| Summary: | 碩士 === 國立陽明大學 === 遺傳學研究所 === 94 === On the basis of a genome-wide screen, BUD23 deletion mutant displays a random budding phenotype in diploid cells, indicating that BUD23 participates in the biplolar bud-site selection. I characterized the bud23 null mutant of haploid cells, and it also showed a random budding phenotype. It is also predicted that Bud23p is a class I methyltransferase. Disruption of BUD23 in haploid cells showed a slow growth phenotype. Here, I generated two point mutations, D77A and G57R, on the putative AdoMet binding site of Bud23p by site-directed mutagenesis. While over-expression of Bud23p(D77A) in bud23Δ/bud23Δ null mutant could compensate random budding and slow growth phenotypes, however, over-expressing Bud23p(G57R) failed to rescue the slow growth phenotype. Moreover, in these cells, bud scars were hardly seen, and new phenotypes were observed. The new phenotypes resulting from over-expressing the G57R mutant included non-dividing cells, abnormally elongated buds, chitin delocalized at the bud neck and mis-segregation of nucleus. All the observed phenotypes were similar to that of septin mutants, suggesting that G57R mutant blocked septin ring formation.
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