The budding yeast Dbf2 protein kinase localises to the centrosome and moves to the bud neck in late mitosis

Dbf2 is a multifunctional protein kinase in Saccharomyces cerevisiae that f unctions in transcription, the stress response and as part of a network of genes in exit from mitosis, By analogy with fission yeast it seemed likely that these mitotic exit genes would be involved in cytokinesis. As a prelim inary investigation of this we have used Dbf2 tagged with GFP to examine in tracellular localisation of the protein in living cells. Dbf2 is found on t he centrosomes/spindle pole bodies (SPBs) and also at the bud neck where it forms a double ring. The localisation of Dbf2 is cell cycle regulated. it is on the SPBs for much of the cell cycle and migrates from there to the bu d neck in late mitosis, consistent with a role in cytokinesis. Dbf2 partly co-localises with septins at the bud neck. A temperature-sensitive mutant o f dbf2 also blocks progression of cytokinesis at 37 degreesC, Following cyt okinesis some Dbf2 moves into the nascent bud. Localisation to the bud neck depends upon the septins and also the mitotic exit network proteins Mob1, Cdc5, Cdc14 and Cdc15, The above data are consistent with Dbf2 acting downs tream in a pathway controlling cytokinesis.