Highly efficient base excision repair (BER) in human and rat male germ cells.
The quality of germ cell DNA is critical for the fate of the offspring, yet there is limited knowledge of the DNA repair capabilities of such cells. One of the main DNA repair pathways is base excision repair (BER) which is initiated by DNA glycosylases that excise damaged bases, followed by incision of the generated abasic (AP) sites. We have studied human and rat methylpurine-DNA glycosylase (MPG), uracil-DNA glycosylase (UNG), and the major AP endonuclease (HAP1/APEX) in male germ cells. Enzymatic activities and western analyses indicate that these enzymes are present in human and rat male germ cells in amounts that are at least as high as in somatic cells. Minor differences were observed between different cellular stages of rat spermatogenesis and spermiogenesis. Repair of methylated DNA was also studied at the cellular level using the Comet assay. The repair was highly efficient in both human and rat male germ cells, in primary spermatocytes as well as round spermatids, compared to rat mononuclear blood cells or hepatocytes. This efficient BER removes frequently occurring DNA lesions that arise spontaneously or via environmental agents, thereby minimising the number of potential mutations transferred to the next generation.
Olsen
A K
AK
Section for Product Toxicology, Department of Environmental Medicine, National Institute of Public Health, PO Box 4404 Nydalen, N-0403 Oslo, Norway.
Bjørtuft
H
H
Wiger
R
R
Holme
J
J
Seeberg
E
E
Bjørås
M
M
Brunborg
G
G
D000818:Animals; D001773:Blood Cells / Q000378:metabolism; D015153:Blotting, Western; D019757:Carbon-Oxygen Lyases / Q000378:metabolism; D002457:Cell Extracts; D048429:Cell Size; D002478:Cells, Cultured; D020552:Comet Assay; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D045647:DNA Glycosylases; D019175:DNA Methylation; D004260:DNA Repair / Q000235:genetics*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D008297:Male; D008540:Meiosis / Q000235:genetics; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D051381:Rats; D013087:Spermatids / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D013091:Spermatogenesis / Q000235:genetics; D013094:Spermatozoa / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D014498:Uracil / Q000378:metabolism; D051981:Uracil-DNA Glycosidase
D002457:Cell Extracts; D014498:Uracil; D004247:DNA; D008741:Methyl Methanesulfonate; D043223:Deoxyribonuclease IV (Phage T4-Induced); D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; D019757:Carbon-Oxygen Lyases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase