are still poorly understood. Yap1p activates transcription http://www.selleckchem.com/products/Y-27632.html by binding to specific DNA sequences located in the promoter of its target genes. Currently, four predicted Yap1p binding sites have been identified in hundreds of genes. Obvi ously, the Yap1 regulated adaptation to various stimuli strongly depends on the expression of these target genes. To gain insights into how Yap1p regulates the protective response and how the yeast cell adapts to a changing en vironment, it is very important to get a global overview of changes in expression of these target genes. DNA microarrays provide a practical and economical tool for studying expression of nearly every gene in yeast. This approach can, in principle, be used to identify all the transcription targets of regulatory pro teins like Yap1p.

However, accumulating evidence indi cates that mRNA abundance does not always correlate well with protein expression levels. The present study was conducted to explore the changes in expres sion of Yap1p targeted proteins at the proteome level. For this purpose, we utilized an S. cerevisiae transfor mant overexpressing Yap1p and performed triplicate analyses of the proteome by two dimensional gel elec trophoresis. Proteins of interest were identified using mass spectrometry. This study provides the mapping of the Yap1p targeted proteins in S. cerevisiae and offers a global overview of the ubiquitous cellular changes elicited by overexpression of this important yeast transcription factor. To our knowledge this is the first report on the effect of Yap1 overexpression on the yeast proteome.

Results Overexpression of Yap1p in S. cerevisiae To obtain a global overview of the in vivo Yap1p targets at the proteome level of S. cerevisiae, a comparative ana lysis was performed using a yeast transformant harbor ing a control plasmid and a transformant with a plasmid carrying the YAP1 gene. Considering the possibility to control pH and maintain anaerobic conditions, yeast transformants were cultivated in a multi bioreactor and the fermentation was discontinued when the cells were still in the exponential growth phase. Before 2 DE ana lysis, overexpression of Yap1p was validated by western blot analysis. As expected, the Yap1 protein was present at elevated levels in the Yap1p Batimastat overexpressing transfor mant. The level was estimated to be approx. four fold higher than in the control transformant.

2 DE analyses of protein extracts from S. useful handbook cerevisiae Yeast cells from both cultures were harvested and pro teins were extracted using the extraction protocol devel oped by Kolkman et al. which we further optimized for our yeast samples. In the protocol developed by Kolkman et al. the cells are lyophilized and subse quently vortexed with glass beads prior to boiling with SDS. In order to improve cell disruption, we introduced an additional step. Before the SDS boiling, the yeast cells were disrupted in extraction buffer containing thiourea. Cell debris which was not dissolved in the extr