Identification of the XPG region that causes the onset of Cockayne syndrome by using Xpg mutant mice generated by the cDNA-mediated knock-in method.

Abstract

In addition to xeroderma pigmentosum (XP), mutations in the human XPG gene cause early onset of Cockayne syndrome (CS) in some patients (XPG/CS). The CS-causing mutations in such patients all produce truncated XPG proteins. To test the hypothesis that the CS phenotype, with characteristics such as growth retardation and a short life span in XPG/CS patients, results from C-terminal truncations, we constructed mutants with C-terminal truncations in mouse XPG (Xpg) (from residue D811 to the stop codon [XpgD811stop] and deletion of exon 15 [Xpg Delta ex15]). In the XpgD811stop and Xpg Delta ex15 mutations, the last 360 and 183 amino acids of the protein were deleted, respectively. To generate Xpg mutant mice, we devised the shortcut knock-in method by replacing genomic DNA with a mutated cDNA fragment (cDNA-mediated knock in). The control mice, in which one-half of Xpg genomic DNA fragment was replaced with a normal Xpg cDNA fragment, had a normal growth rate, a normal life span, normal sensitivity to UV light, and normal DNA repair ability, indicating that the Xpg gene partially replaced with the normal cDNA fragment retained normal functions. The XpgD811stop homozygous mice exhibited growth retardation and a short life span, but the Xpg Delta ex15 homozygous mice did not, indicating that deletion of the last 360 amino acids results in the CS phenotype but deletion of the last 183 amino acids does not. The XpgD811stop homozygous mice, however, exhibited a slightly milder CS phenotype than did the Xpg null mutant mice, indicating that the XpgD811stop protein still retains some Xpg function that affects the severity of the CS phenotype.

• Authors: Naoko Shiomi, Seiji Kito, Masaki Oyama, Tsukasa Matsunaga, Yoshi-Nobu Harada, Masahito Ikawa, Masaru Okabe, Tadahiro Shiomi
• Journal: Molecular and cellular biology (Mol Cell Biol) Vol. 24 Issue 9 Pg. 3712-9 (May 2004) ISSN: 0270-7306 [Print] United States
• PMID: 15082767 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA excision repair protein ERCC-5
• DNA, Complementary
• DNA-Binding Proteins
• Nuclear Proteins
• Transcription Factors
• Endonucleases

Topics

• Animals
• Cells, Cultured
• Child
• Cockayne Syndrome (genetics, physiopathology)
• DNA Damage
• DNA, Complementary (genetics, metabolism)
• DNA-Binding Proteins (genetics, metabolism)
• Endonucleases
• Exons
• Fibroblasts (cytology, metabolism, radiation effects)
• Gene Targeting
• Humans
• Infant
• Mice
• Mice, Inbred C57BL
• Mice, Transgenic
• Mutation
• Nuclear Proteins
• Survival Rate
• Transcription Factors
• Ultraviolet Rays