HMGB proteins

Agresti A, Bianchi ME (2003) HMGB proteins and gene expression. Curr Opin Genet Dev 13 170-178... 

Fig. 1. HMG boxes in the abundant chromosomal HMGB proteins and in other DNA-binding proteins.

The interaction of the abundant HMGB proteins with both nucleosomal particles lacking linker histones and with linker histones themselves in vitro is well documented. A soluble chromatin fraction released from mouse myeloma nuclei contained mononucleosomes associated with almost stoichiometric amounts of HMGB1,2 but lacking histone HI [81]. Nhp6ap binds directly to nucleosomal particles reconstituted with chicken histones (i.e., a single histone octamer... 

HMGB proteins including HMGBl ([96,97] A. Simpson and J. O. Thomas, unpublished) and HMG-D [87] can also interact directly in vitro with histone HI. The interaction of HMG-D is independent of the acidic tail (suggesting that, in this case at least, non-specific charge interactions involving the tail can be excluded) but requires aminoacids 75-100, which comprise a short linker and basic region between the HMG box and the tail [87]. 

In addition to a potential role of HMGB proteins in nucleosome assembly, it has recently become apparent that many chromatin remodeling complexes either contain, or can associate with, a polypeptide containing an HMG-box homologous to the HMGBl B domain (Table 2). Examples of such complexes include the BAF (a mammalian SWI/SNF related complex [106]) and the Drosophila BRM (brahma)... 

The postulated interaction of the acidic tail of abundant HMGB proteins with core histones might suggest possible functional differences between the two major... 

Fig. 4. Possible mechanism for HMGB proteins in facilitating the unwrapping of nucleosomal DNA. The model postulates that the binding of an HMGB protein at an exit/entry point for the wrapped DNA increases the accessibility of the wrapped DNA both at the exit/entry points adjacent to the bound HMGB protein and also at internal positions. Such a conformational change would facilitate the binding both of sequence-specific regulatory proteins and of remodeling complexes. Adapted from Ref. [119] with permission.

Wong, B., Masse, J.E., Yen, Y.-M., Feigon, J., and Johnson, R.C. (2002) Binding to cisplatin-modified DNA by the Saccharomyces cerevisiae HMGB protein NHP6A. Biochemistry 41, 5404-5414. 

Travers, A.A. (2003) Priming the nucleosome—a role for HMGB proteins EMBO Rep. 4, 131-136. Bonaldi, T., Langst, G., Strohner, R., Becker, P.B., and Bianchi, M.E. (2002) The DNA chaperone HMGBl facilitates ACF/CHRAC-dependent nucleosome sliding. EMBO J. 21, 6865-6873. 

Krohn, N.M., Yanagisawa, S., and Crasser, K.D. (2002) Specificity of the stimulatory interaction between chromosomal HMGB proteins and the transcription factor Dof2 and its negative regulation by protein kinase CK2-mediated phosphorylation. J. Biol. Chem. 277, 32438-32444. 

Since HMGB proteins appear to impair intrinsic nucleosome mobility while at the same time enhancing enzymatically driven translocation [202] this observation is not wholly consistent with a simple unwrapping from one end of the... 

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