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  • The EMBO Journal (2006) 25, 1987 - 1996
  • doi:10.1038/sj.emboj.7601075

Published online: 13 April 2006

A CDK-catalysed regulatory phosphorylation for formation of the DNA replication complex Sld2–Dpb11

Yon-Soo Tak1,2,a, Yoshimi Tanaka1,3, Shizuko Endo1, Yoichiro Kamimura1,2,3,b and Hiroyuki Araki1,2,3

  1. Division of Microbial Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Shizuoka, Japan
  2. Department of Genetics, SOKENDAI, Mishima, Shizuoka, Japan
  3. CREST, Kawaguchi, Saitama, Japan

Correspondence to:

Hiroyuki Araki, Division of Microbial Genetics, National Institute of Genetics, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka 411-8540, Japan. Tel.: +81 55 981 6754; Fax: +81 55 981 6762; E-mail: hiaraki@lab.nig.ac.jp

aPresent address: Department of Biological Sciences, KAIST, Daejeon 305-701, Korea

bPresent address: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA

Received 8 November 2005; Accepted 9 March 2006

Phosphorylation often regulates protein–protein interactions to control biological reactions. The Sld2 and Dpb11 proteins of budding yeast form a phosphorylation-dependent complex that is essential for chromosomal DNA replication. The Sld2 protein has a cluster of 11 cyclin-dependent kinase (CDK) phosphorylation motifs (Ser/Thr–Pro), six of which match the canonical sequences Ser/Thr–Pro–X–Lys/Arg, Lys/Arg–Ser/Thr–Pro and Ser/Thr–Pro–Lys/Arg. Simultaneous alanine substitution for serine or threonine in all the canonical CDK-phosphorylation motifs severely reduces complex formation between Sld2 and Dpb11, and inhibits DNA replication. Here we show that phosphorylation of these canonical motifs does not play a direct role in complex formation, but rather regulates phosphorylation of another residue, Thr84. This constitutes a non-canonical CDK-phosphorylation motif within a 28-amino-acid sequence that is responsible, after phosphorylation, for binding of Sld2–Dpb11. We further suggest that CDK-catalysed phosphorylation of sites other than Thr84 renders Thr84 accessible to CDK. Finally, we argue that this novel mechanism sets a threshold of CDK activity for formation of the essential Sld2 to Dpb11 complex and therefore prevents premature DNA replication.

  • Keywords:

    • BRCT,
    • CDK,
    • DNA replication,
    • phosphorylation,
    • S phase