Analysis of phosphorylation of YJL084c, a yeast protein

PCL6, PCL7(PAP1), and PHO80 belong to the PHO80 subfamily of PCLs (PHO85 cyclins), share high homology in protein sequences, and function with some similarity. YLR190w, the substrate of PCL7-PHO85, shares homology with YJL084c in a 140-amino-acid region. In addition, YJL084c was reported as a PCL6-binding protein. Here, it was found that there was association between YJL084c and PCL7, and their interaction was confirmed by co-immunoprecipitation assay and GST pull-down assay. The in vitro translational product of YJL084c could be phosphorylated by PCL7-PHO85 complex. Also, the GST fusion protein of the middle region expressed in E.coli could be phosphorylated, while the amino terminal or the carboxyl terminal could not. Interestingly, PCL6-PHO85 complex had the same characters; effect of phosphate condition on the phosphorylation was shown in both PCL6-PHO85 and PCL7-PHO85. YPH499: Yjl084c :: LEU2 was constructed by homologous recombination. PUT4 was reported as a YJL084c-binding protein, but no difference was observed between wild strain and the Yjl084c null mutant on MP medium. In addition, the interaction between PHO81 and all of the three cyclins was analyzed.