DNA synthesis by HIV-1 reverse transcriptase at the central termination site: a kinetic study.

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Plus-strand DNA synthesis termination by HIV-1 RT is vital for viral infectivity.
• The central termination sequence features two sites (Ter1, Ter2) within A(n)T(m) motifs.
• Minor groove narrowing by A(n)T(m) motifs mediates DNA synthesis termination.

Purpose of the Study:

• To investigate the kinetic mechanisms of HIV-1 RT termination at the Ter2 site.
• To elucidate the role of DNA minor groove width in RT-mediated termination.
• To analyze the impact of A(n)T(m) tracts on nucleotide incorporation.

Main Methods:

• Kinetic analysis of HIV-1 RT binding and elongation in vitro.
• Utilized various DNA duplexes and triplexes surrounding the Ter2 terminator.
• Employed a simple kinetic scheme to interpret experimental data.

Main Results:

• HIV-1 RT exhibits significant affinity for the Ter2 DNA site.
• Nucleotide binding and incorporation rates are markedly reduced at Ter2.
• Minor groove narrowing directly impedes the final incorporation step.
• Elongation constraints persist downstream of the A(n)T(m) tract.

Conclusions:

• The A(n)T(m) tract's minor groove narrowing is the primary determinant of HIV-1 RT termination.
• Termination involves a significant hindrance of nucleotide incorporation, not just binding.
• Understanding these mechanisms offers insights into HIV-1 replication and potential therapeutic targets.