Development of an enzymatic DNA repair assay for molecular epidemiology studies: distribution of OGG activity in healthy individuals.
While the role of reduced DNA repair in susceptibility to hereditary cancers is well established, its role in sporadic cancer is less understood. One of the reasons is the lack of specific DNA repair assays that are suitable for epidemiology studies. Here we describe the development of the OGG test, an epidemiology-grade enzymatic assay for the activity of the base excision repair enzyme 8-oxoguanine DNA glycosylase, in protein extracts prepared from human blood cells. The assay is robust and reproducible, with a coefficient of variation of 10%. Using the OGG test we determined OGG activity in 120 healthy individuals. Our results show an inter-individual variation of 2.8-fold in OGG activity, from 3.6 up to 10.1units/microg protein, with a mean value of 7.2units/microg protein. There was no significant difference in OGG activity between males and females, or between smokers and non-smokers. Interestingly, there was a gender-specific effect of age: OGG activity was slightly but significantly lower in males older than the age of 55 years compared to younger males, but not in females at the same age groups. Analysis of OGG1 mRNA by quantitative real-time RT-PCR showed a group trend of an increase in OGG enzymatic activity with increasing mRNA expression, but the correlation between activity and mRNA in individuals was poor, indicating the importance of factors other than mRNA expression. The OGG test described is expected to be useful in studying the role of 8-oxoguanine repair in cancer, as recently demonstrated for non-small cell lung cancer [T. Paz-Elizur, M. Krupsky, S. Blumenstein, D. Elinger, E. Schechtman, Z. Livneh, J. Natl. Cancer Inst. 95 (2003) 1312-1319]. In addition, it may serve as a paradigm for the development of additional functional DNA repair tests, which are needed in order to gain further insight into the role of DNA repair in cancer risk and pathology.
Paz-Elizur
Tamar
T
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Elinger
Dalia
D
Leitner-Dagan
Yael
Y
Blumenstein
Sara
S
Krupsky
Meir
M
Berrebi
Alain
A
Schechtman
Edna
E
Livneh
Zvi
Z
D001681:Biological Assay; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000453:epidemiology / Q000235:genetics*; D045647:DNA Glycosylases / Q000097:blood / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D004260:DNA Repair; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000453:epidemiology / Q000235:genetics; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D012333:RNA, Messenger; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human