Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published June 19, 2001 | Published
Journal Article Open

Protein kinase Cdc15 activates the Dbf2-Mob1 kinase complex


Exit from mitosis in budding yeast requires inactivation of cyclin-dependent kinases through mechanisms triggered by the protein phosphatase Cdc14. Cdc14 activity, in turn, is regulated by a group of proteins, the mitotic exit network (MEN), which includes Lte1, Tem1, Cdc5, Cdc15, Dbf2/Dbf20, and Mob1. The direct biochemical interactions between the components of the MEN remain largely unresolved. Here, we investigate the mechanisms that underlie activation of the protein kinase Dbf2. Dbf2 kinase activity depended on Tem1, Cdc15, and Mob1 in vivo. In vitro, recombinant protein kinase Cdc15 activated recombinant Dbf2, but only when Dbf2 was bound to Mob1. Conserved phosphorylation sites Ser-374 and Thr-544 (present in the human, Caenorhabditis elegans, and Drosophila melanogaster relatives of Dbf2) were required for DBF2 function in vivo, and activation of Dbf2-Mob1 by Cdc15 in vitro. Although Cdc15 phosphorylated Dbf2, Dbf2-Mob1, and Dbf2(5374A/T544A)-Mob1, the pattern of phosphate incorporation into Dbf2 was substantially altered by either the S374A T544A mutations or omission of Mob1. Thus, Cdc15 promotes the exit from mitosis by directly switching on the kinase activity of Dbf2. We propose that Mob1 promotes this activation process by enabling Cdc15 to phosphorylate the critical Ser-374 and Thr-544 phosphoacceptor sites of Dbf2.

Additional Information

© 2001 by the National Academy of Sciences. Edited by Tim Hunt, Imperial Cancer Research Fund, Hertfordshire, United Kingdom, and approved May 1, 2001 (received for review February 27, 2001). This paper was submitted directly (Track II) to the PNAS office. Published online before print June 12, 2001, 10.1073/pnas.141098998 We thank C. L. Denis and F. Luca for plasmids. We are particularly indebted to S. L. Jaspersen and D. O. Morgan for unpublished Cdc15 and Cdc15(K54L) baculoviruses. A.S.M. thanks W. Shou for her insight and encouragement, R. Azzam for helpful discussions, and R. Verma for help with peptide mapping. This work was supported by a grant from the National Institutes of Health (GM59940) and a Beckman Young Investigator Award (to R.J.D.). A.S.M. and R.J.D. are supported by the Howard Hughes Medical Institute. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Attached Files

Published - MAHpnas01.pdf


Files (248.8 kB)
Name Size Download all
248.8 kB Preview Download

Additional details

August 21, 2023
October 13, 2023