HMGB1 Interacts with Many Apparently Unrelated Proteins by Recognizing Short Amino Acid Sequences

Abstract

The chromatin high mobility group protein 1 (HMGB1) is a very abundant and conserved protein that is structured into two HMG box domains plus a highly acidic C-terminal domain. From the ability to bind DNA nonspecifically and to interact with various proteins, several functions in DNA-related processes have been assigned to HMGB1. Nevertheless, its functional role remains the subject of controversy. Using a phage display approach we have shown that HMGB1 can recognize several peptide motifs. A computer search of the protein data bases found peptide homologies with proteins already known to interact with HMGB1, like p53, and have allowed us to identify new potential candidates. Among them, transcriptional activators like the heterogeneous nuclear ribonucleoprotein K (hnRNP K), repressors like methyl-CpG binding protein 2 (MeCP2), and co-repressors like the retinoblastoma susceptibility protein (pRb) and Groucho-related gene proteins 1 (Grg1) and 5 (Grg5) can be found. A detailed analysis of the interaction of Grg1 with HMGB1 confirmed that the binding region contained the sequence homologous to one of the peptides identified. Our results have led us to propose that HMGB1 may play a central role in the stabilization and/or assembly of several multifunctional complexes through protein-protein interactions.In the eukaryotic cell nucleus of all vertebrate cell types, HMGB1 1 (formerly named HMG1, see Ref. 1 for a revised nomenclature) is one of the most abundant non-histone proteins. HMGB1 has been shown to be essential because knockout mice die 24 h after birth (2). HMGB1 is highly conserved, particularly in mammals and to a lesser extent throughout the animal kingdom. HMGB1 is structured into three domains, two basic HMG boxes (HMG domains A and B) and a highly acidic C-terminal domain, which confer an overall dipolar appearance to this protein (see Refs. 3-5 for reviews). Each of the HMG boxes is formed by two short and one long ␣-helix that upon folding produce an L-or V-shaped three-dimensional domain structure (6 -8). Whereas the acidic C-terminal domain is presumably involved in the modulation of HMGB1 activity, the HMG box domains allow the protein to bind to linear DNA with moderate affinity and to highly structured (3-and 4-way junction DNA, cruciform DNA) or distorted DNA (bent or kink DNA, bulged DNA, cisplatin-modified DNA) with higher affinity, but always without sequence specificity. The concave surface of the L-or V-shaped HMG box domain contacts the DNA in the minor groove in two slightly different ways introducing important modifications in the structure of DNA, in particular a strong bend (reviewed in Ref. 5). Presumably, these features will be of relevance for the biological functions in which HMGB1 has been involved (DNA repair, recombination, replication, and transcription).The activity of HMGB1 is not solely mediated by its ability to bind to DNA. Indeed, HMGB1 and the related HMGB2 protein can interact through their HMG box domains with a broad range of proteins ranging from nuclear cell prote...

HMGB1 Develops Enhanced Proinflammatory Activity by Binding to Cytokines

“…These results show that HMGB1 itself has only minimal proinflammatory properties, but it acquires much greater activity through its role as a carrier protein for cytokines or other mediators capable of inducing cell activation. HMGB1 has previously been shown to bind in the intracellular milieu to a wide range of proteins, including transcriptional factors, steroid receptors, and viral proteins (34). The present findings, as well as those of other laboratories (16,17), demonstrate that extracellular proteins, such as cytokines and DNA-containing immune complexes, can also bind to HMGB1, creating a proinflammatory complex.…”

“…The present findings, as well as those of other laboratories (16,17), demonstrate that extracellular proteins, such as cytokines and DNA-containing immune complexes, can also bind to HMGB1, creating a proinflammatory complex. Although the sites for interaction between HMGB1 and IL-1␤ were not examined in these experiments, previous studies have shown that the A and B boxes, and possibly the highly acidic C terminal domain, are involved in HMGB1 binding to proteins (34).…”

High mobility group box 1 protein interacts with multiple Toll-like receptors

“…Because distinct sets of ligands have been shown to interact with TLR2 and TLR4, it is likely that different regions of HMGB1 may be responsible for the associations observed in the present experiments with each of these receptors. HMGB1 has been shown to interact with a wide range of proteins, including transcriptional factors (21,47), steroid receptors (3,28), and viral components (7), through its A and B box domains, and possibly through the highly acidic COOH-terminal domain (10). With a phage display approach, HMGB1 was shown to recognize more than 12 different peptide sequences, indicating that HMGB1 is capable of associating with multiple proteins (10).…”

“…HMGB1 has been shown to interact with a wide range of proteins, including transcriptional factors (21,47), steroid receptors (3,28), and viral components (7), through its A and B box domains, and possibly through the highly acidic COOH-terminal domain (10). With a phage display approach, HMGB1 was shown to recognize more than 12 different peptide sequences, indicating that HMGB1 is capable of associating with multiple proteins (10). In those studies, different peptide sequences were found to associate with either the A or B box of HMGB1, suggesting that HMGB1 does not have a restricted interaction sequence.…”

The Role of HMGB1 in the Pathogenesis of Inflammatory and Autoimmune Diseases

“…As noted, HMGB1 has a unique regional structure in which different sequences allow interaction with biochemically disparate molecules (33). This property suggests that extracellular HMGB1 could be less discreet in its interaction with receptors in comparison to a conventional cytokine.…”