ABSTRACT
The interaction between DNA and the nonhistone proteins HMGB1 and HMGB1-(A+B) has been studied using circular dichroism and scanning force microscopy. The recombinant protein HMGB1-(A+B) has no negatively charged C-terminal domain characteristic for HMGB1. Our earlier suggestion about the structural interaction of tandem HMGB1-domains of the recombinant protein with DNA was confirmed. It was shown that the C-terminal part modulates the interactions of HMGB1-domains with DNA. Without the C-terminal sequence, the HMGB1-(A+B) protein forms DNA-protein complexes with the ordered supramolecular structure.
Subject(s)
DNA/chemistry , HMGB1 Protein/chemistry , Animals , Cattle , Circular Dichroism , HMGB1 Protein/ultrastructure , Humans , Microscopy, Electron, Scanning , Protein Binding , Protein Structure, Tertiary , Recombinant Proteins/chemistry , Recombinant Proteins/ultrastructureABSTRACT
HMGB1 is a conserved chromosomal protein composed of two DNA-binding domains and an acidic C-terminal tail. There were evidences suggesting that the C-terminal tail contributed to the DNA binding specificity of the N-terminal DNA-binding domains. However, the mechanism underlining this observation is largely unknown. Our data first confirmed the previous study with NMR that showed a direct interaction between HMGB1's C-terminal tail and its N-terminal domains. We further demonstrated that this interaction can be competed more efficiently by a DNA with four-way junction structure than by a linear double-stranded DNA. Mutations within the N-terminal region, that disrupt its binding to the C-terminal tail, abolished HMGB1's ability to distinguish the linear DNA and the four-way junction DNA. Those data suggested a unique mechanism designed by nature that utilizes a protein's negatively charged C-terminal tail to enhance its DNA-binding domain's specificity to certain structured DNAs.
Subject(s)
DNA/chemistry , HMGB1 Protein/chemistry , Binding Sites , DNA/ultrastructure , HMGB1 Protein/ultrastructure , Protein Binding , Sensitivity and Specificity , Structure-Activity RelationshipABSTRACT
Abnormal accumulation of alpha-synuclein filaments in Lewy bodies is a neuropathological hallmark of Parkinson's disease and sequestration of cellular protein into these protein aggregates may contribute to the degenerative process. We identified the transcriptional co-factor high mobility group protein 1 (HMGB-1) as a ligand for alpha-synuclein filaments by a filament spin-down technique, mass spectrometric peptide mapping and immunoblotting. HMGB-1 binds preferentially to aggregated alpha-synuclein and is present in alpha-synuclein filament-containing Lewy bodies isolated from brain tissue affected with dementia with Lewy bodies or Parkinson's disease. Our results demonstrate that alpha-synuclein filaments hold the potential for disturbing the cellular gene expression as they can sequester a component involved in cellular transcription regulation.
