¹Laboratoire de Biologie Moléculaire de la Cellule, UMR5161 CNRS/ENS de Lyon, IFR 128 Biosciences Lyon Gerland, Lyon cedex 07, Rhone, France

Correspondence: Dr P Jalinot, Laboratoire de Biologie Moléculaire de la Cellule, UMR5161, CNRS/ENS de Lyon, 46 Allée d'Italie, Lyon cedex 07, Rhone 69364, France. E-mail: pjalinot@ens-lyon.fr

Received 27 October 2006; Revised 20 December 2006; Accepted 5 January 2007; Published online 19 February 2007.

Abstract

The mouse int6 gene is a frequent integration site of the mouse mammary tumor virus and INT6 silencing by RNA interference in HeLa cells causes an increased number of cells in the G2/M phases of the cell cycle, along with mitotic defects. In this report, we investigated the functional significance of the interaction between INT6 and MCM7, which was observed in a two-hybrid screen performed with INT6 as bait. It was found that proteasome inhibition strengthens interaction between both proteins and that INT6 stabilizes MCM7. Removal of MCM7 from chromatin as replication proceeds was accelerated in INT6-silenced cells and reduced amounts of protein were transiently observed, followed by a correction resulting from stimulation of mcm7 gene expression. Synchronized cells depleted for either INT6 or MCM7 display a reduction in thymidine incorporation and a reinforced association of RPA and claspin with chromatin. These data show that INT6 stabilizes chromatin-bound MCM7 and that alteration of this effect is associated with replication deficiency.