CDCA7 and HELLS mutations undermine nonhomologous end joining in centromeric instability syndrome

Area of Science:

• Genetics
• Molecular Biology
• Cell Biology

Background:

• Mutations in CDCA7 and HELLS cause ICF syndromes 3 and 4.
• These genes encode a zinc finger protein and a chromatin remodeler, respectively.

Purpose of the Study:

• To investigate the molecular mechanisms underlying ICF syndromes.
• To explore the role of CDCA7 and HELLS in DNA repair pathways.

Main Methods:

• Coimmunoprecipitation assays to identify protein interactions.
• Functional assays measuring classical nonhomologous end joining (C-NHEJ) activity.
• Analysis of DNA damage response markers and chromosomal abnormalities in deficient cells.

Main Results:

• CDCA7 interacts with C-NHEJ proteins Ku80 and Ku70, and HELLS.
• CDCA7 and HELLS deficiency impairs C-NHEJ activity and DNA damage repair.
• Deficient cells exhibit increased apoptosis, aneuploidy, and centrosome amplification.
• Similar defects observed in cells with mutations in other ICF genes (DNMT3B, ZBTB24) and patient-derived cells.

Conclusions:

• CDCA7 and HELLS are essential for C-NHEJ pathway integrity.
• Impaired C-NHEJ contributes to genomic instability and cellular defects in ICF syndromes.
• CDCA7 and HELLS play a role in maintaining CG methylation at centromeric regions.