High impact information on HMGN1

• Nucleosome cores have two specific binding sites for nonhistone chromosomal proteins HMG 14 and HMG 17 [1].
• DNA intercalators induce specific release of HMG 14, HMG 17 and other DNA-binding proteins from chicken erythrocyte chromatin [2].
• Chloroquine (CQ) intercalation also results in the selective liberation of HMG 14 and HMG 17, but, in addition, selectively releases other nuclear proteins (including histone H1A) in a pH- and ionic strength-dependent fashion [2].
• The intercalating agents ethidium bromide (EtBr) and propidium iodide induce the specific release of high mobility group proteins HMG 14 and HMG 17 under low ionic strength conditions [2].
• No significant changes in cell phenotype were observed in cells harboring either singly or doubly disrupted HMG-17 genes, and no compensatory changes in HMG-14 or histone protein levels were observed [3].

Biological context of HMGN1

• The deduced amino acid sequence is unique and different from all other known HMG-14 and -17 sequences [4].
• Phosphorylation also reduced the ability of HMG 14 to protect the ends of nucleosomal DNA from thermal denaturation [5].
• These data indicate that each of two molecules of HMG 14 and/or HMG 17 is bound to the double-stranded core DNA at two discrete sites: to the 3' and 5' ends of the DNA and at a distance of 20 to 25 base-pairs from each DNA terminus inside the nucleosome on a histone-free DNA region [6].
• An additional factor, histone acetylation, was preferentially associated with the HMG 14/17 bound chromatin fraction of avian erythrocytes, but it was not associated with the HMG 14/17 bound chromatin fraction of metabolically active HTC cells [7].

Anatomical context of HMGN1

• The characterisation of 1SF monomer nucleosomes from hen oviduct and the partial characterisation of a third HMG14/17-like in such nucleosomes [8].
• In the thyroid, HMG 14 displays TSH-dependent phosphorylation that is mediated by cAMP-dependent protein kinase (A-kinase) [5].
• Comparison with the corresponding data for the calf thymus proteins shows that 11% of the residues in HMG14 protein and 5% of the residues in HMG17 protein differ between the two species [9].
• Hybridization analysis of membranes obtained by this method revealed that the HMG 14/17 bound nucleosomes of avian erythrocytes and rat hepatic tumor (HTC) cells were enriched, about 2-fold, in actively transcribed genes and also inactive but DNase I sensitive genes [7].

Associations of HMGN1 with chemical compounds

• The resulting pattern of single-stranded DNA fragments suggests that the NH2 termini of the core histones no longer bind strongly to the nucleosomal DNA of the "early" mononucleosomes, and thus enhance the rate of DNase I digestion, while the presence of HMG 14 increased the solubility of these mononucleosomes [10].
• Thermal denaturation and circular dichroism show a dramatic reversal of the effects of urea on nucleosomes when HMG 14 or 17 is bound, indicating stabilization of the nucleosome by HMG proteins [11].
• Cyclic adenosine 3',5'-monophosphate-dependent phosphorylation of HMG 14 inhibits its interactions with nucleosomes [5].
• A new method was developed to allow direct membrane transfer of DNA from HMG 14/17 bound and unbound nucleosomes, which have been separated by acrylamide gel electrophoresis [7].
• Phosphorylation of HMG 14 proteins from calf thymus and avian erythrocytes was studied using a cyclic GMP-dependent protein kinase from bovine lung [12].

Physical interactions of HMGN1

• It is concluded that one molecule of HMG 1 or 2 binds to the 40 base pairs of linker DNA whereas the HMG 14 or 17 molecules associate with the nucleosomal core [13].

Other interactions of HMGN1

• Conditions have been established which have led to the isolation of mononucleosomes which contain the high mobility group (HMG) proteins, in particular HMG 14, from mature chicken erythrocyte nuclei after extended micrococcal nuclease digestion [10].
• HMG-14 and HMG-17 form a family of ubiquitous non-histone chromosomal proteins and have been reported to bind preferentially to regions of active chromatin structure [14].
• The slower moving band contains the three HMG proteins HMG14, 17 and Y but lacks histone H1 [8].
• When nucleosome preparations from chicken erythrocyte nuclei stripped of HMG proteins are partially titrated with HMG14/17, the nucleosome-HMG complex fraction is enriched in beta-globin gene sequences [15].
• Two molecules of HMG 14 or 17 are accommodated by particles with 140 or 180 base pairs of DNA whereas HMG 1 or 2 are only bound by the larger specimens irrespective of the presence of HMG 14/17 [13].

Analytical, diagnostic and therapeutic context of HMGN1

• The binding of HMG 14 or 17 to nucleosomes results in greater stability of the nucleosomal DNA as shown by circular dichroism and thermal denaturation [11].
• Electron microscopy reveals no major structural alterations in the nucleosome upon binding of HMG 14 or 17 [11].

References