Role of RNA structural plasticity in modulating HIV-1 genome packaging and translation

Area of Science:

• Molecular Biology
• Virology
• Biophysics

Background:

• HIV-1 (Human Immunodeficiency Virus type 1) RNA packaging into progeny virions is a complex process.
• Twinned transcriptional start site usage, producing RNAs with single (1G) or triple (3G) guanosine initiation, influences RNA fate.
• The 5' polyA element plays a role in RNA structure and function.

Purpose of the Study:

• To investigate how structural remodeling of the 5' polyA element in HIV-1 transcripts affects RNA packaging and translation.
• To determine the role of 5' cap exposure in viral genome packaging.

Main Methods:

• In vitro biophysical studies.
• In-cell genome packaging assays.
• Competitive translation assays.
• Analysis of native and 5' polyA mutant transcripts.

Main Results:

• Mutations stabilizing the 5' polyA hairpin in 3G RNAs promoted RNA dimerization and Gag binding without cap sequestration.
• 3G transcripts with stabilized hairpin structures were not competitively packaged.
• 5' cap exposure correlated with poor packaging and efficient translation for all examined RNAs.

Conclusions:

• 5' cap exposure is a critical determinant for HIV-1 genome packaging.
• Structural plasticity of the 5' leader region regulates HIV-1 transcript structure and function.
• Thermodynamic control of RNA structure influences viral RNA fate.