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The CK2 phosphorylation of catalytic domain of Cdc34 modulates its activity at the G1 to S transition in Saccharomyces cerevisiae

Volume 7, Issue 10   May 15, 2008
Pages 1391 - 1401
http://dx.doi.org/10.4161/cc.7.10.5825
Authors: Paola Coccetti, Farida Tripodi, Gabriella Tedeschi, Simona Nonnis, Oriano Marin, Sonia Fantinato, Claudia Cirulli, Marco Vanoni and Lilia Alberghina

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Abstract:
The ubiquitin-conjugating enzyme Cdc34 was recently shown to be phosphorylated by CK2 on the C-terminal tail. Here we present novel findings indicating that in budding yeast CK2 phosphorylates Cdc34 within the N-terminal catalytic domain. Specifically, we show, by direct mass spectrometry analysis, that Cdc34 is phosphorylated in vitro and in vivo by CK2 on Ser130 and Ser167, and that the phosphoserines 130 and 167 are not present after CK2 inactivation in a cka1Δcka2-8ts strain. CK2 phosphorylation of Ser130 and Ser167 strongly stimulates Cdc34 ubiquitin charging in vitro. The Cdc34S130AS167A mutant shows a basal ubiquitin charging activity which is indistinguishable from that of wild type but is not activated by CK2 phosphorylation and its expression fails to complement a cdc34-2ts yeast strain, supporting a model in which activation of Cdc34 involves CK2-mediated phosphorylation of its catalytic domain.

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