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The HMG1 ta(i)le

Alexander M Polyanichko1, Elena V Chikhirzhina, Alexei N Skvortsov

  • 1Molecular Biophysics Department, Physical Faculty of St.-Petersburg State University, 1 Ulianovskaya st., Stary Petergof, St.-Petersburg, 198904, Russia.

Journal of Biomolecular Structure & Dynamics
|May 25, 2002
PubMed

Insights

The C-terminal tail of High Mobility Group 1 (HMG1) protein significantly alters DNA structure. Removing this tail causes DNA to form highly ordered structures when bound by HMG1-domains.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Structural Biology

Background:

  • High Mobility Group 1 (HMG1) protein is involved in DNA binding and structural modulation.
  • Understanding HMG1's interaction with DNA is crucial for elucidating its regulatory and architectural roles.
  • The influence of HMG1's distinct domains on DNA complex formation requires further investigation.

Purpose of the Study:

  • To investigate structural changes in DNA/protein complexes using circular dichroism (CD) spectroscopy.
  • To compare the DNA-binding behavior of HMG1 and a truncated variant (HMG1-(A+B)) lacking the C-terminal acidic tail.
  • To determine the role of the C-terminal tail in modulating HMG1-DNA interactions and complex structures.

Main Methods:

  • Circular dichroism (CD) spectroscopy was employed to analyze structural changes in DNA/protein complexes.
  • Studies were conducted using both purified calf thymus HMG1 protein and recombinant HMG1-(A+B) protein.
  • Experiments were performed at varying ionic strengths (15 mM NaCl and 150 mM NaCl) to assess differential binding.

Main Results:

  • At low ionic strength (15 mM NaCl), both HMG1 and HMG1-(A+B) exhibited similar interactions with calf thymus DNA.
  • At higher ionic strength (150 mM NaCl), HMG1-(A+B) binding to DNA resulted in distinct structural changes compared to HMG1.
  • HMG1-(A+B)/DNA complexes showed DNA fractions with very high optical activity, suggesting the formation of highly ordered DNA structures.

Conclusions:

  • The negatively charged C-terminal acidic tail of HMG1 plays a critical role in modulating its interaction with DNA.
  • The absence of the C-terminal tail leads to the formation of highly ordered DNA structures, indicating a significant conformational change.
  • These findings highlight the functional importance of the HMG1 C-terminal tail and its domains in DNA binding and structural regulation.

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