UVB and γ‐Radiation Induce the Expression of mRNAs Encoding the Ribosomal Subunit L13A in Rat Keratinocytes

Ultraviolet B radiation produces an array of cellular perturbations in the skin. We isolated a keratinocyte cDNA encoding the rat 60S ribosomal subunit protein L13a following differential cDNA library screening with UVB-en-riched probes. In contrast to the reported structure of liver L13a, the keratinocyte L13a cDNA contains a longer 3′-untranslated region. Northern blot analysis detected two L13a mRNA transcripts, ?800 bp and ?1.2 kb, in keratinocytes and a variety of rat tissues. Both L13a mRNA transcripts were induced by UVB irradiation, for-skolin and -γ-irradiation. In contrast, no induction of L13a mRNA transcript levels was observed following exposure of keratinocytes to 12-O-tetradecanoylphorbol-13-acetate, serum and the DNA damage-inducing agents methyl methanesulfonate or 4-nitroquinoUne-N-oxide. These observations suggest that increased expression of ribosomal subunit genes may be a molecular component of the keratinocyte response to UVB in particular and not part of a nonspecific response to DNA damage.