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© The Rockefeller University Press, 0021-9525/2003/12/929 $8.00
The Journal of Cell Biology, Volume 163, Number 5, 929-929

S is for sticky

Centromeres fall apart (right) without Hsk1 action in S phase. Forsburg/Macmillan

A kinase better known for triggering DNA replication also helps create the sticky heterochromatin at centromeres of fission yeast, according to Julie Bailis, Susan Forsburg (Salk Institute, La Jolla, CA), and colleagues.

The dual action makes sense, as chromosomes must be stuck together as soon as they are replicated. The responsible kinase activity, Hsk1 (CDC7)–Dfp1, is restricted to S phase, when DNA replication takes place.

Dfp1 turned up in a two-hybrid screen with Swi6, the fission yeast equivalent of heterochromatin protein 1 (HP1). Cells with a mutant Dfp1 that no longer binds Swi6 can replicate their DNA but suffer segregation errors when their defective centromeres fall apart. Swi6 localization is normal in these cells but, based on in vitro results, Swi6 phosphorylation may be reduced. This is the first indication that Swi6 localization is not sufficient to define heterochromatin function.

An interesting parallel is known in budding yeast, where establishment of silent heterochromatin at the mating type locus requires passage through S phase, though not DNA replication. Budding yeast lacks an HP1 homologue, but perhaps other proteins serve an equivalent heterochromatic function.

Reference:

Bailis, J.M., et al. 2003. Nat. Cell Biol. 10.1038/ncb1069.

William A. Wells

wellsw{at}rockefeller.edu

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This Article Full Text (PDF, 425K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Wells, W. A. Search for Related Content PubMed Articles by Wells, W. A. Social Bookmarking                            What's this?