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The essential function of Swc4p - a protein shared by two chromatin-modifying complexes of the yeast Saccharomyces cerevisiae - resides within its N-terminal part

100%
Miciałkiewicz A., Chełstowska A.
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2008
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vol. 55
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issue 3
603-612
EN
The Swc4p protein, encoded by an essential gene, is shared by two chromatin-remodeling complexes in Saccharomyces cerevisiae cells: NuA4 (nucleosome acetyltransferase of H4) and SWR1. The SWR1 complex catalyzes ATP-dependent exchange of the nucleosomal histone H2A for H2AZ (Htz1p). The activity of NuA4 is responsible mainly for the acetylation of the H4 histone but also for the acetylation of H2A and H2AZ. In this work we investigated the role of the Swc4p protein. Using random mutagenesis we isolated a collection of swc4 mutants and showed that the essential function of Swc4p resides in its N-terminal part, within the first 269 amino acids of the 476-amino acid-long protein. We also demonstrated that Swc4p is able to accommodate numerous mutations without losing its functionality under standard growth conditions. However, when swc4 mutants were exposed to methyl methanesulfonate (MMS), hydroxyurea or benomyl, severe growth deficiencies appeared, pointing to an involvement of Swc4p in many chromatin-based processes. The mutants' phenotypes did not result from an impairment of histone acetylation, as in the mutant which bears the shortest isolated variant of truncated Swc4p, the level of overall H4 acetylation was unchanged.
2
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Suppressors of translation initiation defect in hem12 locus of Saccharomyces cerevisiae.

81%
Góra M., Pluta K., Chełstowska A., Żołądek T.
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2000
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vol. 47
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issue 1
181-190
EN
A system for the positive selection of transational initiation suppressors in S. cerevisiae has been developed. A mutant with an ATA initiation codon in the HEM12 gene, encoding uroporphyrinogen decarboxylase, was used to select cis- and trans-acting suppressors. These suppressors partially restore growth on nonfermentable carbon sources, such as glycerol, but still allow the accumulation of porphyrins. All extragenic suppressors are mapped to the SUI1 locus, encoding initiation factor eIF1. The effect of the hem12 mutation is also partially reversed by the known SUI3 suppressor encoding the β subunit of eIF2. In contrast, the sui2 suppressor encoding the α subunit of eIF2 does not affect the hem 12 phenotype. The intragenic suppressors are able to restore the translation of hem12 due to the generation of additional, in frame AUG codons upstream of the hem12-14 mutation. Mutational analysis of the HEM12 leader sequence was also performed to determine the role of small open reading frames (uORFs) present upstream of the HEM12 ORF. Studies on the expression of integrated hem12-1/4-lacZ fusion, devoid of all upstream ATGs, indicate a lack of regulatory effect of uORFs on HEM12 translation.
3
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Cohesin Irr1/Scc3 is likely to influence transcription in Saccharomyces cerevisiae via interaction with Mediator complex

61%
Cena A., Skoneczny M., Chełstowska A., Kowalec P., Natorff R., Kurlandzka A.
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2013
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vol. 60
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issue 2
233-238
EN
The evolutionarily conserved proteins forming sister chromatid cohesion complex are also involved in the regulation of gene transcription. The participation of SA2p (mammalian ortholog of yeast Irr1p, associated with the core of the complex) in the regulation of transcription is already described. Here we analyzed microarray profiles of gene expression of a Saccharomyces cerevisiae irr1-1/IRR1 heterozygous diploid strain. We report that expression of 33 genes is affected by the presence of the mutated Irr1-1p and identify those genes. This supports the suggested role of Irr1p in the regulation of transcription. We also indicate that Irr1p may interact with elements of transcriptional coactivator Mediator.
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