STRUCTURAL AND PHYLOGENETIC ANALYSIS OF THE ACTIN GENE FROM THE YEASTPHAFFIA-RHODOZYMA

The gene coding for actin from Phaffia rhodozyma was cloned and sequen ced. The Phaffia actin gene contains four intervening sequences and th e predicted protein consists of 375 amino acids. The structural featur es of the Phaffia actin introns were studied and compared with actin i ntrons from seven fungi and yeasts with ascomycetous and basidiomyceto us affinity. It was shown that the architecture of the Phaffia introns most resembles that of the basidiomycete Filobasidiella neoformans (p erfect stage of Cryptococcus neoformans), whereas least resemblance oc curs with the ascomycetous yeasts. Based on the intron structure, the ascomycetous yeasts can be accommodated in one group in that their spl ice site sequences are very similar and show less homology with the ot her fungi investigated, including Phaffia. It was demonstrated that th e Phaffia actin introns cannot be spliced in Saccharomyces cerevisiae, which shows that the differences found in intron structure are signif icant. Alignment of the Phaffia actin gene with the actin sequences fr om the yeasts and fungi investigated showed a high level of homology b oth on the DNA level and on the protein level. Based on these alignmen ts Phaffia showed highest homology with F. neoformans and both organis ms were accommodated in the same cluster. In addition, the actin gene comparisons also supported the distant relationship of Phaffia with th e ascomycetous yeasts. These results supported the usefulness of actin sequences for phylogenetic studies. The sequence presented here has b een submitted to the EMBL data library under Accession Number X89898.