DNA binding domains and nuclear localization signal of LEDGF: contribution of two helix-turn-helix (HTH)-like domains and a stretch of 58 amino acids of the N-terminal to the trans-activation potential of LEDGF

J Mol Biol. 2006 Jan 20;355(3):379-94. doi: 10.1016/j.jmb.2005.10.054. Epub 2005 Nov 9.

Abstract

Lens epithelium derived growth factor (LEDGF), a nuclear protein, plays a role in regulating the transcription of stress-associated genes such as heat shock proteins by binding to consensus core DNA sequences nAGGn or nGAAn or their repeats, and in doing so helps to provide cyto-protection. However, additional information is required to identify the specific structural features of LEDGF involved in gene transcription. Here we have investigated the functional domains activating and repressing DNA-binding modules, by using a DNA binding assay and trans-activation experiments performed by analyzing proteins prepared from deletion constructs. The results disclosed the DNA-binding domain of N-terminal LEDGF mapped between amino acid residues 5 and 62, a 58 amino acid residue stretch PWWP domain which binds to stress response elements (STRE; A/TGGGGA/T). C-terminal LEDGF contains activation domains, an extensive loop-region (aa 418-530) with two helix-turn-helix (HTH)-like domains, and binds to a heat shock element (HSE; nGAAn). A trans-activation assay using Hsp27 promoter revealed that both HTH domains contribute in a cooperative manner to the trans-activation potential of LEDGF. Interestingly, removal of N-terminal LEDGF (aa 1-187) significantly enhances the gene activation potential of C-terminal LEDGF (aa 199-530); thus the N-terminal domain (aa 5-62), exhibits auto-transcriptional repression activity. It appears that this domain is involved in stabilizing the LEDGF-DNA binding complex. Collectively, our results demonstrate that LEDGF contains three DNA-binding domains, which regulate gene expression depending on cellular microenvironment and thus modify the physiology of cells to maintain cellular homeostasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cloning, Molecular
  • Consensus Sequence
  • DNA / metabolism*
  • Heat-Shock Proteins / genetics
  • Helix-Turn-Helix Motifs*
  • Humans
  • Intercellular Signaling Peptides and Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Mutagenesis, Site-Directed
  • Mutation
  • Nuclear Localization Signals / genetics
  • Nuclear Localization Signals / metabolism*
  • Oxidative Stress
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Structure, Tertiary
  • Transcriptional Activation*

Substances

  • Heat-Shock Proteins
  • Intercellular Signaling Peptides and Proteins
  • Nuclear Localization Signals
  • lens epithelium-derived growth factor
  • DNA