Transcription coupled repair of 8-oxoguanine in murine cells: The Ogg1 protein is required for repair in nontranscribed sequences but not in transcribed sequences

Transcription coupled repair of 8-oxoguanine in murine cells: The Ogg1 protein is required for repair in nontranscribed sequences but not in transcribed sequences

^*Laboratoire de Radiobiologie de l'ADN, UMR217, Commissariat à l'Energie Atomique–Centre National de la Recherche Scientifique, BP6, 92265-Fontenay aux Roses, France; ^†Department of Molecular Biology, Institute of Medical Microbiology, University of Oslo, The National Hospital, N-0027 Oslo, Norway; ^‡Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, United Kingdom; and ^§Laboratory of Genetic Instability and Cancer, UPR2160 Centre National de la Recherche Scientifique, 94801-Villejuif, France

Edited by Richard B. Setlow, Brookhaven National Laboratory, Upton, NY, and approved May 19, 2000 (received for review March 28, 2000)

Abstract

To assess the role of the Ogg1 DNA glycosylase in the transcription-coupled repair (TCR) of the mutagenic lesion, 7,8-dihydro-8oxoguanine (8-OxoG), we have investigated the removal of this lesion in wild-type and ogg1 ^−/− null mouse embryo fibroblast (MEF) cell lines. We used nonreplicating plasmids containing a single 8-OxoG·C base pair in a different assay that allowed us to study the removal of 8-OxoG located in a transcribed sequence (TS) or in a nontranscribed sequence (NTS). The results show that the removal of 8-OxoG in a wild-type MEF cell line is faster in the TS than in the NTS, indicating TCR of 8-OxoG in murine cells. In the homozygous ogg1 ^−/− MEF cell line, 8-OxoG was not removed from the NTS whereas there was still efficient 8-OxoG repair in the TS. Expression of the mouse Ogg1 protein in the homozygous ogg1 ^−/− cell line restored the ability to remove 8-OxoG in the NTS. Therefore, we have demonstrated that Ogg1 is essential for the repair of 8-OxoG in the NTS but is not required in the TS. These results indicate the existence of an Ogg1-independent pathway for the TCR of 8-OxoG in vivo.

Footnotes

↵ ¶ To whom reprint requests should be addressed. E-mail:boiteux{at}dsvidf.cea.fr.
This paper was submitted directly (Track II) to the PNAS office.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.140137297.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.140137297
Abbreviations:

8-OxoG,

7,8-dihydro-8-oxoguanine;

TCR,

transcription-coupled repair;

MEF,

mouse embryo fibroblast;

TS,

transcribed sequence;

NTS,

nontranscribed sequence;

AP,

apurinic/apyrimidinic;

SV,

simian virus;

CC,

covalently closed