Recruitment of SWI/SNF to the Human Immunodeficiency Virus Type 1 Promoter

AUTOR(ES)

Henderson, Angus

FONTE

American Society for Microbiology

RESUMO

Following human immunodeficiency virus type 1 (HIV-1) integration into the host cell's genome, the 5′ long terminal repeat (LTR) is packaged into a highly specific chromatin structure comprised of an array of nucleosomes positioned with respect to important DNA sequence elements that regulate the transcriptional activity of the provirus. While several host cell factors have been shown to be important for chromatin remodeling and/or basal transcription, no specific mechanism that relieves the transcriptional repression imposed by nuc-1, a positioned nucleosome that impedes the start site of transcription, has been found. Since phorbol esters cause the rapid disruption of nuc-1 and markedly stimulate HIV-1 transcription, we looked for protein factors that associate with this region of the HIV-1 promoter in a phorbol-ester-dependent manner. We report here that ATF-3, JunB, and BRG-1 (the ATPase subunit of the 2-MDa human chromatin remodeling machine SWI/SNF) are recruited to the 3′ boundary of nuc-1 following phorbol myristate acetate stimulation in Jurkat T cells. Analysis of the recruitment of BRG-1 in nuclear extracts prepared from Jurkat T cells and reconstitution of an in vitro system with purified components demonstrate that ATF-3 is responsible for targeting human SWI/SNF (hSWI/SNF) to the HIV-1 promoter. Importantly, this recruitment of hSWI/SNF required HMGA1 proteins. Further support for this conclusion comes from immunoprecipitation experiments showing that BRG-1 and ATF-3 can exist together in the same complex. Although ATF-3 clearly plays a role in the specific targeting of BRG-1 to the HIV-1 promoter, the maintenance of a stable association between BRG-1 and chromatin appears to be dependent upon histone acetylation. By adding BRG-1 back into a BRG-1-deficient cell line (C33A cells), we demonstrate that trichostatin A strongly induces the 5′-LTR-driven reporter transcription in a manner that is dependent upon BRG-1 recruitment.

Documentos Relacionados

• Recruitment of the SWI/SNF chromatin remodeling complex by transcriptional activators
• Recruitment of SWI/SNF by Gcn4p Does Not Require Snf2p or Gcn5p but Depends Strongly on SWI/SNF Integrity, SRB Mediator, and SAGA
• Loss of the Brm-Type SWI/SNF Chromatin Remodeling Complex Is a Strong Barrier to the Tat-Independent Transcriptional Elongation of Human Immunodeficiency Virus Type 1 Transcripts▿ †
• Transcriptional Activation Domains of Human Heat Shock Factor 1 Recruit Human SWI/SNF
• Mitotic inactivation of a human SWI/SNF chromatin remodeling complex