Previous Article | Next Article ![]()
Mol. Cell. Biol., Nov 1996, 6385-6397, Vol 16, No. 11
HH Lim, PY Goh and U Surana
In eukaryotes, mitosis requires the activation of cdc2 kinase via
association with cyclin B and dephosphorylation of the threonine 14 and
tyrosine 15 residues. It is known that in the budding yeast Saccharomyces
cerevisiae, a homologous kinase, Cdc28, mediates the progression through M
phase, but it is not clear what specific mitotic function its activation by
the dephosphorylation of an equivalent tyrosine (Tyr-19) serves. We report
here that cells expressing cdc28- E19 (in which Tyr-19 is replaced by
glutamic acid) perform Start- related functions, complete DNA synthesis,
and exhibit high levels of Clb2-associated kinase activity but are unable
to form bipolar spindles. The failure of these cells to form mitotic
spindles is due to their inability to segregate duplicated spindle pole
bodies (SPBs), a phenotype strikingly similar to that exhibited by a
previously reported mutant defective in both kinesin-like motor proteins
Cin8 and Kip1. We also find that the overexpression of SWE1, the
budding-yeast homolog of wee1, also leads to a failure to segregate SPBs.
These results imply that dephosphorylation of Tyr-19 is required for the
segregation of SPBs. The requirement of Tyr-19 dephosphorylation for
spindle assembly is also observed under conditions in which spindle
formation is independent of mitosis, suggesting that the involvement of
Cdc28/Clb kinase in SPB separation is direct. On the basis of these
results, we propose that one of the roles of Tyr-19 dephosphorylation is to
promote SPB separation.
Copyright © 1996, American Society for Microbiology
Spindle pole body separation in Saccharomyces cerevisiae requires dephosphorylation of the tyrosine 19 residue of Cdc28
Institute of Molecular and Cell Biology, National University of Singapore.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»