Abstract
Positive transcription elongation factor b (P-TEFb) is a kinase that phosphorylates the carboxyl-terminal domain (CTD) of RNA Polymerase II (Pol II). Here, we show that flavopiridol, a highly specific P-TEFb kinase inhibitor, dramatically reduces the global levels of Ser2--but not Ser5--phosphorylated CTD at actively transcribed loci on Drosophila polytene chromosomes under both normal and heat shocked conditions. Brief treatment of Drosophila cells with flavopiridol leads to a reduction in the accumulation of induced hsp70 and hsp26 RNAs. Surprisingly, the density of transcribing Pol II and Pol II progression through hsp70 in vivo are nearly normal in flavopiridol-treated cells. The major defect in expression is at the level of 3' end processing. A similar but more modest 3' processing defect was also observed for hsp26. We propose that P-TEFb phosphorylation of Pol II CTD coordinates transcription elongation with 3' end processing, and failure to do so leads to rapid RNA degradation.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cells, Cultured
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Drosophila Proteins / genetics
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Drosophila Proteins / metabolism
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Drosophila melanogaster / cytology
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Drosophila melanogaster / genetics*
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Drosophila melanogaster / metabolism
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Enzyme Inhibitors / pharmacology
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Flavonoids / pharmacology
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HSP70 Heat-Shock Proteins / genetics
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HSP70 Heat-Shock Proteins / metabolism*
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Heat-Shock Proteins / genetics
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Heat-Shock Proteins / metabolism
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Hot Temperature
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Models, Genetic
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Phosphorylation
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Piperidines / pharmacology
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Positive Transcriptional Elongation Factor B / metabolism*
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Protein Structure, Tertiary
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RNA / analysis
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RNA / drug effects
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RNA / metabolism
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RNA Polymerase II / chemistry
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RNA Polymerase II / metabolism*
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RNA Processing, Post-Transcriptional*
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RNA, Small Interfering / metabolism
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Serine / drug effects
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Transcription, Genetic*
Substances
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Drosophila Proteins
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Enzyme Inhibitors
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Flavonoids
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HSP70 Heat-Shock Proteins
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Heat-Shock Proteins
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Piperidines
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RNA, Small Interfering
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Serine
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alvocidib
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RNA
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Positive Transcriptional Elongation Factor B
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RNA Polymerase II