Evaluation of intra- and interspecific divergence of satellite DNA sequences by nucleotide frequency calculation and pairwise sequence comparison

Satellite DNA sequences are known to be highly variable and to have been subjected to concerted evolution that homogenizes member sequences within species. We have analyzed the mode of evolution of satellite DNA sequences in four fishes from the genus Diplodus by calculating the nucleotide frequency of the sequence array and the phylogenetic distances between member sequences. Calculation of nucleotide frequency and pairwise sequence comparison enabled us to characterize the divergence among member sequences in this satellite DNA family. The results suggest that the evolutionary rate of satellite DNA in D. bellottii is about two-fold greater than the average of the other three fishes, and that the sequence homogenization event occurred in D. puntazzo more recently than in the others. The procedures described here are effective to characterize mode of evolution of satellite DNA

Quantitative Microscopy Reveals Centromeric Chromatin Stability, Size, and Cell Cycle Mechanisms to Maintain Centromere Homeostasis

The deposited item is a book chapter and is part of the series "Centromeres and Kinetochores" published by the publisher Springer Verlag. The deposited book chapter is a post-print version and has been submitted to peer reviewing. There is no public supplementary material available for this publication. This publication hasn't any creative commons license associated.Centromeres are chromatin domains specified by nucleosomes containing the histone H3 variant, CENP-A. This unique centromeric structure is at the heart of a strong self-templating epigenetic mechanism that renders centromeres heritable. We review how specific quantitative microscopy approaches have contributed to the determination of the copy number, architecture, size, and dynamics of centromeric chromatin and its associated centromere complex and kinetochore. These efforts revealed that the key to long-term centromere maintenance is the slow turnover of CENP-A nucleosomes, a critical size of the chromatin domain and its cell cycle-coupled replication. These features come together to maintain homeostasis of a chromatin locus that directs its own epigenetic inheritance and facilitates the assembly of the mitotic kinetochore.There are no funders and sponsors indicated explicitly in the document.info:eu-repo/semantics/publishedVersio

Molecular architecture of a kinetochore–microtubule attachment site

Kinetochore attachment to spindle microtubule plus-ends is necessary for accurate chromosome segregation during cell division in all eukaryotes. The centromeric DNA of each chromosome is linked to microtubule plus-ends by eight structural-protein complexes1–9. Knowing the copy number of each of these complexes at one kinetochore–microtubule attachment site is necessary to understand the molecular architecture of the complex, and to elucidate the mechanisms underlying kinetochore function. We have counted, with molecular accuracy, the number of structural protein complexes in a single kinetochore–microtubule attachment using quantitative fluorescence microscopy of GFP-tagged kinetochore proteins in the budding yeast Saccharomyces cerevisiae. We find that relative to the two Cse4p molecules in the centromeric histone1, the copy number ranges from one or two for inner kinetochore proteins such as Mif2p2, to 16 for the DAM–DASH complex8,9 at the kinetochore–microtubule interface. These counts allow us to visualize the overall arrangement of a kinetochore–microtubule attachment. As most of the budding yeast kinetochore proteins have homologues in higher eukaryotes, including humans, this molecular arrangement is likely to be replicated in more complex kinetochores that have multiple microtubule attachments