Structural and functional analysis of cell cycle control genes in Cryptococcus neoformans

Abstract

Our group has reported the unique cell cycle pattern of the pathogenic yeast Cryptococcus neoformans, different from that of the model budding yeast Saccharomyces cerevisiae. To clarify the cell cycle mechanisms, homologues of cell cycle control genes in C. neoformans were cloned. We have reported the cloning of the CDC28/Cdc2 homologue, CnCdk1 and three Cdk1 cyclin homologues: two B‐type G2/M cyclins and a single G1 cyclin, CnCln1. Further search of the C. neoformans genome database however did not yield additional ORFs with G1 cyclin similarities. Sequence analysis and comparison with other cyclin sequences showed that CnCln1 possesses the typical amino acid residues conserved among G1 cyclins. Analysis of putative amino acid sequences of the C. neoformans CDC28/Cdc2, CnCdk1, revealed that it possesses the conserved motifs found in CDC28/Cdc2 homologues and is highly similar to the fission yeast Schizosaccharomyces pombe Cdc2 and S. cerevisiae CDC28. Notable however, is the difference in an amino acid residue in the well conserved Cdk PSTAIRE motif known to be involved in cyclin binding; in CnCdk1 alanine is changed to serine to become PSTSIRE. Further studies are currently being done to confirm their role and function in C. neoformans cell cycle. In order to analyze at the protein level, we have also been performing the proteomic analysis of the yeast cells.