Inhibition of HIV-1 transcription and replication by a newly identified cyclin T1 splice variant

J Biol Chem. 2013 May 17;288(20):14297-14309. doi: 10.1074/jbc.M112.438465. Epub 2013 Apr 8.

Abstract

A variety of cellular factors participates in the HIV-1 life cycle. Among them is the well characterized cyclin T1 (CYCT1). CycT1 binds to cyclin-dependent kinase 9 (CDK9) and forms the positive transcription elongation factor-b (P-TEFb). P-TEFb is then recruited by HIV-1 TAT to the HIV-1 long terminal repeat (LTR) promoter and subsequently leads to phosphorylation of the C-terminal domain of RNA polymerase II (pol II), enhanced processivity of pol II, and transcription of a full-length HIV-1 RNA. In this study, we report the identification of a new CYCT1 splice variant, designated as CYCT1b, and accordingly we renamed CYCT1 as CYCT1a. CYCT1b was detected in several cell lines, including primary human CD4 T cells, and its expression was subject to cell cycle regulation. Similar to CYCT1a, CYCT1b was primarily localized in the nucleus. CYCT1b expression was found to be inversely correlated with HIV-1 gene expression and replication. This inverse correlation appeared to involve TAT transactivation, CDK9 binding, and subsequent recruitment of P-TEFb to the HIV-1 LTR promoter and pol II C-terminal domain phosphorylation. In agreement with these findings, CYCT1b expression led to direct inhibition of TAT-transactivated transcription of the HIV-1 LTR promoter. Taken together, these results show that the newly identified CYCT1b splice variant inhibits HIV-1 transcription and may provide new clues for the development of anti-HIV strategies.

Keywords: Cyclins; Gene Regulation; HIV-1; HIV-1 Tat; RNA Polymerase II; Transcription.

Publication types

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

MeSH terms

  • Alternative Splicing
  • Amino Acid Sequence
  • Base Sequence
  • Cyclin T / genetics*
  • Cyclin T / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation, Viral*
  • HEK293 Cells
  • HIV-1 / metabolism*
  • HeLa Cells
  • Humans
  • Jurkat Cells
  • Molecular Sequence Data
  • Open Reading Frames
  • Phosphorylation
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • RNA, Messenger / metabolism
  • Transcription, Genetic*
  • Transcriptional Activation
  • Two-Hybrid System Techniques
  • tat Gene Products, Human Immunodeficiency Virus / metabolism*

Substances

  • CCNT1 protein, human
  • Cyclin T
  • Protein Isoforms
  • RNA, Messenger
  • tat Gene Products, Human Immunodeficiency Virus