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Effects of 3' untranslated region mutations on plus-strand priming during moloney murine leukemia virus replication
1Department of Microbiology and Immunology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA.
Abstract:
A conserved purine-rich motif located near the 3' end of retroviral genomes is involved in the initiation of plus-strand DNA synthesis. We mutated sequences both within and flanking the Moloney murine leukemia virus polypurine tract (PPT) and determined the effects of these alterations on viral DNA synthesis and replication. Our results demonstrated that both changes in highly conserved PPT positions and a mutation that left only the cleavage-proximal half of the PPT intact led to delayed replication and reduced the colony-forming titer of replication defective retroviral vectors. A mutation that altered the cleavage proximal half of the PPT and certain 3' untranslated region mutations upstream of the PPT were incompatible with or severely impaired viral replication. To distinguish defects in plus-strand priming from other replication defects and to assess the relative use of mutant and wild-type PPTs, we examined plus-strand priming from an ectopic, secondary PPT inserted in U3. The results demonstrated that the analyzed mutations within the PPT primarily affected plus-strand priming whereas mutations upstream of the PPT appeared to affect both plus-strand priming and other stages of viral replication.
Insights
Mutations in the polypurine tract (PPT) of retroviral genomes significantly impact viral DNA synthesis and replication. Altering conserved PPT sequences or upstream regions impairs replication and viral vector efficiency.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Retroviral replication relies on specific genomic elements for DNA synthesis.
- The polypurine tract (PPT) is crucial for initiating plus-strand DNA synthesis.
Purpose of the Study:
- To investigate the role of the Moloney murine leukemia virus polypurine tract (PPT) in viral DNA synthesis and replication.
- To determine the impact of mutations within and flanking the PPT on retroviral replication.
Main Methods:
- Site-directed mutagenesis of the Moloney murine leukemia virus PPT and adjacent sequences.
- Analysis of viral DNA synthesis and replication efficiency using replication-defective retroviral vectors.
- Assessment of plus-strand priming using an ectopic PPT insertion in U3.
Main Results:
- Mutations in conserved PPT positions and partial PPT sequences delayed replication and reduced viral vector titers.
- Alterations in the cleavage-proximal PPT half and upstream 3' untranslated region severely impaired replication.
- Mutations within the PPT primarily affected plus-strand priming, while upstream mutations impacted priming and other replication stages.
Conclusions:
- The PPT is essential for efficient plus-strand DNA priming and overall retroviral replication.
- Specific sequences within the PPT and upstream regions play distinct roles in the viral replication cycle.