| Summary: | 碩士 === 國立中興大學 === 生物醫學研究所 === 94 === The p53 binding protein 1 (53BP1) is a highly conserved DNA damage checkpoint protein in all eukaryotes. 53BP1 contains two BRCT domains, which are present in several proteins involved in DNA repair and DNA damage-signaling pathways. Upon DNA damage, 53BP1 rapidly relocalized to DNA double-strand breaks and forms discrete nuclear foci. It has been shown that 53BP1 is required for DNA damage checkpoint protein activation and tumor suppression. 53BP1 facilitates the end-joining repair and class-switch repair processes. Impaired function of DNA damage response gives rise to chromosomal instability that can result in tumorigenesis. Although the mechanism of 53BP1 has been proposed to prevent genomic instability and tumorigenesis, the detail is still unclear.
Our results showed that 53BP1 mRNA expression is nearly the same in 6 lung cancer cell lines. By western blot analysis, 53BP1 was expressed in 7 lung cancer cell lines. About 60-70% lung cancer tissue specimens expressed 53BP1 mRNA and protein. Interestingly, a high molecular weight protein－53BP1'' was highly expressed in H226 and MCF-7 cell lines. Furthermore, expression of 53BP1'' was markedly increased than 53BP1 after cisplatin treatment. Hence, our results suggest that the different forms of 53BP1 contain distinct biological significance and may play diverse role in tumorigenesis.
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