Papers In Press, published online ahead of print January 29, 2007
J. Biol. Chem, 10.1074/jbc.M611643200
Submitted on December 19, 2006
Revised on January 29, 2007
Accepted on January 29, 2007
Geminin cleavage during apoptosis by caspase-3 alters its binding ability to the SWI/SNF subunit Brahma
Vassilis Roukos, Maria S. Iliou, Hideo Nishitani, Marc Gentzel, Matthias Wilm, Stavros Taraviras, and Zoi Lygerou
Department of Biology, School of Medicine, Rio, Patras GR 26500
Corresponding Author: lygerou{at}med.upatras.gr
Geminin has been proposed to coordinate cell cycle and differentiation events through balanced interactions with the cell cycle regulator Cdt1 and with homeobox transcription factors and chromatin remodelling activities implicated in cell fate decisions. Here we show that Geminin is cleaved in primary cells and cancer cell lines induced to undergo apoptosis by a variety of stimuli. Geminin targeting is mediated by caspase-3 both in vivo and in vitro. Two sites at the carboxy-terminus of Geminin (named C1 and C2) are cleaved by the caspase, producing truncated forms of Geminin. We provide evidence that Geminin cleavage is regulated by phosphorylation. Casein kinase II alters Geminin cleavage at site C1 in vitro, while mutating phosphorylation competent Ser/Thr residues proximal to site C1 affects Geminin cleavage in vivo. We show that truncated Geminin produced by cleavage at C1 can promote apoptosis. In contrast, Geminin cleaved at site C2 has lost the ability to interact with Brahma (Brm), a catalytic subunit of the SWI/SNF chromatin remodelling complex, while binding efficiently to Cdt1, indicating that targeting of Geminin during apoptosis differentially affects interactions with its binding partners.