Abstract
The MCM (mini-chromosome maintenance) genes have a well established role in the initiation of DNA replication and in the elongation of replication forks in Saccharomyces cerevisiae. In this study we demonstrate elevated expression of sub-telomeric and Ty retrotransposon-proximal genes in two mcm5 strains. This pattern of up-regulated genes resembles the genome-wide association of MCM proteins to chromatin that was reported earlier. We link the altered gene expression in mcm5 strains to a reversal of telomere position effect (TPE) and to remodeling of sub-telomeric and Ty chromatin. We also show a suppression of the Ts phenotype of a mcm5 strain by the high copy expression of the TRA1 component of the chromatin-remodeling SAGA/ADA (SPT-ADA-GCN5 acetylase/ADAptor). We propose that MCM proteins mediate the establishment of silent chromatin domains around telomeres and Ty retrotransposons.
Highlights
The MCM genes have a well established role in the initiation of DNA replication and in the elongation of replication forks in Saccharomyces cerevisiae
Analysis of Differential Gene Expression in mcm5 Strains— An earlier analysis of gene expression of the mcm5-461 strain has indicated that several COS genes, which are positioned next to telomeres, were up-regulated at 37 °C compared with 30 °C (Ref. 38 and data not shown)
In this report we show that mutations in MCM5 lead to de-repression of genes that are close to telomeres and Tytransposable elements
Summary
Positive clones were selected on SC/-Leu plates and on YPD (1% yeast extract, 2% peptone, 2% glucose) plates at 37 °C. Microarray Analysis of Gene Expression—Mutant mcm and complemented mcm5::MCM5 strains were grown in YPD at 30 °C or 37 °C to A600 ϭ 0.2– 0.5 and harvested on crushed ice. Total RNA was isolated by the lithium chloride method and cDNA was synthesized from 10 g of total RNA by reverse transcribing with SuperScript II (Stratagene) in the presence of amino-allyl dUTP. Expressed genes were identified as 2-fold up- or down-regulated and clustered for n number of experiments with GeneSpring version 5.0 software (Silicon Genetics). ORFs that are up-or down-regulated at least 2-fold in at least three out of four experiments were obtained with GeneSpring version 5.0. The genome position of each ORF was obtained from mips.gsf.de/proj/yeast. Cell cycle-regulated genes were obtained from Ref. 42. M/G1, G1, G2/M, and S: genes with expression at peak at the corresponding stage of the cell cycle [42]
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