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A polyglutamine expansion disease protein sequesters PTIP to attenuate DNA repair and increase genomic instability

Hong Xiao1, Zhigang Yu, Yipin Wu

  • 1Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA.

Human Molecular Genetics
|June 28, 2012
PubMed

Insights

Mutant poly-glutamine (Q) proteins disrupt DNA repair by sequestering PTIP, a key DNA repair protein. This leads to increased DNA damage and accelerated degeneration in spinal and bulbar muscular atrophy (SBMA).

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Genetics

Background:

  • Glutamine (Q) expansion diseases are linked to CAG triplet repeat expansions in genes, leading to mutant protein-driven pathogenesis.
  • The precise mechanisms by which mutant poly-Q proteins cause cell death and disease progression remain unclear.

Purpose of the Study:

  • To investigate the interaction between mutant androgen receptor (AR) in spinal and bulbar muscular atrophy (SBMA) and the DNA repair protein PTIP.
  • To elucidate the role of PTIP sequestration in the pathogenesis of poly-Q expansion diseases.

Main Methods:

  • Examined the interaction between mutant AR and PTIP in cellular models.
  • Assessed the localization of PTIP in response to ionizing radiation in the presence and absence of poly-Q AR.
  • Evaluated DNA damage sensitivity and chromosomal instability.
  • Utilized a mouse model of SBMA with altered PTIP gene dosage.

Main Results:

  • Mutant poly-Q AR specifically interacts with PTIP, sequestering it away from radiation-induced nuclear foci.
  • PTIP sequestration leads to increased sensitivity to DNA-damaging agents and chromosomal instability.
  • SBMA mouse models exhibit DNA damage in muscle nuclei, with accelerated atrophy when PTIP is reduced.

Conclusions:

  • Mutant poly-Q AR disrupts DNA repair pathways by sequestering PTIP, contributing to cellular degeneration in poly-Q diseases.
  • This interaction provides a novel mechanism for understanding pathogenesis in diseases like SBMA.
  • Targeting PTIP interactions may offer therapeutic strategies for poly-Q expansion disorders.

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