Functional analysis of six ORFs from Saccharomyces cerevisiae chromosome IV: two-spored asci produced by disruptant of YDR027c and strain-dependent DNA heterogeneity around YDR036c.

Six S. cerevisiae FY1679 heterozygous deletion mutants were made by replacing six open reading frames (ORFs) of the chromosome IV right arm with kanMX4 selection marker. Haploid and homozygous diploid deletion mutants were obtained from sporulation, dissection and mating experiments. No essential genes were found. The basic phenotypic analysis showed that the haploid and homozygous deletants for the ORF YDR027c (LUV1, VSP54 or RKI1) grew slowly. The diploid homozygous deletants for this ORF had a low frequency of sporulation. They produced asci with no more than one or two haploid spores and the majority of these spores formed were not viable. The deletion of the other ORFs, YDR022c (CIS1), YDR030c (RAD28), YDR032c (PST2), YDR033w (MRH1) and YDR036c, did not change the phenotypes tested in strain FY1679 or the first four ORFs in strain CEN.PK2. This work showed some differences in the DNA sequences between FY1679 and CEN.PK2: the regions immediately 1 kb upstream from YDR036c in these two strains are too different to hybridize properly, preventing deletion of YDR036c in the CEN.PK2 background by recombination with a disruption cassette designed for FY1679. In addition, there are different sets of transposable elements on the other side of the ORF, the differences starting at about 3.5 kb downstream from YDR036c.