The Medicago CDKC;1-CYCLINT;1 kinase complex phosphorylates the carboxy-terminal domain of RNA polymerase II and promotes transcription.
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.
Fülöp
Katalin
K
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
Pettkó-Szandtner
Aladàr
A
Magyar
Zoltán
Z
Miskolczi
Pál
P
Kondorosi
Eva
E
Dudits
Dénes
D
Bakó
László
L
D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism; D056906:Cyclin T; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006367:HeLa Cells; D006801:Humans; D029902:Medicago / Q000201:enzymology*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D009097:Multienzyme Complexes; D010940:Plant Proteins; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II