DNA Repair and Ultraviolet Mutagenesis in Cells From a New Patient With Xeroderma Pigmentosum Group G and Cockayne Syndrome Resemble Xeroderma Pigmentosum Cells

Abstract

Xeroderma pigmentosum (XP)/Cockayne syndrome (CS) complex is a combination of clinical features of two rare genetic disorders in one individual. A sun-sensitive boy (XP20BE) who had severe symptoms of CS, with dwarfism, microcephaly, retinal degeneration, and mental impairment, had XP-type pigmentation and died at 6 y with marked cachexia (weight 14.5 lb) without skin cancers. We evaluated his cultured cells for characteristic CS or XP DNA-repair abnormalities. The level of ultraviolet (UV)-induced unscheduled DNA synthesis was less than 5% of normal, characteristic of the excision-repair defect of XP. Cell fusion studies indicated that his cells were in XP complementation group G. His cells were hypersensitive to killing by UV, and their post-UV recovery of RNA synthesis was abnormally low, features of both CS and XP. Post-UV survival of plasmid pSP189 in his cells was markedly reduced, and post-UV plasmid mutation frequency was higher than with normal cells, as in both CS and XP. Sequence analysis of the mutated plasmid marker gene showed normal frequency of plasmids with multiple base substitutions, as in CS, and an abnormally increased frequency of G:C-->A:T mutations, a feature of XP. Transfection of UV-treated pRSVcat with or without photoreactivation revealed that his cells, like XP cells, could not repair either cyclobutane pyrimidine dimers or non-dimer photoproducts. These results indicate that the DNA-repair features of the XP20BE (XP-G/CS) cells are phenotypically more like XP cells than CS cells, whereas clinically the CS phenotype is more prominent than XP.

A semi-automated non-radioactive system for measuring recovery of RNA synthesis and unscheduled DNA synthesis using ethynyluracil derivatives

“…Normal 1BR [16] and 48BR [16], XP-patient-derived XP12BR (XP-D) [13], XP15BR (XP-A) [17], XP13BR (XP-C) [13], XP21BR (XP-C, this study) and XP20BE (XP-G) [18], and CS-patient-derived CS16PV (CS-A, Miria Stefanini, personal communication), CS20PV (CS-B, Miria Stefanini, personal communication) and CS10LO (CS-B) [19] cells were human primary fibroblasts. Normal 277 and 701 (both purchased from RIKEN), and XP-patientderived XPL5 (XP-V) [20] and XPL15OS (XP-A) [20] are EBV-immortalised Blymphoblastoids (LCLs).…”

Definition of a Short Region of XPG Necessary for TFIIH Interaction and Stable Recruitment to Sites of UV Damage

“…Fibroblasts and lymphoblastoid cells were cultured as described previously (8,24). The primary fibroblasts used were XPCS1BD (patient), XP20BE (from a severely affected XP-G/CS individual ( [33]), GM01630 (XP-A), XP11BE (XP-B), GM00671 (XP-C), XP1BR (XP-D), XP3BR (XP-G), and 250BR (wild type). Simian virus 40-transformed fibroblasts were from XP-G/CS patient XPCS1RO (10), who was previously known as 94RD27 (16,38).…”

“…Most CS patients have no XP connection and instead carry mutations in the CSA and CSB genes, but XP/CS symptoms are also found in XP-B and some XP-D individuals (26). The onset of CS in XP-G/CS patients is particularly early and severe, with reported life expectancies ranging from only months to less than 7 years (12,16,22,33,53,57).…”

Elevated Urinary Levels of 8-Hydroxy-2′-deoxyguanosine in a Japanese Child of Xeroderma Pigmentosum/Cockayne Syndrome Complex with Infantile Onset of Nephrotic Syndrome

“…DNA repair tests, such as the measurement of post-UV unscheduled DNA synthesis and post-UV cell survival, were performed using the methods previously described (Moriwaki et al 1996). These methods can help identify the gene responsible for the disease manifestation in the patient among the 6 genes, XPA, XPB, XPC, XPD, XPF, and XPG, which are known to cause 8 DNA repair diseases.…”