The HIV-1 Tat protein recruits a ubiquitin ligase to reorganize the 7SK snRNP for transcriptional activation

Elife. 2018 May 30;7:e31879. doi: 10.7554/eLife.31879.

Abstract

The HIV-1 Tat protein hijacks P-TEFb kinase to activate paused RNA polymerase II (RNAP II) at the viral promoter. Tat binds additional host factors, but it is unclear how they regulate RNAP II elongation. Here, we identify the cytoplasmic ubiquitin ligase UBE2O as critical for Tat transcriptional activity. Tat hijacks UBE2O to ubiquitinate the P-TEFb kinase inhibitor HEXIM1 of the 7SK snRNP, a fraction of which also resides in the cytoplasm bound to P-TEFb. HEXIM1 ubiquitination sequesters it in the cytoplasm and releases P-TEFb from the inhibitory 7SK complex. Free P-TEFb then becomes enriched in chromatin, a process that is also stimulated by treating cells with a CDK9 inhibitor. Finally, we demonstrate that UBE2O is critical for P-TEFb recruitment to the HIV-1 promoter. Together, the data support a unique model of elongation control where non-degradative ubiquitination of nuclear and cytoplasmic 7SK snRNP pools increases P-TEFb levels for transcriptional activation.

Keywords: 7SK snRNP; HIV-1; biochemistry; chemical biology; host-pathogen interactions; human; non-degradative ubiquitination; nuclear import; transcription elongation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Active Transport, Cell Nucleus / drug effects
  • Amino Acid Sequence
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Chromatin / metabolism
  • Dichlororibofuranosylbenzimidazole / pharmacology
  • HEK293 Cells
  • HIV-1 / metabolism*
  • HeLa Cells
  • Humans
  • Models, Biological
  • Nuclear Localization Signals / chemistry
  • Nuclear Localization Signals / metabolism
  • Positive Transcriptional Elongation Factor B / metabolism
  • Protein Binding / drug effects
  • Protein Transport / drug effects
  • RNA Interference
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / metabolism
  • Ribonucleoproteins, Small Nuclear / metabolism*
  • Transcriptional Activation / drug effects
  • Transcriptional Activation / genetics*
  • Ubiquitin-Conjugating Enzymes / chemistry
  • Ubiquitin-Conjugating Enzymes / metabolism*
  • Ubiquitination / drug effects
  • tat Gene Products, Human Immunodeficiency Virus / metabolism*

Substances

  • Chromatin
  • HEXIM1 protein, human
  • Nuclear Localization Signals
  • RNA-Binding Proteins
  • Ribonucleoproteins, Small Nuclear
  • tat Gene Products, Human Immunodeficiency Virus
  • Dichlororibofuranosylbenzimidazole
  • Ubiquitin-Conjugating Enzymes
  • UBE2O protein, human
  • Positive Transcriptional Elongation Factor B