| Autor: |
Paciotti, Vera, Clerici, Michela, Scotti, Maddalena, Lucchini, Giovanna, Longhese, Maria Pia |
| Zdroj: |
Molecular and Cellular Biology; June 2001, Vol. 21 Issue: 12 p3913-3925, 13p |
| Abstrakt: |
ABSTRACTDNA damage checkpoints lead to the inhibition of cell cycle progression following DNA damage. The Saccharomyces cerevisiaeMec1 checkpoint protein, a phosphatidylinositol kinase-related protein, is required for transient cell cycle arrest in response to DNA damage or DNA replication defects. We show thatmec1kinase-deficient (mec1kd) mutants are indistinguishable from mec1Δcells, indicating that the Mec1 conserved kinase domain is required for all known Mec1 functions, including cell viability and proper DNA damage response. Mec1kd variants maintain the ability to physically interact with both Ddc2 and wild-type Mec1 and cause dominant checkpoint defects when overproduced in MEC1cells, impairing the ability of cells to slow down S phase entry and progression after DNA damage in G1or during S phase. Conversely, an excess of Mec1kd inMEC1cells does not abrogate the G2/M checkpoint, suggesting that Mec1 functions required for response to aberrant DNA structures during specific cell cycle stages can be separable. In agreement with this hypothesis, we describe two new hypomorphic mec1mutants that are completely defective in the G1/S and intra-S DNA damage checkpoints but properly delay nuclear division after UV irradiation in G2. The finding that these mutants, although indistinguishable frommec1Δcells with respect to the ability to replicate a damaged DNA template, do not lose viability after UV light and methyl methanesulfonate treatment suggests that checkpoint impairments do not necessarily result in hypersensitivity to DNA-damaging agents. |
| Databáze: |
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