Medicago CDKC;1-CYCLINT;1 kinase complex phosphorylates the carboxy-terminal domain of RNA polymerase II and promotes transcription

• Published in: The Plant journal : for cell and molecular biology Vol. 42; no. 6; pp. 810 - 820
• Main Authors: Fulop, K, Pettko-Szandtner, A, Magyar, Z, Miskolczi, P, Kondorosi, E, Dudits, D, Bako, L
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.06.2005; Blackwell Science; Blackwell Publishing Ltd; Wiley
• Subjects: alfalfa; Amino Acid Sequence; amino acid sequences; Biological and medical sciences; CDK‐cyclin complex; cell cycle; Cell kinetics; Cell Nucleus - metabolism; Cell physiology; CTD kinase; Cyclin T; Cyclin-dependent kinases; Cyclin-Dependent Kinases - metabolism; cyclin-dependent protein kinases; Cyclins - metabolism; DNA-directed RNA polymerase; enzyme activity; Flowers & plants; forage crops; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant; HeLa Cells; Humans; Life Sciences; Medicago; Medicago - enzymology; Medicago sativa; Molecular Sequence Data; Multienzyme Complexes - metabolism; nucleotide sequences; Other; Plant physiology and development; plant proteins; Plant Proteins - metabolism; protein kinases; protein phosphorylation; protein-protein interactions; Proteins; P‐TEFb; RNA polymerase; RNA Polymerase II - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; transcription; transcription (genetics); Transcription, Genetic; Phosphorylation; Transcription; Enzyme; Transferases; CTD kinase; Medicago sativa; CDK-cyclin complex; Homology; Molecular interaction; Medicago; DNA-directed RNA polymerase; P-TEFb; Nucleotidyltransferases; Regulation(control); Leguminosae; Enzymatic activity; Kinase; Dicotyledones; Angiospermae; Cell cycle; Spermatophyta; Cyclin dependent kinase; Sequence Homology; Genetic; Plant; Amino Acid; Gene Expression Regulation
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2005.02421.x

The Ms;CDKC;1 kinase is structurally similar to those cyclin-dependent kinases (CDKs) that are not involved directly in cell cycle regulation. The presence of a PITAIRE motif in Ms;CDKC;1 suggests that it interacts with cyclins different from known PSTAIRE/PPTALRE kinase regulatory subunits. Here we demonstrate that a Medicago CYCLINT (CYCT) protein is a specific interactor of Ms;CDKC;1 and the interaction between these two proteins gives rise to an active kinase complex that localizes to the nucleus and phosphorylates the carboxy-terminal YSPTSPS heptapeptide repeat domain (CTD) of the largest subunit of RNA polymerase II in vitro. Mutation of Ser to Ala at position 5 within the heptapeptide repeat abolishes substrate phosphorylation by the Ms;CDKC;1 kinase complex. Furthermore, our data show that addition of the Medicago CDKC;1-CYCT;1 heterodimer completely restored the transcriptional activity of a HeLa nuclear extract depleted of endogeneous CDK9 kinase complexes. Together, these results indicate that the Medicago CDKC;1-CYCT;1 complex is a positive regulator of transcription in plants and has a role similar to the CDK9/cyclin T complex of human positive transcription elongation factor P-TEFb.