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A Non-random Mouse Model for Pharmacological Reactivation of Mecp2 on the Inactive X Chromosome
Published on: May 22, 2019
Codominance associated with overexpression of certain XPD mutations
S Kadkhodayan1, F Coin, E P Salazar
1Biology and Biotechnology Research Program, L441, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551-0808, USA.
Mutation Research
|February 22, 2001
Summary
Mutations in the XPD gene cause DNA repair disorders like xeroderma pigmentosum (XP). This study shows some XPD mutations lead to non-functional repair, causing disease despite appearing to repair DNA.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Mutations in the XPD gene are linked to xeroderma pigmentosum (XP), Cockayne syndrome (XP-CS), and trichothiodystrophy (TTD).
- XP involves nucleotide excision repair (NER) deficiency, increasing skin cancer risk.
- TTD presents with developmental issues, brittle hair, and scaly skin, sometimes with NER defects.
Purpose of the Study:
- To investigate how specific XPD gene mutations affect the dominant/recessive behavior of XPD protein.
- To understand the functional consequences of identified XPD mutations in Chinese hamster ovary (CHO) cells.
Main Methods:
- Studied T46I and R75W XPD mutations in UV-sensitive CHO cell lines.
- Assessed XPD helicase activity and NER function using cell-extract excision assays.
- Examined the effects of overexpressing various mutant XPD alleles in wild-type CHO cells.
Main Results:
- T46I and R75W mutants showed significantly reduced XPD helicase activity and complete NER defect.
- Paradoxically high unscheduled DNA synthesis in these mutants was attributed to abortive repair.
- Overexpression of XP-specific (R683W) and helicase-domain (K48R) mutations induced codominant negative phenotypes.
Conclusions:
- Certain XPD mutations result in non-productive DNA repair, explaining observed phenotypes in XP and related disorders.
- Codominant negative effects of overexpressed mutant XPD alleles suggest distinct mechanisms for XP and TTD.
- Overexpression of mutant XPD alleles can be a tool to induce NER deficiency in cell lines for research.
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