Effects of Ultraviolet Irradiation on the Level of mRNA of Ornithine Decarboxylase in the Hairless Mouse Skin

Abstract

Ornithine decarboxylase (ODC) is a rate-limiting enzyme of polyamine biosynthesis and a well-established marker of the tumor promotion process. Ultraviolet-B (UV-B) irradiation induced this activity remarkably in hairless mouse skin. To elucidate this mechanism molecular biologically, mRNA was extracted from the mouse skin and the ODC mRNA level was evaluated by Northern blotting analysis using a ³²P-labelled ODC cDNA probe. UV-B irradiation (90 mJ/cm²) markedly increased the ODC mRNA level (2.0-and 2.6-fold of control at 4 and 24 hours, respectively). On the other hand, the expression of the actin gene, an important house-keeping gene, did not increase by irradiation. These results showed that increased ODC mRNA levels by UV-B was responsible for the UV-B-induced ODC activity.