Yeast heterozygous FHL1 deletion mutant

Forkhead transcription factor FHL1 gene was required for replicative lifespan as well as cell proliferation in yeast. In this study, to see how Fhl1p determines the lifespan, we performed a DNA microarray analysis of heterozygous diploid strain deleted for FHL1 and, from the Fhl1p-target genes, screened for a lifespan-related gene. Transcriptomic profiles showed large increases and moderate decreases in transcripts in the fhl1/FHL1 mutant. Pathway analysis suggested upregulation of most of carbon metabolisms (glycolysis, gluconeogenesis, and TCA cycle) and downregulation of translation (ribosomal proteins and translation factors) in the FHL1-deficient mutant. We found a remarkable downregulation of a set of phosphate metabolism genes and ribonucleotide reductase large subunit genes, RNR1 and RNR3. We demonstrated that Fhl1p regulates RNR1 gene transcription to maintain dNTP levels, modulating longevity against replication stress and genomic instability. Total RNA samples were prepared from wild-type BY4743 and its isogenic fhl1/FHL1 mutant cells grown in YPD medium at 30°C to OD600 of 1.0. Antisense RNA was synthesized and labeled with Cy3 for the fhl1/FHL1 mutant and with Cy5 for the wild type. Each mixture of Cy3- and Cy5-labeled antisense RNA was hybridized on a 3D-Gene Yeast Oligo Chip 6K (Toray, Kanagawa, Japan). The hybridized array was scanned with a 3D-Gene Scanner 3000 (Toray).