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Human SAD1 kinase is involved in UV-induced DNA damage checkpoint function
Rui Lu1, Hiroyuki Niida, Makoto Nakanishi
1Department of Biochemistry and Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.
The Journal of Biological Chemistry
|May 20, 2004
Summary
Researchers identified human SAD1 (hsSAD1), a novel kinase involved in the G(2) DNA damage checkpoint. This discovery suggests an alternative pathway to the known ataxia-telangiectasia-mutated (ATM) and Rad3-related (ATR)-Chk1 pathways, expanding our understanding of cell cycle regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- DNA damage triggers cell cycle checkpoints, notably the G(2) checkpoint, to prevent mitotic entry.
- Existing G(2) arrest pathways involve p38MAPK and ATM/ATR-Chk1 signaling, but other regulators may exist.
Purpose of the Study:
- To identify novel signaling pathways involved in the G(2) DNA damage checkpoint.
- To characterize the function and regulation of a newly identified kinase, human SAD1 (hsSAD1).
Main Methods:
- Bioinformatic search for homologous proteins to known cell cycle regulators.
- In vitro kinase assays and in vivo phosphorylation studies.
- Analysis of hsSAD1 expression, localization, and functional role in G(2)/M arrest using overexpression and small interfering RNA (siRNA).
Main Results:
- Human SAD1 (hsSAD1) was identified, showing homology to known mitosis-regulatory kinases.
- hsSAD1 phosphorylates key cell cycle regulators: Wee1A, Cdc25-C, and Cdc25-B.
- DNA damage (UV, MMS) enhanced hsSAD1 kinase activity and nuclear translocation, inducing G(2)/M arrest, which was partially dependent on hsSAD1 levels.
Conclusions:
- hsSAD1 functions as a DNA damage checkpoint kinase, particularly in response to UV and methyl methane sulfonate (MMS) induced damage.
- The findings indicate the existence of an alternative G(2) DNA damage checkpoint pathway independent of ATR-Chk1 and p38MAPK.