RRC ID 6649
Author Garcia MX, Foote C, van Es S, Devreotes PN, Alexander S, Alexander H.
Title Differential developmental expression and cell type specificity of Dictyostelium catalases and their response to oxidative stress and UV-light.
Journal Biochim Biophys Acta
Abstract Cells of Dictyostelium discoideum are highly resistant to DNA damaging agents such as UV-light, gamma-radiation and chemicals. The genes encoding nucleotide excision repair (NER) and base excision repair (BER) enzymes are rapidly upregulated in response to UV-irradiation and DNA-damaging chemicals, suggesting that this is at least partially responsible for the resistance of this organism to these agents. Although Dictyostelium is also unusually resistant to high concentrations of H(2)O(2), little is known about the response of this organism to oxidative stress. To determine if transcriptional upregulation is a common mechanism for responding to DNA-damaging agents, we have studied the Dictyostelium catalase and Cu/Zn superoxide dismutase antioxidant enzymes. We show that there are two catalase genes and that each is differentially regulated both temporally and spatially during multicellular development. The catA gene is expressed throughout growth and development and its corresponding enzyme is maintained at a steady level. In contrast, the catB gene encodes a larger protein and is only expressed during the final stages of morphogenesis. Cell type fractionation showed that the CatB enzyme is exclusively localized to the prespore cells and the CatA enzyme is found exclusively in the prestalk cells. Each enzyme has a different subcellular localization. The unique developmental timing and cell type distribution suggest that the role for catB in cell differentiation is to protect the dormant spores from oxidative damage. We found that exposure to H(2)O(2) does not result in the induction of the catalase, superoxide dismutase, NER or BER mRNAs. A mutant with greatly reduced levels of catA mRNA and enzyme has greatly increased sensitivity to H(2)O(2) but normal sensitivity to UV. These results indicate that the natural resistance to oxidative stress is not due to an ability to rapidly raise the level of antioxidant or DNA repair enzymes and that the response to UV-light is independent from the response to reactive oxygen compounds.
Volume 1492(2-3)
Pages 295-310
Published 2000-7-24
DOI 10.1016/s0167-4781(00)00063-4
PII S0167-4781(00)00063-4
PMID 11004503
MeSH Amino Acid Sequence Animals Bacterial Proteins / metabolism Catalase / genetics Catalase / metabolism* DNA Repair / genetics Dictyostelium / enzymology Dictyostelium / genetics Dictyostelium / physiology* Dictyostelium / radiation effects Gene Expression Regulation, Developmental* Genes, Protozoan / physiology Hydrogen Peroxide / pharmacology Molecular Sequence Data Oligopeptides Oxidative Stress / physiology* Sequence Homology, Amino Acid Subcellular Fractions Superoxide Dismutase / metabolism Ultraviolet Rays*
IF 3.411
Times Cited 31
Cellular slime molds G00022 G03221