APOBEC3G inhibits HIV-1 RNA elongation by inactivating the viral trans-activation response element

J Mol Biol. 2014 Jul 29;426(15):2840-53. doi: 10.1016/j.jmb.2014.05.012. Epub 2014 May 21.

Abstract

Deamination of cytidine residues in viral DNA is a major mechanism by which APOBEC3G (A3G) inhibits vif-deficient human immunodeficiency virus type 1 (HIV-1) replication. dC-to-dU transition following RNase-H activity leads to viral cDNA degradation, production of non-functional proteins, formation of undesired stop codons and decreased viral protein synthesis. Here, we demonstrate that A3G provides an additional layer of defense against HIV-1 infection dependent on inhibition of proviral transcription. HIV-1 transcription elongation is regulated by the trans-activation response (TAR) element, a short stem-loop RNA structure required for elongation factors binding. Vif-deficient HIV-1-infected cells accumulate short viral transcripts and produce lower amounts of full-length HIV-1 transcripts due to A3G deamination of the TAR apical loop cytidine, highlighting the requirement for TAR loop integrity in HIV-1 transcription. We further show that free single-stranded DNA (ssDNA) termini are not essential for A3G activity and a gap of CCC motif blocked with juxtaposed DNA or RNA on either or 3'+5' ends is sufficient for A3G deamination. These results identify A3G as an efficient mutator and that deamination of (-)SSDNA results in an early block of HIV-1 transcription.

Keywords: APOBEC3G; HIV-1; Tat; deamination; ssDNA.

Publication types

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

MeSH terms

  • APOBEC-3G Deaminase
  • Base Pairing
  • Base Sequence
  • Blotting, Northern
  • Cytidine Deaminase / metabolism*
  • DNA, Single-Stranded / genetics*
  • DNA, Viral / genetics*
  • Electrophoretic Mobility Shift Assay
  • HIV Reverse Transcriptase / antagonists & inhibitors
  • HIV Reverse Transcriptase / metabolism*
  • HIV-1 / physiology*
  • Humans
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • RNA, Viral / genetics
  • Response Elements / genetics*
  • Transcription, Genetic
  • Virus Activation / physiology*
  • Virus Replication
  • vif Gene Products, Human Immunodeficiency Virus / genetics

Substances

  • DNA, Single-Stranded
  • DNA, Viral
  • RNA, Viral
  • vif Gene Products, Human Immunodeficiency Virus
  • vif protein, Human immunodeficiency virus 1
  • HIV Reverse Transcriptase
  • APOBEC-3G Deaminase
  • APOBEC3G protein, human
  • Cytidine Deaminase