Chk1-dependent S-M checkpoint delay in vertebrate cells is linked to maintenance of viable replication structures

Zachos, G., Rainey, M. and Gillespie, D. (2005) Chk1-dependent S-M checkpoint delay in vertebrate cells is linked to maintenance of viable replication structures. Molecular and Cellular Biology, 25(2), pp. 563-574. (doi: 10.1128/MCB.25.2.563-574.2005)

Abstract

We investigated mitotic delay during replication arrest (the S-M checkpoint) in DT40 B-lymphoma cell: deficient in the Chk1 or Chk2 kinase. We show, here that cells lacking Chk1, but not those lacking Chk2, enter mitosis with incompletely replicated DNA when DNA synthesis is blocked, but only after an initial delay. This initial delay persists when SM checkpoint failure is induced in Chk2(-/-) cells with the Chk1 inhibitor UCN(.)01. indicating that it does not depend on Chk1 or Chk2 activity. Surprisingly, dephosphorylation of tyrosine 15 did not accompany Cdc2 activation during premature entry to mitosis in Chk1(-/-) cells, although mitotic phosphorylation of cyclin B-2 did occur. Previous studies have shown that Chk1 is required to stabilize stalled replication forks during replication arrest, and strikingly, premature mitosis occurs only in Chk1-deficient cells which have lost the capacity to synthesize DNA as a result of progressive replication fork inactivation. These results suggest that Chk1 maintains the S-M checkpoint indirectly by preserving the viability of replication structures and that it is the continued presence of such structures. rather than the activation of Chk1 per se, which delays mitosis until DNA replication is complete.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gillespie, Professor David
• Authors: Zachos, G., Rainey, M., and Gillespie, D.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Journal Name: Molecular and Cellular Biology
• ISSN: 0270-7306