RESUMO

Irradiation of DNA with UV light induces pyrimidine dimers and (6-4) photoproducts. The presence of one of these photolesions in the restriction site of a given endonuclease inhibits DNA cleavage and induces the formation of fragments by incomplete DNA digestion which appear as additional, facultative bands in Southern hybridization autoradiograms. The number and size of these fragments show a positive correlation with the UV dose. The response to UV light of immunoglobulin light-chain constant kappa and heavy-chain constant mu genes was analyzed with 2 specific probes. Constant kappa and mu genes when irradiated as part of the chromatin of living lymphocytes showed a UV sensitivity similar to that of naked DNA. The same genes from granulocytes had 50-60 times lower UV sensitivity. When cells were allowed to repair photolesions for 24 h the facultative bands from granulocytes disappeared indicating that these cells were able to remove photolesions from constant kappa and mu genes. Facultative bands from lymphocytes showed a smaller decrease of density after 24 h repair. This suggests that lymphocytes are less efficient than granulocytes in removing UV damage from constant kappa and mu genes.

Assuntos

Reparo do DNA , Genes de Imunoglobulinas/efeitos da radiação , Raios Ultravioleta , Autorradiografia , Southern Blotting , DNA/metabolismo , DNA/efeitos da radiação , Dano ao DNA , Enzimas de Restrição do DNA/metabolismo , Densitometria , Eletroforese em Gel de Ágar , Genes de Imunoglobulinas/genética , Granulócitos/efeitos da radiação , Humanos , Regiões Constantes de Imunoglobulina/genética , Regiões Constantes de Imunoglobulina/efeitos da radiação , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias Pesadas de Imunoglobulinas/efeitos da radiação , Cadeias Leves de Imunoglobulina/genética , Cadeias Leves de Imunoglobulina/efeitos da radiação , Linfócitos/efeitos da radiação , Soluções