a.a, amino acid; BER, base excision repair; CPD, cyclobutane pyrimidine dimer; DMSO, dimethyl sulfoxide; e.m., electron microscopy; ENU, ethyl nitrosourea; FISH, fluorescence in situ hybridisation; HGPS, Hutchinson-Gilford progeria syndrome; HRP, horseradish peroxidase; MEF, mouse embryonic fibroblasts; NER, nucleotide excision repair; PGal, phenyl-β-d-galactosidase; pfu, plaque-forming units; RD, restrictive dermopathy; ROS, reactive oxygen species; TC-NER, transcription-coupled NER; wt, wild type. The gene discussed is ZMPSTE24; the disease is Hutchinson-Gilford progeria syndrome.