Intracellular distribution of HMG1, HMG2 and UBF change following treatment with cisplatin.

Cisplatin (CDDP) is a widely used cancer chemotherapeutic agent. CDDP forms well characterized intrastrand cross-links between adjacent purines in genomic DNA. In mammalian cells, these lesions are repaired by the nucleotide excision repair system. An early event in the recognition and processing of cis-Pt-DNA adducts may well involve the binding of specific proteins to the sites of damage. Several proteins have been identified, including high mobility group (HMG) proteins 1 and 2 and upstream binding factor (UBF), which recognize CDDP-DNA. However, the physiological significance of this binding has not been established. In this study, we have utilized antibodies to these proteins to examine the effect of CDDP on their intracellular distribution. Marked changes in the immunofluorescent staining pattern of HMG1/HMG2 were noted in cells treated with CDDP. At higher drug concentrations, the distribution of UBF also changed, from a clustered appearance associated with the nucleoli to more diffuse nuclear staining. These results demonstrate that HMG1/HMG2 and UBF respond to drug treatment, presumably by recognizing cis-Pt-DNA adduct formation in intact cells. Hence, these proteins may play an important role in directing the response of tumor cells following exposure to CDDP.