title: C/EBPbeta regulates human immunodeficiency virus 1 gene expression through its association with cdk9.
abstract: 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.
authors.affiliation: 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.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mameli
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Satish L
authors.initials: SL
authors.lastname: Deshmane
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ghafouri
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Jianqi
authors.initials: J
authors.lastname: Cui
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Simbiri
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Kamel
authors.initials: K
authors.lastname: Khalili
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Ruma
authors.initials: R
authors.lastname: Mukerjee
authors.affiliation: Section of Microbiology, Department of Biomedical Sciences, Center of Excellence for Biotechnology Development and Biodiversity Research, Sassari, Italy.
authors.forename: Antonina
authors.initials: A
authors.lastname: Dolei
authors.affiliation: 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.
authors.forename: Shohreh
authors.initials: S
authors.lastname: Amini
authors.affiliation: Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA.
authors.forename: Bassel E
authors.initials: BE
authors.lastname: Sawaya
mesh_terms: 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
chemical_list: 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