HIV latency reversing agents act through Tat post translational modifications

Area of Science:

• Virology
• Molecular Biology
• Epigenetics

Background:

• Latency reversing agents (LRAs) aim to reactivate HIV from latent reservoirs.
• Limited understanding exists on how LRAs interact with the HIV protein Tat, especially concerning Tat's basic residues and their modifications impacting transcription and RNA processing.

Purpose of the Study:

• To investigate the role of Tat's basic residues and post-translational modifications in HIV reactivation by LRAs.
• To elucidate the mechanisms by which LRAs like histone deacetylase inhibitors (HDACi) and JQ1 interact with Tat.

Main Methods:

• Site-directed mutagenesis of Tat protein, focusing on lysine and arginine residues.
• Assays to measure HIV transcription and mRNA splicing.
• Evaluation of LRAs (HDACi, JQ1) in the presence and absence of wild-type and mutant Tat.

Main Results:

• Mutations in Tat's lysine (K28, K50) and arginine residues reduced its ability to induce transcription and splicing.
• Acetylation and methylation of Tat K28 and K50 were critical for Tat's transcriptional control and response to HDACi and JQ1.
• JQ1 uniquely induced HIV mRNA splicing independently of Tat and rescued splicing in Tat lysine mutants via BRD4.

Conclusions:

• Tat's co-transcriptional RNA processing and transcriptional initiation/processivity are vital for latent HIV reactivation.
• HDACi and JQ1 enhance transcription with Tat, but JQ1 additionally facilitates post-transcriptional splicing.
• Tat residues K28 and K50, along with their modifications, are crucial for LRA synergy with Tat during HIV reactivation.