Mutations play critical roles in cancer initiation and genetic disorders, as well as in microbial pathogenesis and resistance to drugs. Because mutations also generate genetic variability that is required for evolution, cells have mechanisms not only for avoiding excess mutation during normal growth conditions, but also for promoting mutations in response to environmental and physiological stress. In this proposal we will investigate of a recently discovered pathway for mutagenesis that was found to be triggered, surprisingly, by a mutation (mutA) in a gene coding for a tRNA. Our investigation in the previous funding period has led to several important discoveries: mistranslation induced by genetic defects in protein synthesis, or exposure to the antibiotic streptomycin, can induce this mutagenic pathway, named TSM for translational stress-induced mutagenesis. TSM is distinct from the well known SOS mutagenesis pathway, and appears to require homologous recombination functions under certain conditions. TSM appears to be mediated by error-prone DMA synthesis by a modified form of DMA polymerase III. These findings imply the existence of previously undescribed links between translation and DMA replication, and raise the possibility that mutator phenotypes with significance for cell survival, adaptation, cancer initiation, and aging can arise through defects in a much larger repertoire of target genes than previously recognized. The induction of this pathway by antibiotic exposure, and potentially by amino acid starvation suggest that environmental and physiological stress can also increase mutagenesis by this pathway. Our work further shows that aminoglycoside antibiotics pose a mutagenic risk through this previously unrecognized mechanism. Here, we propose to investigate the mechanisms by which mistranslation leads this mutator phenotype through the following three Specific Aims. (1) Test the hypothesis that direct mistranslation of a replicative DMA polymerase leads to the TSM phenotype. (2) Test the hypothesis that in Rec- mutA cells there is selective killing of cells undergoing episodic aberrant replication cycles. (3) Test the hypothesis that the TSM phenotype results from episodic hyper-mutagenesis cycles.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM058253-06
Application #
6949103
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Program Officer
Portnoy, Matthew
Project Start
1998-08-01
Project End
2008-08-31
Budget Start
2005-09-01
Budget End
2006-08-31
Support Year
6
Fiscal Year
2005
Total Cost
$262,668
Indirect Cost
Name
University of Medicine & Dentistry of NJ
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
623946217
City
Newark
State
NJ
Country
United States
Zip Code
07107
Humayun, M Zafri; Ayyappan, Vasudevan (2013) Potential roles for DNA replication and repair functions in cell killing by streptomycin. Mutat Res 749:87-91
Gautam, Satyendra; Kalidindi, Raju; Humayun, M Zafri (2012) SOS induction and mutagenesis by dnaQ missense alleles in wild type cells. Mutat Res 735:46-50
Al Mamun, Abu Amar M; Humayun, M Zafri (2009) Spontaneous mutagenesis is elevated in protease-defective cells. Mol Microbiol 71:629-39
Al Mamun, Abu Amar M (2007) Elevated expression of DNA polymerase II increases spontaneous mutagenesis in Escherichia coli. Mutat Res 625:29-39
Al, Mamun Abu Amar M; Gautam, Satyendra; Humayun, M Zafri (2006) Hypermutagenesis in mutA cells is mediated by mistranslational corruption of polymerase, and is accompanied by replication fork collapse. Mol Microbiol 62:1752-63
Wang, Ge; Alamuri, Praveen; Humayun, M Zafri et al. (2005) The Helicobacter pylori MutS protein confers protection from oxidative DNA damage. Mol Microbiol 58:166-76
Balashov, Sergey; Humayun, M Zafri (2004) Specificity of spontaneous mutations induced in mutA mutator cells. Mutat Res 548:9-18
Balashov, Sergey; Humayun, M Zafri (2003) Escherichia coli cells bearing a ribosomal ambiguity mutation in rpsD have a mutator phenotype that correlates with increased mistranslation. J Bacteriol 185:5015-8
Balashov, Sergey; Humayun, M Zafri (2002) Mistranslation induced by streptomycin provokes a RecABC/RuvABC-dependent mutator phenotype in Escherichia coli cells. J Mol Biol 315:513-27
Al Mamun, Abu Amar M; Marians, Kenneth J; Humayun, M Zafri (2002) DNA polymerase III from Escherichia coli cells expressing mutA mistranslator tRNA is error-prone. J Biol Chem 277:46319-27

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