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SOS factors involved in translesion synthesis
R L Napolitano1, I B Lambert, R P Fuchs
1Unité Propre de Recherche 9003 du Centre National de la Recherche Scientifique, Cancérogenèse et Mutagenèse Moléculaire et Structurale, Ecole Supérieure de Biotechnologie de Strasbourg, Blvd S. Brant, 67400 Strasbourg, France.
Summary
DNA damage can cause mutations during replication. In E. coli, the SOS response and umuDC gene products are crucial for translesion synthesis past lesions, especially within repetitive DNA sequences.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Mutations are permanent DNA alterations arising from replication errors on damaged templates.
- Translesion synthesis (TLS) bypasses DNA lesions, requiring SOS-inducible gene products in E. coli, including the umuDC operon.
Purpose of the Study:
- To investigate the in vivo mechanisms of TLS past a 2-acetylaminofluorene (AAF) adduct within frameshift mutation hotspots.
- To elucidate the roles of SOS functions, specifically umuDC, in TLS through repetitive DNA sequences.
Main Methods:
- Construction of single-stranded DNA vectors with site-specific AAF adducts in repetitive sequences.
- Analysis of DNA replication survival and mutation fixation under SOS-induced and non-induced conditions in E. coli.
- Assessment of umuDC+ dependence for elongation from different replication intermediates.
Main Results:
- AAF adducts within repetitive sequences significantly hindered DNA replication, with only 2-5% survival without SOS induction.
- SOS induction increased survival by 10-fold, indicating enhanced TLS.
- Elongation from non-slipped intermediates required functional umuDC+; elongation from slipped intermediates was umuDC+-independent but required another SOS function.
Conclusions:
- Replication stalling at AAF adducts in repetitive sequences leads to misaligned primer/template intermediates, causing frameshift errors.
- Distinct SOS functions, including umuDC and an uncharacterized factor, mediate TLS through different replication intermediates during mutagenic bypass.