High-resolution view of HIV-1 reverse transcriptase initiation complexes and inhibition by NNRTI drugs.

Reverse transcription of the HIV-1 viral RNA genome (vRNA) is an integral step in virus replication. Upon viral entry, HIV-1 reverse transcriptase (RT) initiates from a host tRNA primer bound to the vRNA genome and is the target of key antivirals, such as non-nucleoside reverse transcriptase inhibitors (NNRTIs). Initiation proceeds slowly with discrete pausing events along the vRNA template.

Advances in understanding the initiation of HIV-1 reverse transcription.

Many viruses, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Human Immunodeficiency Virus (HIV), use RNA as their genetic material. How viruses harness RNA structure and RNA-protein interactions to control their replication remains obscure. Recent advances in the characterization of HIV-1 reverse transcriptase, the enzyme that converts its single-stranded RNA genome into a double-stranded DNA copy, reveal how the reverse transcription complex evolves during initiation.

Distinct Conformational States Underlie Pausing during Initiation of HIV-1 Reverse Transcription.

A hallmark of the initiation step of HIV-1 reverse transcription, in which viral RNA genome is converted into double-stranded DNA, is that it is slow and non-processive. Biochemical studies have identified specific sites along the viral RNA genomic template in which reverse transcriptase (RT) stalls. These stalling points, which occur after the addition of three and five template dNTPs, may serve as checkpoints to regulate the precise timing of HIV-1 reverse transcription following viral entry.

Crystal structures of DNA polymerase I capture novel intermediates in the DNA synthesis pathway.

High resolution crystal structures of DNA polymerase intermediates are needed to study the mechanism of DNA synthesis in cells. Here we report five crystal structures of DNA polymerase I that capture new conformations for the polymerase translocation and nucleotide pre-insertion steps in the DNA synthesis pathway. We suggest that these new structures, along with previously solved structures, highlight the dynamic nature of the finger subdomain in the enzyme active site.