In vivo acetylation of HMG1 protein enhances its binding affinity to distorted DNA structures

The postsynthetic acetylation of HMG1 protein has been known for more than 20 years, but the effect of this modification on the properties of the prot ein has not been studied so far. Acetylated HMG1 was isolated from cells gr own in the presence of sodium n-butyrate and identified as a monoacetylated protein, modified at lysine 2. Acetylated and parental forms of HMG1 were compared relative to their binding affinity to distorted DNA structures. By using mobility shift assay to determine the dissociation constants, we sho w that acetylation enhanced the ability of HMG I to recognize UV light- or cisplatin-damaged DNA and four-way junctions. Since the modified lysine lie s adjacent to the HMG1 DNA-binding domain, the results obtained were attrib uted to acetylation-induced conformational change in HMG1. The potential ro le of acetylation in modulating the interactions of HMG1 with both damaged DNA and other proteins is discussed.