in their own right, and whose identity will emerge upon examination of a larger number of fungal kinomes. Of the 5 microsporidian kinases included in the ‘Other’ group, only 3 could be mapped to homologous proteins in S. cerevisiae and S. pombe. CAD25400.1 is the homologue of Bud32, which we have also now shown to be present in fission yeast. Although named for its apparent role in S. cerevisiae bud site selection, more recent studies have identified Bud32p kinase as a component of a conserved protein complex with important roles in transcription and telomere maintenance, and it is likely that these roles explain its presence in E. cuniculi. CAD24933.1 is the orthologue of the essential polo kinase, a conserved cell cycle regulatory kinase with many important roles in centrosome and spindle function, sister chromatid cohesion, kinetochore function and mitotic PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19796427 exit. A key feature of Polo kinases is the presence of tandem Polo Box sequences in the C-terminal nonkinase domain, which like 14-3-3 proteins are a phosphopeptide binding domain that target the kinase to substrates phosphorylated by other kinases. Although the E. cuniculi kinase lacks these characteristic Cterminal Polo boxes in a Pfam domain search, manual inspection of the C-terminal region provides evidence for two degenerate Polo box sequences, confirming the identity of this kinase as a Polo homologue. Page 14 of 21 BMC buy CJ-023423 Genomics 2007, 8:309 http://www.biomedcentral.com/1471-2164/8/309 The third readily-assignable E. cuniculi kinase in the ‘Other’ group is an orthologue of budding yeast Swe1p and fission yeast Wee1 and Mik1. These kinases are negative regulators of the Cdc28p/Cdc2 CDK kinases that regulate the time of entry into mitosis. This is an essential and critical role in fission yeast, where loss of both paralogous kinases causes catastrophic premature mitotic entry, whereas in budding yeast the effects of Swe1p are more subtle and cells can manage without it, at least under normal circumstances. Protein kinases in the ‘Other’ group that are shared by the two model yeasts but that are not conserved in the microsporidian include Gcn2p, Ire1p, the Ark1p-related kinases required for regulating cortical actin function and endocytosis and Vps15p, and their fission yeast orthologues. Atypical protein kinases Only aPKs of the PIKK and RIO families were identified in the E. cuniculi genome, and putative homology could be assigned in all three cases. CAD25142.1 and CAD25955.1 are related to budding yeast Tel1p and are likely to be involved in telomere maintenance and the DNA damage checkpoint response as discussed above. The TOR group of PIKK members are involved in nutrient sensing pathways and are not represented in the microsporidian. A homologue of Tra1p, apparently conserved between the two yeast species, was also not evident despite its essential role as a core component of the SAGA and NuA4 histone acetyl transferase complexes in budding yeast that are important for transcriptional activation, particularly involving acidic activators. It is not clear how E. cuniculi can dispense with such a function, although many of the components of the yeast SAGA and NuA4 com- Page 15 of 21 BMC Genomics 2007, 8:309 http://www.biomedcentral.com/1471-2164/8/309 plexes are not essential for viability. The Rio kinases are required for 20S prerRNA processing, a role which is apparently conserved in E. cuniculi. Finally, E. cuniculi lacks a pyruvate dehydrogenase kinase, an enzyme that dow