Cyclin E Is Stabilized in Response to Replication Fork Barriers Leading to Prolonged S Phase Arrest

Xiaoyan Lu,Jia Liu,Randy J Legerski

doi:10.1074/jbc.m109.035949

Xiaoyan Lu, Jia Liu + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m109.035949

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Abstract

Cyclin E is a regulator of cyclin-dependent protein kinases (Cdks) and is involved in mediating the cell cycle transition from G(1) to S phase. Here, we describe a novel function for cyclin E in the long term maintenance of checkpoint arrest in response to replication barriers. Exposure of cells to mitomycin C or UV irradiation, but not ionizing radiation, induces stabilization of cyclin E. Stabilization of cyclin E reduces the activity of Cdk2-cyclin A, resulting in a slowing of S phase progression and arrest. In addition, cyclin E is shown to be required for stabilization of Cdc6, which is required for activation of Chk1 and the replication checkpoint pathway. Furthermore, the stabilization of cyclin E in response to replication fork barriers depends on ATR, but not Nbs1 or Chk1. These results indicate that in addition to its well studied role in promoting cell cycle progression, cyclin E also has a role in regulating cell cycle arrest in response to DNA damage.

Highlights

Modification inhibits ubiquitylation and subsequent degradation of Cdc6 by the anaphase-promoting complex (APC)/cyclosome, thereby promoting pre-RC assembly
These findings suggested the possibility that stabilization of cyclin E may mediate a long term arrest in the S phase of the cell cycle in response to replication stress
Our findings described here demonstrate that in response to DNA damage, such as introduced by MMC or UV irradiation, cyclin E is stabilized by a mechanism that reduces its level of ubiquitylation and ultimate degradation

Summary

Cyclin E Mediates Long Term Cell Cycle Arrest

We show that in response to the cross-linking drug mitomycin C (MMC) or UV irradiation, but not to IR, cyclin E is strongly stabilized during S phase. This stabilization of cyclin E interferes with the activation of Cdk2-cyclin A and impedes DNA synthesis and S phase progression. Cyclin E is required for the stabilization of Cdc, which has been shown previously to be required for the activation of Chk (38 – 41). These findings suggest that ATR-mediated stabilization of cyclin E represents a novel mechanism that induces a sustained arrest in response to fork-blocking lesions

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