Chromatin structure of altered yeast centromeres. |
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| Authors: | M Saunders M Fitzgerald-Hayes K Bloom |
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| Affiliation: | Department of Biology, University of North Carolina, Chapel Hill 27514. |
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| Abstract: | We have investigated the chromatin structure of wild-type and mutationally altered centromere sequences in the yeast Saccharomyces cerevisiae by using an indirect end-labeling mapping strategy. Wild-type centromere DNA from chromosome III (CEN3) exhibits a nuclease-resistant chromatin structure 220-250 base pairs long, centered around the conserved centromere DNA element (CDE) III. A point mutation in CDE III that changes a central cytidine to a thymidine and completely disrupts centromere function has lost the chromatin conformation typically associated with the wild-type centromere. A second conserved DNA element, CDE I, is spatially separated from CDE III by 78-86 A + T-rich base pairs, which is termed CDE II. The sequence and spatial requirements for CDE II are less stringent; alterations in CDE II length and sequence can be tolerated to a limited extent. Nuclease-resistant cores are altered in dimension in two CDE II CEN3 mutations. Two CDE I deletion mutations that retain partial centromere function also show nuclease-resistant regions of reduced size and intensity. The results from a number of such altered centromeres indicate a correlation between the presence of a protected core and centromere function. |
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