The sequence of a 8 kb segment on the right arm of yeast chromosome VII identifies four new open reading frames and the genes for yTAFII145

Genome-wide Transcriptional Dependence on TAF1 Functional Domains

Transcription factor IID (TFIID) plays a central role in regulating the expression of most eukaryotic genes. Of the 14 TBP-associated factor (TAF) subunits that compose TFIID, TAF1 is one of the largest and most functionally diverse. Yeast TAF1 can be divided into four regions including a putative histone acetyltransferase domain and TBP, TAF, and promoter binding domains. Establishing the importance of each region in gene expression through deletion analysis has been hampered by the cellular requirement of TAF1 for viability. To circumvent this limitation we introduced galactose-inducible deletion derivatives of previously defined functional regions of TAF1 into a temperature-sensitive taf1ts2 yeast strain. After galactose induction of the TAF1 mutants and temperature-induced elimination of the resident Taf1ts2 protein, we examined the properties and phenotypes of the mutants, including their impact on genome-wide transcription. Virtually all TAF1-dependent genes, which comprise approximately 90% of the yeast genome, displayed a strong dependence upon all regions of TAF1 that were tested. This finding might reflect the need for each region of TAF1 to stabilize TAF1 against degradation or may indicate that all TAF1-dependent genes require the many activities of TAF1. Paradoxically, deletion of the region of TAF1 that is important for promoter binding interfered with the expression of many genes that are normally TFIID-independent/SAGA (Spt-Ada-Gcn5-acetyltransferase)-dominated, suggesting that this region normally prevents TAF1 (TFIID) from interfering with the expression of SAGA-regulated genes.

Disruption of six novel genes from chromosome VII of Saccharomyces cerevisiae reveals one essential gene and one gene which affects the growth rate

Six ORFs of unknown function located on chromosome VII of Saccharomyces cerevisiae were disrupted in two different genetic backgrounds, and the phenotype of the generated mutants was analysed. Disruptions of ORFs YGR256w, YGR272c, YGR273c, YGR275w and YGR276c were carried out using the disruption marker kanMX4 flanked by short homology regions, whereas ORF YGR255c was inactivated with a long flanking homology (LFH) disruption cassette (Wach et al., 1994). Tetrad analysis of the heterozygous disruptants revealed that ORF YGR255c, previously identified as COQ6 and encoding a protein involved in the biosynthesis of coenzime Q (Tzagoloff and Dieckmann, 1990), is an essential gene. The same analysis also revealed that sporulation of the ygr272cDelta heterozygous diploid produced two small colonies per ascus that were also G418-resistant, indicating that the inactivation of ORF YGR272c could result in a slower growth rate. This result was confirmed by growth tests of the haploid disruptants and by complementation of the phenotype after transformation with a plasmid carrying the cognate gene. No phenotypes could be associated to the inactivation of ORFs YGR256w, YGR273c, YGR275w and YGR276c. Two of these genes have recently been further characterized: ORF YGR255w, renamed RTT102, encodes a regulator of the Ty1-element transposition, whereas ORF YGR276c was found to encode the 70 kDa RNase H activity and was renamed RNH70 (Frank et al., 1999).