Abstract
Transcription of HIV-1 genes depends on the RNA polymerase II kinase and elongation factor positive transcription elongation factor b (P-TEFb), the complex of cyclin T1 and CDK9. Recent evidence suggests that regulation of transcription by P-TEFb involves chromatin binding and modifying factors. To determine how P-TEFb may connect chromatin remodeling to transcription, we investigated the relationship between P-TEFb and histone H1. We identify histone H1 as a substrate for P-TEFb involved in cellular and HIV-1 transcription. We show that P-TEFb interacts with H1 and that P-TEFb inhibition by RNAi, flavopiridol, or dominant negative CDK9 expression correlates with loss of phosphorylation and mobility of H1 in vivo. Importantly, P-TEFb directs H1 phosphorylation in response to wild-type HIV-1 infection, but not Tat-mutant HIV-1 infection. Our results show that P-TEFb phosphorylates histone H1 at a specific C-terminal phosphorylation site. Expression of a mutant H1.1 that cannot be phosphorylated by P-TEFb also disrupts Tat transactivation in an HIV reporter cell line as well as transcription of the c-fos and hsp70 genes in HeLa cells. We identify histone H1 as a novel P-TEFb substrate, and our results suggest new roles for P-TEFb in both cellular and HIV-1 transcription.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Cyclin T / genetics
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Cyclin T / metabolism*
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Cyclin-Dependent Kinase 9 / genetics
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Cyclin-Dependent Kinase 9 / metabolism
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Flavonoids / pharmacology
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Gene Expression Regulation, Viral / drug effects
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Gene Expression Regulation, Viral / physiology*
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Genes, Viral / physiology*
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HIV Infections / genetics
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HIV Infections / metabolism
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HIV-1 / genetics
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HIV-1 / metabolism*
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HSP70 Heat-Shock Proteins / genetics
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HSP70 Heat-Shock Proteins / metabolism
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HeLa Cells
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Histones / genetics
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Histones / metabolism*
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Humans
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Multienzyme Complexes / genetics
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Multienzyme Complexes / metabolism
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Phosphorylation / drug effects
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Phosphorylation / genetics
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Piperidines / pharmacology
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Positive Transcriptional Elongation Factor B / genetics
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Positive Transcriptional Elongation Factor B / metabolism*
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Protein Kinase Inhibitors / pharmacology
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Proto-Oncogene Proteins c-fos / genetics
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Proto-Oncogene Proteins c-fos / metabolism
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tat Gene Products, Human Immunodeficiency Virus / genetics
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tat Gene Products, Human Immunodeficiency Virus / metabolism
Substances
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CCNT1 protein, human
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Cyclin T
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Flavonoids
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HSP70 Heat-Shock Proteins
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Histones
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Multienzyme Complexes
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Piperidines
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Protein Kinase Inhibitors
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Proto-Oncogene Proteins c-fos
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tat Gene Products, Human Immunodeficiency Virus
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alvocidib
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Positive Transcriptional Elongation Factor B
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CDK9 protein, human
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Cyclin-Dependent Kinase 9