Fig. 1. Cdk5 in U. maydis. (A) Schematic representation of the U. maydis Cdk5 protein in relation to human Cdk5 (HsCdk5) and S. cerevisiae Pho85 (ScPho85). The catalytic kinase domains are shown as gray boxes and were identified using the Simple Modular Architecture Research Tool (http://smart.embl-heidelberg.de). (B) Dendrogram of CDK-like proteins. The tree was reconstructed using the ClustalW method (http://www.ebi.ac.uk/clustalw/). Bar, 0.02 substitutions per amino acid. Note that U. maydis Cdk5 falls into the Cdk5/Pho85 subfamily of CDKs. An, Aspergillus nidulans; Sp, Schizosaccharomyces pombe; Ca, Candida albicans; Sc, Saccharomyces cerevisiae; Um, Ustilago maydis; Hs, Homo sapiens. (C) Protein levels at different stages of the cell cycle. Extracts from FB1 arrested at S or M phase, G1 phase enriched or an asynchronous culture (As) were assayed by western blot analysis using anti-PSTAIRE antibodies. Both Cdk1 and Cdk5 kinases were detected. (D) Cdk5-GFP appears in the cytoplasm and nucleus. Cells carrying a C-terminal Cdk5-GFP fusion were grown at exponential phase in CMD medium. Subcellular distribution of Cdk5-GFP (upper panels): cells at different phases of the cell cycle showed GFP signal in the nucleus. Only cells carrying large buds (i.e. undergoing mitosis) do not show nuclear fluorescence, probably because of disassembly of the nuclear envelope. In the lower row, DAPI staining co-localizes with the GFP signal. Bar, 10 µm.