Publications by authors named "I I Ouspenski"

Condensins I and II in vertebrates are essential ATP-dependent complexes necessary for chromosome condensation in mitosis. Condensins depletion is known to perturb structure and function of centromeres, however the mechanism of this functional link remains elusive. Depletion of condensin activity is now shown to result in a significant loss of loading of CENP-A, the histone H3 variant found at active centromeres and the proposed epigenetic mark of centromere identity.

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The condensin complex is essential for sister chromatid segregation in eukaryotic mitosis. Nevertheless, in budding yeast, condensin mutations result in massive mis-segregation of chromosomes containing the nucleolar organizer, while other chromosomes, which also contain condensin binding sites, remain genetically stable. To investigate this phenomenon we analyzed the mechanism of the cell-cycle arrest elicited by condensin mutations.

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Pit-1, a POU-class nuclear DNA-binding transcription factor, specifies three of the parenchymal cell types in anterior pituitary ontogeny. Using fluorescent fusions and live cell imaging, we have compared the dynamic behavior of wild-type and inactivating Pit-1 point mutations. Fluorescence recovery after photobleaching (FRAP) and real-time extraction data indicate that wild-type Pit-1 has a dynamic mobility profile, with t(1/2s) approximately 5-7 s when expressed from low to high amounts, respectively.

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Background: Transformation-associated recombination (TAR) cloning in yeast is a unique method for selective isolation of large chromosomal fragments or entire genes from complex genomes. The technique involves homologous recombination, during yeast spheroplast transformation, between genomic DNA and a TAR vector that has short (approximately 60 bp) 5' and 3' gene targeting sequences (hooks).

Result: TAR cloning requires that the cloned DNA fragment carry at least one autonomously replicating sequence (ARS) that can function as the origin of replication in yeast, which prevents wide application of the method.

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A centromere-specific variant of histone H3, centromere protein A (CENP-A), is a critical determinant of centromeric chromatin, and its location on the chromosome may determine centromere identity. To search for factors that direct CENP-A deposition at a specific chromosomal locus, we took advantage of the observation that CENP-A, when expressed at elevated levels, can get incorporated at ectopic sites on the chromosome, in addition to the centromere. As core histone hypoacetylation and DNA replication timing have been implicated as epigenetic factors that may be important for centromere identity, we hypothesized that the sites of preferential CENP-A deposition will be distinguished by these parameters.

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