![]() ![]() 2000), the CENP-A targeting domain (CATD) within the HFD, essential N- and C-termini ( Black et al. These include the Histone Fold Domain and the essential N-terminus (END) in Cse4 ( Keith et al. For Cse4 and CENP-A, the ability to swap centromere-specific domains with canonical Histone H3 reveals crucial molecular determinants unique to the centromere nucleosome. At the heart of such controversies is the quest to determine critical features responsible for establishing a functional kinetochore. 2014), there is controversy over the number of Cse4 molecules and the handedness of DNA wrap. In budding yeast, with its point centromere and purportedly single Cse4-containing nucleosome ( Lawrimore et al. 2013), right-handed hemisomes or octamers ( Furuyama and Henikoff 2009 Diaz-Ingelmo et al. 2013) canonical left-handed octamers ( Dechassa et al. A variety of studies reveal that CENP-A containing nucleoprotein complexes can adopt a number of conformations, including tetramers ( Dalal et al. The functional role of CENP-A at the centromere is considerably less clear. Centromere-Specific Histone H3 Variant, Cse4 Yeast, CENP-A MammalsĬentromeres contain an atypical Histone H3, known as CENP-A, or Cse4 in budding yeast ( Earnshaw et al. We will focus on the conserved features of centromere in this review.ġ.1. Recently, centromeric chromatin has been reconstituted in vitro using alpha satellite DNA revealing unexpected features of centromeric DNA organization, replication, and response to stress. Thus, centromeres of different organisms differ in how they specify kinetochore assembly, but there may be important centromere chromatin functions that are conserved throughout phylogeny. In both organisms the sister kinetochores are separated by about 1 µm. In mammals, 5–10 Mb lies between sister kinetochores. In yeast the 16 chromosomes are clustered into a 250 nm diameter region, and 800 kb (16 × 50 kb) or ⁓1 Mb of DNA lies between sister kinetochores. However in both yeast and mammals, the total amount of DNA between the sites of microtubule attachment in metaphase is highly conserved. The chromatin sites that directly interface to microtubules cannot be identified due to the repeated sequence within the mammalian centromere. This is typically called centromere chromatin. The remainder of the centromere lies between the sister kinetochores. The kinetochore interacts with a very small fraction of DNA on the surface of the centromeric region. In mammals, a 5–10 Mb region dictates where the kinetochore is built. We refer to the flanking chromatin as the pericentromere in yeast. The enrichment spans about 30–50 kb around each centromere. The flanking region is enriched (3X) in cohesin and condensin relative to the remaining chromosome arms. In budding yeast the 125 bp point centromere is sufficient to specify kinetochore assembly. The pericentromere is the physical region responsible for the geometry of bi-oriented sister kinetochores in metaphase. The centromere is the genetic locus that specifies the site of kinetochore assembly, where the chromosome will attach to the kinetochore microtubule. ![]()
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