Functional characterization of a new member of the Cdk9 family in Aspergillus nidulans.
Cdk9-like kinases in complex with T-type cyclins are essential components of the eukaryotic transcription elongation machinery. The full spectrum of Cdk9/cyclin T targets, as well as the specific consequences of phosphorylations, is still largely undefined. We identify and characterize here a Cdk9 kinase (PtkA) in the filamentous ascomycete Aspergillus nidulans. Deletion of ptkA had a lethal effect in later stages of vegetative growth and completely impeded asexual development. Overexpression of ptkA affected directionality of polarized growth and the initiation of new branching sites. A green fluorescent protein-tagged PtkA version localized inside the nucleus during interphase, supporting a role of PtkA in transcription elongation, as observed in other organisms. We also identified a putative cyclin T homolog, PchA, in the A. nidulans genome and confirmed its interaction with PtkA in vivo. Surprisingly, the Pcl-like cyclin PclA, previously described to be involved in asexual development, was also found to interact with PtkA, indicating a possible role of PtkA in linking transcriptional activity with development and/or morphogenesis in A. nidulans. This is the first report of a Cdk9 kinase interacting with a Pcl-like cyclin, revealing interesting new aspects about the involvement of this Cdk-subfamily in differential gene expression.
Karlsruhe Institute of Technology, Institute of Applied Life Sciences, Microbiology, Hertzstr. 16, 76187 Karlsruhe, Germany. friederike.bathe@mbio.uka.de
Friederike
F
Bathe
Claudia
C
Kempf
Stephen A
SA
Osmani
Aysha H
AH
Osmani
Sabrina
S
Hettinger
Elke
E
Wohlmann
Reinhard
R
Fischer
D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D056906:Cyclin T / Q000378:metabolism; D042863:Cyclin-Dependent Kinase 9 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D016415:Sequence Alignment
D056906:Cyclin T; D005656:Fungal Proteins; D042863:Cyclin-Dependent Kinase 9