Recombinant cyclin B-Cdk1-Suc1 capable of multi-site mitotic phosphorylationin vitro

Abstract

Cyclin-dependent kinase 1 (Cdk1) complexed with cyclin B phosphorylates multiple sites on hundreds of proteins during mitosis. However, it is not fully understood how multi-site mitotic phosphorylation by cyclin B-Cdk1 controls the structures and functions of individual substrates. Here we develop an easy-to-use protocol to express recombinant vertebrate cyclin B and Cdk1 in insect cells from a single baculovirus vector and to purify their complexes with excellent homogeneity. A series of in-vitro assays demonstrate that the recombinant cyclin B-Cdk1 can efficiently and specifically phosphorylate the SP and TP motifs in substrates. The addition of Suc1 (a Cks1 homolog in fission yeast) accelerates multi-site phosphorylation of an artificial substrate containing TP motifs. Importantly, we show that mitosis-specific multi-subunit and multi-site phosphorylation of the condensin I complex can be recapitulated in vitro using recombinant cyclin B-Cdk1-Suc1. The materials and protocols described here will pave the way for dissecting the biochemical basis of critical mitotic processes that accompany Cdk1-mediated large-scale phosphorylation.

Regulation of condensin II by self-suppression and release mechanisms

“…Finally, we tested whether the D3 C-tail could be phosphorylated by recombinant cyclin B-Cdk1 (M-CDK) in vitro ( Shintomi et al. , 2023 ).…”

“…Expression and purification of Xenopus tropicalis cyclin B-Cdk1 (M-CDK) and Schizosaccharomyces pombe Suc1 were described by Shintomi et al. (2023) .…”