Journal article
Identification of a novel isoform of Cdk9
Gene, Vol.307(1-2), pp.175-182
03/27/2003
DOI: 10.1016/S0378-1119(03)00466-9
PMID: 12706900
Abstract
Positive transcription factor b (P-TEFb) is required for RNA polymerase II to make the transition from abortive to productive elongation. This important factor is a heterodimer of a cyclin-dependent kinase, cyclin-dependent kinase 9 (Cdk9), and one of four cyclin partners, cyclin T1, T2a, T2b or K. We demonstrate here that there exists in cells a second form of Cdk9 that is 13 kDa larger than the protein originally identified. Both of these forms, which we name Cdk9(42) and Cdk9(55), are present in HeLa and NIH/3T3 cells. Cdk9(55) is generated from an mRNA that originates from a second promoter located upstream of the startpoint of transcription used to generate mRNAs encoding Cdk9(42). Antibodies specific for Cdk9(55) immunoprecipitate Cdk(55) and cyclin T1, but not Cdk9(42). Cdk9(55) in the immunoprecipitates is active as judged by its ability to phosphorylate the carboxyl-terminal domain of the largest subunit of RNA polymerase II. Recently it has been shown that the activity of P-TEFb is negatively regulated in cells by reversible association with a small cellular RNA called 7SK. We show here that P-TEFb molecules containing either form of Cdk9 are found in association with 7SK and both complexes are disrupted by treatment with 600 mM KCl. The relative abundance of Cdk9(55) and Cdk9(42) changes in different cell types, including HeLa, NIH/3T3, human macrophages and mouse lung tissue. Additionally, treatment of macrophages with lipopolysaccharides or infection with human immunodeficiency virus alters the relative abundance of the two forms of Cdk9.
Details
- Title: Subtitle
- Identification of a novel isoform of Cdk9
- Creators
- Sarah M Shore - Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USASarah A ByersWendy MauryDavid H Price
- Resource Type
- Journal article
- Publication Details
- Gene, Vol.307(1-2), pp.175-182
- Publisher
- Netherlands
- DOI
- 10.1016/S0378-1119(03)00466-9
- PMID
- 12706900
- ISSN
- 0378-1119
- eISSN
- 1879-0038
- Grant note
- GM 35500 / NIGMS NIH HHS AI 43691 / NIAID NIH HHS
- Language
- English
- Date published
- 03/27/2003
- Academic Unit
- Microbiology and Immunology; Biochemistry and Molecular Biology
- Record Identifier
- 9984024556702771
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