Decrease in class pi glutathione transferase mRNA levels by ultraviolet irradiation of cultured rat keratinocytes.
The effect of ultraviolet (UV) B irradiation on pi class glutathione transferase (GST-P) gene expression was examined in cultured rat keratinocytes. Immunoblotting demonstrated GST-P to be the major GST form in the cells, and it was significantly decreased following irradiation. Northern blot analysis revealed that the mRNA decreased to 10-25% of the initial value 24 h after irradiation at a dose of 40 mJ/cm2. No remarkable changes were observed at earlier time points. Hydrogen peroxide treatment enhanced GST-P mRNA expression, with a 70% increase at 250 microM concentration. Alterations in possible trans-acting factors were examined to clarify the mechanism of repression by UV irradiation. c-Jun mRNA was induced 3.5-fold at 4 h after irradiation, but by 24 h fell to a lower level than that observed initially. c-Fos mRNA was increased 10-fold at 1 h but was completely suppressed at 12 and 24 h. Thus, the changes of c-Jun and c-Fos mRNA differed from that of GST-P mRNA. The level of mRNA for silencer factor-B was decreased to less than 10% at 12 h. UV irradiation of cells transfected with the chloramphenicol acetyltransferase (CAT) reporter gene containing enhancer (GPE I) or silencer regions of the GST-P gene did not suppress CAT activity. Although basal expression of the GST-P gene was mainly dependent on GPE I, altered expression of c-jun, c-fos and other genes coding for factors possibly trans-acting on GPE I did not appear to be responsible for the decreased GST-P mRNA levels.
Nakano
H
H
Second Department of Biochemistry, Hirosaki University School of Medicine.
Kimura
J
J
Kumano
T
T
Hanada
K
K
Satoh
K
K
Hashimoto
I
I
Tsuchida
S
S
D000818:Animals; D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D016762:Genes, fos / Q000528:radiation effects; D016758:Genes, jun / Q000528:radiation effects; D005982:Glutathione Transferase / Q000096:biosynthesis* / Q000145:classification / Q000235:genetics; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D015603:Keratinocytes / Q000201:enzymology* / Q000378:metabolism / Q000528:radiation effects*; D012333:RNA, Messenger / Q000378:metabolism* / Q000528:radiation effects; D051381:Rats; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic / Q000528:radiation effects; D014466:Ultraviolet Rays
D007527:Isoenzymes; D012333:RNA, Messenger; D015534:Trans-Activators; D006861:Hydrogen Peroxide; D005982:Glutathione Transferase