Assembly of Drosophila centromeric chromatin proteins during mitosis

PLoS Genet. 2011 May;7(5):e1002068. doi: 10.1371/journal.pgen.1002068. Epub 2011 May 12.

Abstract

Semi-conservative segregation of nucleosomes to sister chromatids during DNA replication creates gaps that must be filled by new nucleosome assembly. We analyzed the cell-cycle timing of centromeric chromatin assembly in Drosophila, which contains the H3 variant CID (CENP-A in humans), as well as CENP-C and CAL1, which are required for CID localization. Pulse-chase experiments show that CID and CENP-C levels decrease by 50% at each cell division, as predicted for semi-conservative segregation and inheritance, whereas CAL1 displays higher turnover. Quench-chase-pulse experiments demonstrate that there is a significant lag between replication and replenishment of centromeric chromatin. Surprisingly, new CID is recruited to centromeres in metaphase, by a mechanism that does not require an intact mitotic spindle, but does require proteasome activity. Interestingly, new CAL1 is recruited to centromeres before CID in prophase. Furthermore, CAL1, but not CENP-C, is found in complex with pre-nucleosomal CID. Finally, CENP-C displays yet a different pattern of incorporation, during both interphase and mitosis. The unusual timing of CID recruitment and unique dynamics of CAL1 identify a distinct centromere assembly pathway in Drosophila and suggest that CAL1 is a key regulator of centromere propagation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Centromere*
  • Chromatin / metabolism*
  • Cyclin A / metabolism
  • Drosophila
  • Humans
  • Metaphase
  • Microtubules / metabolism
  • Mitosis*
  • Prophase
  • Proteasome Endopeptidase Complex / metabolism

Substances

  • Chromatin
  • Cyclin A
  • Proteasome Endopeptidase Complex