Related Experiment Video
Updated: Jun 27, 2026
Protocol for Acute and Chronic Ecotoxicity Testing of the Turquoise Killifish Nothobranchius furzeri
Published on: April 24, 2018
Characterization of rainbow trout CHK2 and its potential as a genotoxicity biomarker
Jessica D Steinmoeller1, Kazuhiro Fujiki, Aman Arya
1Department of Biology, University of Waterloo, Waterloo, Ontario, Canada.
Abstract:
Checkpoint kinase 2 (CHK2) plays a central and conserved role in the eukaryotic DNA damage response. Few cell cycle checkpoint proteins have been examined in aquatic organisms, and this study is the first to characterize CHK2 expression in a fish species. CHK2 was cloned from Oncorhynchus mykiss, the rainbow trout. The coding region extends over 5741 nucleotides in the genome, including 13 introns, and specifies a predicted 533 amino acid protein. Southern blot analysis revealed that CHK2 exists as a single copy in the rainbow trout genome. Recombinant protein representing the FHA domain was used to generate polyclonal anti-CHK2 antibodies. While CHK2 transcript levels were relatively low in gill and high in brain, the opposite was true for protein levels. Both gill and brain cell cultures were treated with bleomycin, which induces double-strand DNA breaks. There was no effect on levels of CHK2 in gill cells, suggesting that the protein is constitutively active in this tissue. In contrast, brain cells upregulated CHK2 in a dose-dependent manner. The tissue specific expression of CHK2 and its ability to respond to bleomycin treatment suggests that some checkpoint proteins may serve as suitable biomarkers for DNA damage in rainbow trout and other fish species.
Insights
Checkpoint kinase 2 (CHK2) is crucial for DNA repair in rainbow trout. Its expression varies by tissue, with brain CHK2 levels increasing after DNA damage, suggesting biomarker potential.
Area of Science:
- Molecular biology
- Genomics
- Biochemistry
Background:
- Checkpoint kinase 2 (CHK2) is a key protein in the eukaryotic DNA damage response.
- Understanding CHK2 in aquatic organisms is limited, with no prior studies in fish.
Purpose of the Study:
- To characterize the expression and regulation of CHK2 in rainbow trout (Oncorhynchus mykiss).
- To investigate CHK2's potential as a biomarker for DNA damage in fish.
Main Methods:
- Cloning and sequencing of CHK2 from rainbow trout.
- Southern blot analysis to determine gene copy number.
- Antibody generation against the CHK2 FHA domain.
- Analysis of CHK2 transcript and protein levels in different tissues (gill, brain).
- Treatment of cell cultures with bleomycin to induce DNA damage and assess CHK2 response.
Main Results:
- The rainbow trout CHK2 gene spans 5741 nucleotides with 13 introns, encoding a 533 amino acid protein.
- CHK2 is present as a single copy in the rainbow trout genome.
- Tissue-specific expression: low CHK2 transcript in gills, high in brain; conversely, high protein in gills, low in brain.
- Gill cells showed no change in CHK2 levels after bleomycin treatment, indicating constitutive activity.
- Brain cells exhibited a dose-dependent upregulation of CHK2 following bleomycin exposure.
Conclusions:
- Tissue-specific expression and differential regulation of CHK2 in rainbow trout suggest specialized roles.
- Upregulation of CHK2 in brain cells in response to DNA damage highlights its potential as a biomarker for genotoxicity in fish.
- This study provides foundational knowledge for using CHK2 as a biomarker in aquatic species.
