Activating protein-1 cooperates with phorbol ester activation signals to increase HIV-1 expression.
OBJECTIVE
To determine whether Jun and Fos, components of the activating protein-1 (AP-1) transcription factor, transactivate HIV-1 proviral expression.


METHODS
The effects of phorbol myristate acetate (PMA) and Jun or Fos transcription factors on HIV-1 expression were investigated using a provirus clone and long terminal repeat (LTR)-reporter gene constructs. The influence of PMA stimulation on AP-1 binding activity was determined with antibodies in gel mobility shift assays.


METHODS
Activation of HIV-1 provirus and transcription of HIV-1 LTR sequences in response to cotransfection of Jun or Fos expression plasmids into a permissive colon cancer cell line, SW480, were assessed by p24 core antigen capture and reporter gene assays, respectively. The effect of protein kinase C activation was evaluated by comparing cells grown in the presence or absence of PMA (20 ng/ml).


RESULTS
Cotransfection of HIV-1 provirus and expression plasmids for c-Jun or JunB into SW480 cells resulted in increased p24 core antigen and this response was markedly increased following PMA stimulation of cells. c-Fos or JunD alone did not increase p24 production but markedly increased p24 production in PMA-stimulated cells. PMA increased c-Fos and JunD binding activity on an AP-1 binding site within the U5 region of the LTR, as shown in gel mobility shift assays. Functional analysis of this site by transient transfections demonstrated it was required to mediate c-Fos and JunD transactivation of the HIV-1 LTR.


CONCLUSIONS
Specific Jun and Fos transcription factors can transactivate the HIV-1 provirus and this response is markedly increased in cooperation with cellular activation signals elicited by PMA. Taken together, the data indicate that AP-1 binding sites downstream of the transcriptional start site in the HIV-1 LTR are capable of binding c-Fos and JunD and may contribute to transactivation of HIV-1 provirus.
Roebuck
K A
KA
Department of Immunology and Microbiology, Rush Presbyterian-St Luke's Medical Center, Chicago, Illinois 60612, USA.
Gu
D S
DS
Kagnoff
M F
MF
D003110:Colonic Neoplasms; D004279:DNA, Viral / Q000378:metabolism; D004789:Enzyme Activation; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D015696:Gene Products, tat / Q000235:genetics / Q000502:physiology; D016655:HIV Core Protein p24 / Q000096:biosynthesis; D016325:HIV Long Terminal Repeat / Q000235:genetics; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011533:Proviruses; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D054322:tat Gene Products, Human Immunodeficiency Virus
D004279:DNA, Viral; D015696:Gene Products, tat; D016655:HIV Core Protein p24; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D054322:tat Gene Products, Human Immunodeficiency Virus; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate