Hoar D I, Waghorne C
Am J Hum Genet. 1978 Nov;30(6):590-601.
Cockayne syndrome (CS) is a rare recessive genetic disease characterized in part by premature ageing and photosensitive skin. Because of the latter characteristic, this syndrome was considered to be an example of a UV-sensitive DNA repair-defective human disorder. We demonstrated normal levels of UV-induced unscheduled DNA synthesis (UDS) in four unrelated CS patients that show hypersensitivity to both UV and Mitomycin C (MMC). At low UV exposure, CS DNA shows a dose-dependent decrease in size. By contrast, heterozygotes appear to have a threshold below which there is little change in size of single strand DNA. Immediately following UV or MMC treatment, CS DNA is deficient in high molecular weight species, but undergoes a normal transition to larger DNA during a chase interval in the presence or absence of caffeine. This suggests a defect in replication or excision repair and no defect in post-replication repair (PRR). Pulse studies performed in the presence of hydroxyurea (HU) also reveal a deficient production of large DNA, suggesting the defect is in repair. As these cells have normal UDS and normal PRR, the basis for their UV sensitivity must be distinct from that observed in xeroderma pigmentosum (XP).
科凯恩综合征（CS）是一种罕见的隐性遗传病，部分特征为早衰和光敏性皮肤。由于后一特征，该综合征被认为是对紫外线敏感的DNA修复缺陷型人类疾病的一个例子。我们在四名对紫外线和丝裂霉素C（MMC）均过敏的无关CS患者中证明了紫外线诱导的非预定DNA合成（UDS）水平正常。在低紫外线照射下，CS DNA的大小呈剂量依赖性下降。相比之下，杂合子似乎有一个阈值，低于该阈值单链DNA的大小几乎没有变化。在紫外线或MMC处理后立即观察，CS DNA缺乏高分子量物种，但在有无咖啡因的追踪间隔期间会正常转变为更大的DNA。这表明复制或切除修复存在缺陷，而复制后修复（PRR）没有缺陷。在羟基脲（HU）存在下进行的脉冲研究也显示大DNA的产生不足，表明缺陷在于修复。由于这些细胞具有正常的UDS和正常的PRR，它们对紫外线敏感的基础一定与着色性干皮病（XP）中观察到的不同。
