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DNA polymerase θ promotes CAG•CTG repeat expansions in Huntington's disease via insertion sequences of its catalytic domain
- Source :
- The Journal of Biological Chemistry
- Publication Year :
- 2021
-
Abstract
- Huntington's disease (HD), a neurodegenerative disease characterized by progressive dementia, psychiatric problems, and chorea, is known to be caused by CAG repeat expansions in the HD gene HTT. However, the mechanism of this pathology is not fully understood. The translesion DNA polymerase θ (Polθ) carries a large insertion sequence in its catalytic domain, which has been shown to allow DNA loop-outs in the primer strand. As a result of high levels of oxidative DNA damage in neural cells and Polθ's subsequent involvement in base excision repair of oxidative DNA damage, we hypothesized that Polθ contributes to CAG repeat expansion while repairing oxidative damage within HTT. Here, we performed Polθ-catalyzed in vitro DNA synthesis using various CAG•CTG repeat DNA substrates that are similar to base excision repair intermediates. We show that Polθ efficiently extends (CAG)n•(CTG)n hairpin primers, resulting in hairpin retention and repeat expansion. Polθ also triggers repeat expansions to pass the threshold for HD when the DNA template contains 35 repeats upward. Strikingly, Polθ depleted of the catalytic insertion fails to induce repeat expansions regardless of primers and templates used, indicating that the insertion sequence is responsible for Polθ's error-causing activity. In addition, the level of chromatin-bound Polθ in HD cells is significantly higher than in non-HD cells and exactly correlates with the degree of CAG repeat expansion, implying Polθ's involvement in triplet repeat instability. Therefore, we have identified Polθ as a potent factor that promotes CAG•CTG repeat expansions in HD and other neurodegenerative disorders.
- Subjects :
- Polθ, DNA polymerase θ
congenital, hereditary, and neonatal diseases and abnormalities
DNA Repair
DNA polymerase
DNA hairpin
Polβ, polymerase β
DNA-Directed DNA Polymerase
Biochemistry
AP, abasic
chemistry.chemical_compound
HEK, human embryonic kidney
ROS, reactive oxygen species
FBS, fetal bovine serum
Catalytic Domain
mental disorders
Humans
RFC, replication factor C
Insertion sequence
8-oxoG, 8-oxo-guanine
Molecular Biology
BER, base excision repair
OGG1, 8-oxo-guanine DNA glycosylase 1
biology
DNA synthesis
Chemistry
PCNA, proliferating cellular nuclear antigen
triplet repeats
Cell Biology
Base excision repair
WCLs, whole-cell lysates
Molecular biology
DNA polymerase θ
TdT, terminal deoxynucleotidyl transferase
Proliferating cell nuclear antigen
nervous system diseases
HD, Huntington’s disease
TNRs, trinucleotide repeats
Huntington Disease
biology.protein
PolθΔi2, insertion 2–depleted Polθ
Primer (molecular biology)
Trinucleotide repeat expansion
Trinucleotide Repeat Expansion
DNA
DNA Damage
HeLa Cells
Research Article
Huntington’s disease
Subjects
Details
- ISSN :
- 1083351X
- Volume :
- 297
- Issue :
- 4
- Database :
- OpenAIRE
- Journal :
- The Journal of biological chemistry
- Accession number :
- edsair.doi.dedup.....ebae6f95d3f821dae8a620705cf59bbb