CHARACTERIZATION OF A PROTEIN RECOGNIZING MINOR-GROOVE BINDERS-DAMAGED DNA

By using electromobility shift assay (EMSA), we have identified a prot ein able to recognize the DNA only if it was previously reacted with m inor groove binders. This protein binds with very high affinity AT con taining DNA treated with minor groove binders such as distamycin A, Ho echst 33258 and 33342, CC-1065 and ethidium bromide minor groove inter calator, but not with major groove binders such as quinacrine mustard, cisplatin or melphalan, or with topoisomerase I inhibitor camptotheci n or topoisomerase II inhibitor doxorubicin. This protein was found to be present in different extracts of human, murine and hamster cells, with the human protein which appears to have a molecular weight slight ly lower than that of the other species. This protein was found to be expressed both in cancer and normal tissues. By using molecular ultraf iltration techniques as well as southwestern analysis it was estimated that the apparent molecular weight is close to 100 kDa. We can exclud e an identity between this protein and other proteins, with a similar molecular weight previously reported to be involved in DNA damage reco gnition/repair, such as topoisomerase I, mismatch repair activities su ch as the prokaryotic MutS protein and its human homologue hMSH2 or pr oteins of the nucleotide excision repair system such as ERCC1, -2, -3 and -4.