Latest documents http://publikationen.ub.uni-frankfurt.de/index/index/ Tue, 14 Aug 2012 17:10:36 +0200 Tue, 14 Aug 2012 17:10:36 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25647 Amino acids can induce yeast cell adhesion but how amino acids are sensed and signal the modulation of the FLO adhesion genes is not clear. We discovered that the budding yeast Saccharomyces cerevisiae CEN.PK evolved invasive growth ability under prolonged nitrogen limitation. Such invasive mutants were used to identify amino acid transporters as regulators of FLO11 and invasive growth. One invasive mutant had elevated levels of FLO11 mRNA and a Q320STOP mutation in the SFL1 gene that encodes a protein kinase A pathway regulated repressor of FLO11. Glutamine-transporter genes DIP5 and GNP1 were essential for FLO11 expression, invasive growth and biofilm formation in this mutant. Invasive growth relied on known regulators of FLO11 and the Ssy1-Ptr3-Ssy5 complex that controls DIP5 and GNP1, suggesting that Dip5 and Gnp1 operates downstream of the Ssy1-Ptr3-Ssy5 complex for regulation of FLO11 expression in a protein kinase A dependent manner. The role of Dip5 and Gnp1 appears to be conserved in the S. cerevisiae strain ∑1278b since the dip5 gnp1 ∑1278b mutant showed no invasive phenotype. Secondly, the amino acid transporter gene GAP1 was found to influence invasive growth through FLO11 as well as other FLO genes. Cells carrying a dominant loss-of-function PTR3647::CWNKNPLSSIN allele had increased transcription of the adhesion genes FLO1, 5, 9, 10, 11 and the amino acid transporter gene GAP1. Deletion of GAP1 caused loss of FLO11 expression and invasive growth. However, deletions of FLO11 and genes encoding components of the mitogen-activated protein kinase pathway or the protein kinase A pathway were not sufficient to abolish invasive growth, suggesting involvement of other FLO genes and alternative pathways. Increased intracellular amino acid pools in the PTR3647::CWNKNPLSSIN-containing strain opens the possibility that Gap1 regulates the FLO genes through alteration of the amino acid pool sizes. Rasmus Torbensen; Henrik Devitt Møller; David Gresham; Sefa Alizadeh; Doreen Ochmann; Eckhard Boles; Birgitte Regenberg article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25647 Tue, 14 Aug 2012 17:10:36 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1906 Background The growth rate is central for the development of cells in all organisms. However, little is known about the impact of changing growth rates. We have used continuous cultures to control the growth rate and study the transcriptional programme of the model eukaryote Saccharomyces cerevisiae with generation times varying between 2 and 35 hours. Results A total of 5,930 transcripts were identified at the different growth rates studied. Consensus clustering of these revealed that half of all yeast genes are affected by the specific growth rate, and that the changes are similar to those found when cells are exposed to different types of stress (more than 80% overlap). Genes with decreased transcript levels in response to faster growth are largely of unknown function (more than 50%) while genes with increased transcript levels are involved in macromolecular biosynthesis such as those encoding ribosomal proteins. This group also covers most targets of the transcriptional activator, RAP1, which is also known to be involved in replication. A positive correlation between the location of replication origins and the location of growth-regulated genes, suggests a role for replication in growth rate regulation. Conclusions Our data show that the cellular growth rate has paramount influence on transcriptional regulation. This, in turn, implies that one should be cautious when comparing mutants with different growth rates. The results also indicate that much of the regulation is coordinated via the chromosomal location of the affected genes, which may be valuable information for the control of heterologous gene expression in metabolic engineering. Birgitte Regenberg; Thomas Grotkjær; Winther. Ole; Anders Fausbøll; Mats Åkesson; Christoffer Bro; Lars Kai Hansen; Søren Brunak; Jens Nielsen article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/1906 Thu, 07 Dec 2006 15:02:58 +0100