High mobility group box 1 protein (HMGB1) stimulates the nuclear accumulation of p53

Abstract p53 is usually regarded as a tumour suppressor protein but its constant activation may result in pro-tumorigenic inflammation. The activation of p53 can be provoked by an increase in its concentration as a result of high level transcription, by transformation of the p53 protein to an active conformation or by its translocation from the cytoplasm to the nucleus. p53 can be activated by a wide variety of stress signals that a cell might encounter during malignant progression, such as genotoxic damage, oncogene activation and hypoxia. We found that the HMGB1 protein can play the role of a signal molecule that provokes the accumulation of p53 in the nucleus. Only the full-length protein stimulated the translocation of p53 from the cytosol to the nucleus and the effect was considerably strong and almost equal to that generated by the positive control actinomycin D. The truncated tail less form of HMGB1 was not functional. This supported the hypothesis that the C terminus plays an important role in regulating the properties of HMGB1