C/EBPbeta regulates human immunodeficiency virus 1 gene expression through its association with cdk9.
Transcriptional regulation of the human immunodeficiency virus type 1 (HIV-1) is a complex event that requires the cooperative action of both viral (e.g. Tat) and cellular (e.g. C/EBPbeta, NF-kappaB) factors. The HIV-1 Tat protein recruits the human positive transcription elongation factor P-TEFb, consisting of cdk9 and cyclin T1, to the HIV-1 transactivation response (TAR) region. In the absence of TAR, Tat activates the HIV-1 long terminal repeat (LTR) through its association with several cellular factors including C/EBPbeta. C/EBPbeta is a member of the CCAAT/enhancer-binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of HIV-1 LTR. We examined whether Tat-C/EBPbeta association requires the presence of the P-TEFb complex. Using immunoprecipitation followed by Western blot, we demonstrated that C/EBPbeta-cyclin T1 association requires the presence of cdk9. Further, due to its instability, cdk9 was unable to physically interact with C/EBPbeta in the absence of cyclin T1 or Tat. Using kinase assays, we demonstrated that cdk9, but not a cdk9 dominant-negative mutant (cdk9-dn), phosphorylates C/EBPbeta. Our functional data show that co-transfection of C/EBPbeta and cdk9 leads to an increase in HIV-1 gene expression when compared to C/EBPbeta alone. Addition of C/EBP homologous protein (CHOP) inhibits C/EBPbeta transcriptional activity in the presence and absence of cdk9 and causes a delay in HIV-1 replication in T-cells. Together, our data suggest that Tat-C/EBPbeta association is mediated through cdk9, and that phosphorylated C/EBPbeta may influence AIDS progression by increasing expression of HIV-1 genes.
Mameli
Giuseppe
G
Section of Microbiology, Department of Biomedical Sciences, Center of Excellence for Biotechnology Development and Biodiversity Research, Sassari, Italy.|Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Deshmane
Satish L
SL
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Ghafouri
Mohammad
M
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Cui
Jianqi
J
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Simbiri
Kenneth
K
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Khalili
Kamel
K
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Mukerjee
Ruma
R
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Dolei
Antonina
A
Section of Microbiology, Department of Biomedical Sciences, Center of Excellence for Biotechnology Development and Biodiversity Research, Sassari, Italy.
Amini
Shohreh
S
Department of Biology, College of Science and Technology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.|Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
Sawaya
Bassel E
BE
Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D056906:Cyclin T; D042863:Cyclin-Dependent Kinase 9 / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D014162:Transfection; D020298:U937 Cells; D054322:tat Gene Products, Human Immunodeficiency Virus
D022782:CCAAT-Enhancer-Binding Protein-beta; C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D015696:Gene Products, tat; D054322:tat Gene Products, Human Immunodeficiency Virus; D042863:Cyclin-Dependent Kinase 9