Transcriptionally active and inactive mouse beta-globin gene loci are repaired at similar rates after ultraviolet irradiation

It has been demonstrated, by Northern blot and in situ hybridization, that the mouse erythroleukaemia cell line F4N-Sofia constitutively expresses the beta-globin genes. The recently developed quantitative assay for DNA repai r has been used to study the overall repair rate in the beta-globin gene do main in this cell line after ultraviolet irradiation and to compare it with the repair rate of the same chromatin domain in mouse Ehrlich ascites tumo ur cells which do not express the beta-globin genes. The results showed tha t in both cases the 5'-end of the domain was repaired preferentially and th at the repair rates in the two cell lines were very similar despite the dif ferent transcription state of the genes.