U5 region of the human immunodeficiency virus type 1 long terminal repeat contains TRE-like cAMP-responsive elements that bind both AP-1 and CREB/ATF proteins

Virology. 1997 Jun 23;233(1):235-45. doi: 10.1006/viro.1997.8602.

Abstract

Activating protein-1 (AP-1) binding phorbol ester responsive elements (TRE) are located downstream of the transcription initiation site in the U5 region of the human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR). These downstream sequence elements, termed DSE, can bind cFos and junD and transmit protein kinase C (PKC) activation signals to the LTR. Further studies suggested the DSE might also bind AP-1-related proteins of the CREB/ATF family. Since enhanced HIV-1 expression is associated with activation of the cAMP-dependent protein kinase A (PKA) signaling pathway, we determined whether binding of CREB/ATF proteins to the DSE mediate cAMP/PKA activation of the HIV-1 LTR. In the present study. DSE binding complexes in nuclear protein extracta from colonic epithelial cells are shown to contain ATF-1, ATF-2, and CREB and transfection of either an ATF-2 or PKA expressing plasmid transactivated the DSE. Cholera toxin (Ctx), a potent activator of the cAMP/PKA pathway. Increased HIV-1 virus production from a latently infected promonocytic cell line, U1. Ctx increased LTR promoter activity and increased the CREB content of DSE binding complexes. Transfection of U1 cells with a series of mutant LTR reporter constructs demonstrated that the Ctx response was in large part mediated by the DSE. The Ctx response was also mediated by a heterologous promoter containing multiple TRE sites. Nuclear protein extracts from a T-cell line infected by HIV-1 contained higher levels of CREB/ATF proteins and manifested increased CREB/ATF binding activity. Collectively, these results indicate the DSE are TRE-like cAMP responsive elements that bind both AP-1 and CREB/ATF permitting induction of the HIV-1 LTR by both PKC and PKA activation signals.

Publication types

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

MeSH terms

  • Activating Transcription Factor 1
  • Activating Transcription Factor 2
  • Binding Sites
  • Cell Line
  • Cholera Toxin / metabolism
  • Cyclic AMP Response Element-Binding Protein / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • DNA-Binding Proteins*
  • HIV Long Terminal Repeat*
  • HIV-1 / chemistry
  • HIV-1 / genetics
  • HIV-1 / metabolism*
  • Humans
  • Transcription Factor AP-1 / metabolism*
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Tumor Cells, Cultured

Substances

  • ATF2 protein, human
  • Activating Transcription Factor 1
  • Activating Transcription Factor 2
  • Cyclic AMP Response Element-Binding Protein
  • DNA-Binding Proteins
  • Transcription Factor AP-1
  • Transcription Factors
  • Cholera Toxin
  • Cyclic AMP-Dependent Protein Kinases