Journal Article

HIV-1 Tat interactions with cellular 7SK and viral TAR RNAs identifies dual structural mimicry

Smith, Janet L., Pham, Vincent V., Humbert, Nicolas, Brown, W. Clay, Meagher, Jennifer L., Khan, Shamsun Nahar, de Rocquigny, Hugues, Salguero, Carolina, D’Souza, Victoria M.

2018

Overview

The HIV Tat protein competes with the 7SK:HEXIM interaction to hijack pTEFb from 7SK snRNP and recruit it to the TAR motif on stalled viral transcripts. Here we solve structures of 7SK stemloop-1 and TAR in complex with Tat’s RNA binding domain (RBD) to gain insights into this process. We find that 7SK is peppered with arginine sandwich motifs (ASM)—three classical and one with a pseudo configuration. Despite having similar RBDs, the presence of an additional arginine, R52, confers Tat the ability to remodel the pseudo configuration, required for HEXIM binding, into a classical sandwich, thus displacing HEXIM. Tat also uses R52 to remodel the TAR bulge into an ASM whose structure is identical to that of the remodeled ASM in 7SK. Together, our structures reveal a dual structural mimicry wherein viral Tat and TAR have co-opted structural motifs present in cellular HEXIM and 7SK for productive transcription of its genome. The HIV Tat protein recruits a host elongation factor from the cellular 7SK complex to the viral TAR RNA to ensure transcriptional elongation. Here, Pham et al. solve the structures of both 7SK and TAR RNAs in complex with Tat’s RNA binding domain and gain mechanistic insights into the process.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 101/6 / 631/326/596/2557 / 631/337/572 / 631/535/878/1263 / 692/699/255/1901 / Arginine / Binding / Biochemistry, Molecular Biology / Cellular structure / Competition / Configurations / Genomes / HIV / Human immunodeficiency virus / Humanities and Social Sciences / Humans / Life Sciences / Magnetic Resonance Spectroscopy / Microbiology and Parasitology / Mimicry / Molecular Mimicry / multidisciplinary / NMR / Nuclear magnetic resonance / Nucleic Acid Conformation / Proteins / Ribonucleic acid / Ribonucleoproteins (small nuclear) / Ribonucleoproteins, Small Nuclear - metabolism / RNA / RNA polymerase / RNA, Viral - chemistry / RNA, Viral - metabolism / RNA-Binding Proteins - metabolism / Science / Science (multidisciplinary) / Structural Biology / tat Gene Products, Human Immunodeficiency Virus - metabolism / Tat protein / Transcription / Virology