当前位置： SCI文献检索 > DNA REPAIR期刊下所有文献 > Base excision repair and nucleotide excision repair contribute to the removal of N-methylpurines from active genes.

Base excision repair and nucleotide excision repair contribute to the removal of N-methylpurines from active genes.

Abstract：

:Many different cellular pathways have evolved to protect the genome from the deleterious effects of DNA damage that result from exposure to chemical and physical agents. Among these is a process called transcription-coupled repair (TCR) that catalyzes the removal of DNA lesions from the transcribed strand of expressed genes, often resulting in a preferential bias of damage clearance from this strand relative to its non-transcribed counterpart. Lesions subject to this type of repair include cyclobutane pyrimidine dimers that are normally repaired by nucleotide excision repair (NER) and thymine glycols (TGs) that are removed primarily by base excision repair (BER). While the mechanism underlying TCR is not completely clear, it is known that its facilitation requires proteins used by other repair pathways like NER. It is also believed that the signal for TCR is the stalled RNA polymerase that results when DNA damage prevents its translocation during transcription elongation. While there is a clear role for some NER proteins in TCR, the involvement of BER proteins is less clear. To explore this further, we studied the removal of 7-methylguanine (7MeG) and 3-methyladenine (3MeA) from the dihydrofolate reductase (dhfr) gene of murine cell lines that vary in their repair phenotypes. 7MeG and 3MeA constitute the two principal N-methylpurines formed in DNA following exposure to methylating agents. In mammalian cells, alkyladenine DNA alkyladenine glycosylase (Aag) is the major enzyme required for the repair of these lesions via BER, and their removal from the total genome is quite rapid. There is no observable TCR of these lesions in specific genes in DNA repair proficient cells; however, it is possible that the rapid repair of these adducts by BER masks any TCR. The repair of 3MeA and 7MeG was examined in cells lacking Aag, NER, or both Aag and NER to determine if rapid overall repair masks TCR. The results show that both 3MeA and 7MeG are removed without strand bias from the dhfr gene of BER deficient (Aag deficient) and NER deficient murine cell lines. Furthermore, repair of 3MeA in this region is highly dependent on Aag, but repair of 7MeG is equally efficient in the repair proficient, BER deficient, and NER deficient cell lines. Strikingly, in the absence of both BER and NER, neither 7MeG nor 3MeA is repaired. These results demonstrate that NER, but not TCR, contributes to the repair of 7MeG, and to a lesser extent 3MeA.

journal_name

DNA Repair (Amst)

journal_title

DNA repair

authors

Plosky B,Samson L,Engelward BP,Gold B,Schlaen B,Millas T,Magnotti M,Schor J,Scicchitano DA

doi

10.1016/s1568-7864(02)00075-7

keywords:

subject

Has Abstract

pub_date

2002-08-06 00:00:00

pages

683-96

issue

eissn

1568-7864

issn

1568-7856

pii

S1568786402000757

journal_volume

pub_type

杂志文章

在线工具

Base excision repair and nucleotide excision repair contribute to the removal of N-methylpurines from active genes.