
Abstract: Human immunodeficiency virus type 1 (HIV-1) is characterized by its extraordinary genetic diversity, which can be largely attributed to its error-prone DNA replication and high frequency of genetic recombination. The goal of this thesis is to gain a better understanding of the factors that modulate the frequency of HIV-1 recombination. Genetic recombination is suggested to occur much more frequently for HIV-1 than for murine leukemia virus (MLV). To more precisely compare their recombination frequencies, a series of single replication cycle assays were performed for both viruses using highly similar vectors and assay conditions. Results from two-vector recombination assays and reciprocal repeat deletion experiments confirmed the reported differences in intermolecular recombination. However, two different one-vector approaches, including direct repeat deletion assays and transduction-type recombination assays, indicated that template switching properties were very similar for HIV-1 and MLV. These results provide genetic evidence that coexpressed RNAs are less accessible to the recombination machinery during MLV replication than for HIV-1. Effects of altering genetic distance on the frequency of template switching were examined by using HIV-1 vectors containing degenerate repeated sequences, which provided a wide range of sequence variation similar to that of intra-subtype, inter-subtype, and inter-group HIV-1 strains. Results from these experiments indicated that the frequency of template switching decreased dramatically as sequence divergence between repeated sequences increased. For sequences that differed by about 25% or more, HIV-1 template switching directed by sequence homology appeared to be no more frequent than that which is homology independent. Retroviral transduction of cellular genes is frequently observed for oncoretroviruses. The transduction potential of HIV-1 was investigated with transduction-type recombination assays using vectors reminiscent of retroviral transduction intermediates. It was demonstrated that readthrough transcripts arose at a rate up to 7% of the normal viral RNA. RNA sequences downstream of the 3 ' long terminal repeat (LTR) acquired by polyadenylation signal readthrough could efficiently serve as templates for HIV-1 genetic recombination. The readthrough sequences downstream of the LTR appeared to be preferentially used for HIV-1 recombination when compared to homologous sequences located between the 5 ' and 3 ' LTRs.
Author: Wenfeng An
Language: English
Topic: HIV Research and Treatment
Subfield: Virology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2625699375