Mol Cell Biol, April 1998, p. 2100-2107, Vol. 18, No. 4
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 038241; Division of Yeast Genetics, National Institute for Medical Research, London NW7 1AA, United Kingdom2; and Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309-03473
Received 6 October 1997/Returned for modification 19 November 1997/Accepted 23 January 1998
The DBF2 gene of the budding yeast Saccharomyces cerevisiae encodes a cell cycle-regulated protein kinase that plays an important role in the telophase/G1 transition. As a component of the multisubunit CCR4 transcriptional complex, DBF2 is also involved in the regulation of gene expression. We have found that MOB1, an essential protein required for a late mitotic event in the cell cycle, genetically and physically interacts with DBF2. DBF2 binds MOB1 in vivo and can bind it in vitro in the absence of other yeast proteins. We found that the expression of MOB1 is also cell cycle regulated, its expression peaking slightly before that of DBF2 at the G2/M boundary. While overexpression of DBF2 suppressed phenotypes associated with mob1 temperature-sensitive alleles, it could not suppress a mob1 deletion. In contrast, overexpression of MOB1 suppressed phenotypes associated with a dbf2-deleted strain and suppressed the lethality associated with a dbf2 dbf20 double deletion. A mob1 temperature-sensitive allele with a dbf2 disruption was also found to be synthetically lethal. These results are consistent with DBF2 acting through MOB1 and aiding in its function. Moreover, the ability of temperature-sensitive mutated versions of the MOB1 protein to interact with DBF2 was severely reduced, confirming that binding of DBF2 to MOB1 is required for a late mitotic event. While MOB1 and DBF2 were found to be capable of physically associating in a complex that did not include CCR4, MOB1 did interact with other components of the CCR4 transcriptional complex. We discuss models concerning the role of DBF2 and MOB1 in controlling the telophase/G1 transition.
Publication 1976 of the New Hampshire Agricultural Experiment
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