HMGA1 recruits CTIP2-repressed P-TEFb to the HIV-1 and cellular target promoters

Nucleic Acids Res. 2014 Apr;42(8):4962-71. doi: 10.1093/nar/gku168. Epub 2014 Mar 11.

Abstract

Active positive transcription elongation factor b (P-TEFb) is essential for cellular and human immunodeficiency virus type 1 (HIV-1) transcription elongation. CTIP2 represses P-TEFb activity in a complex containing 7SK RNA and HEXIM1. Recently, the inactive 7SK/P-TEFb small nuclear RNP (snRNP) has been detected at the HIV-1 core promoter as well as at the promoters of cellular genes, but a recruiting mechanism still remains unknown to date. Here we show global synergy between CTIP2 and the 7SK-binding chromatin master-regulator HMGA1 in terms of P-TEFb-dependent endogenous and HIV-1 gene expression regulation. While CTIP2 and HMGA1 concordingly repress the expression of cellular 7SK-dependent P-TEFb targets, the simultaneous knock-down of CTIP2 and HMGA1 also results in a boost in Tat-dependent and independent HIV-1 promoter activity. Chromatin immunoprecipitation experiments reveal a significant loss of CTIP2/7SK/P-TEFb snRNP recruitment to cellular gene promoters and the HIV-1 promoter on HMGA1 knock-down. Our findings not only provide insights into a recruiting mechanism for the inactive 7SK/P-TEFb snRNP, but may also contribute to a better understanding of viral latency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Gene Expression Regulation
  • HIV-1 / genetics*
  • HMGA1a Protein / metabolism*
  • Humans
  • Positive Transcriptional Elongation Factor B / metabolism*
  • Promoter Regions, Genetic*
  • Repressor Proteins / metabolism*
  • Tumor Suppressor Proteins / metabolism*

Substances

  • BCL11B protein, human
  • Repressor Proteins
  • Tumor Suppressor Proteins
  • HMGA1a Protein
  • Positive Transcriptional Elongation Factor B