Disease relevance of tyrT

• When introduced by transformation, a functioning supF gene in progeny plasmid recovered from COS7 cells allows suppression of a lacZ amber mutation in the indicator Escherichia coli host [1].
• Base changes were also localized at G:C pairs in the mutation of the supF gene, induced by riboflavin photosensitization, which specifically yields 7,8-dihydro-8-oxoguanine (8-oxoG) [2].
• From mouse cells exposed to 254-nm ultraviolet light (12J/m2), 78,510 phage were rescued, of which 8 were found to have mutant supF genes [3].
• In order to study mutagenesis in mammalian cells, stable mouse L-cell lines were established with multiple copies of a lambda phage vector that contains the supF gene of Escherichia coli as a target for mutagenesis [3].
• The bacterial supF gene and the origins of DNA replication from polyomavirus and the ColE1 replicon also have been included in this vector [4].

High impact information on tyrT

• In our assay, amber mutations in a bacteriophage lambda genome that serves as the target for integration are suppressed by integration of an MLV derivative that carries the E. coli supF gene [5].
• In all three, the relaxed phenotype was suppressed by supD, supE, supF or sup6 [6].
• A single-site mutant of Escherichia coli glutaminyl-synthetase (D235N, GlnRS7) that incorrectly acylates in vivo the amber suppressor supF tyrosine transfer RNA (tRNA(Tyr] with glutamine has been described [7].
• In addition, L15 contains an extra tyrosine residue when suppressed by supF [8].
• We show that an aminoacylated amber suppressor tRNA (supF) derived from the E. coli tyrosine tRNA can be imported into COS1 cells and acts as a suppressor of amber codons, whereas the same suppressor tRNA imported without prior aminoacylation does not, suggesting that the supF tRNA is not a substrate for any mammalian aminoacyl-tRNA synthetase [9].

Chemical compound and disease context of tyrT

• The Escherichia coli lacZ ochre mutant strain U118 was converted to an amber mutant and suppressed with supF, which inserts tyrosine [10].
• A DNA repair-deficient mutant, KS46 (uvrA-), of Escherichia coli was transformed with the plasmid DNA, and the transformants carrying mutations on the supF gene were selected as nalidixic acid-resistant colonies [11].
• Treatment of the UV-irradiated plasmid DNA with Escherichia coli photolyase to reverse pyrimidine cyclobutane dimers (the predominant UV-induced photoproduct) before replication prevented the UV-induced inhibition of replication and reduced the frequency of mutations in supF to background levels [12].
• Mutagenesis by the suspected major mutagenic metabolite of activated benzo[a]pyrene, which is (+)-anti-BPDE, was analyzed with a new system, which permits the selection of supF- mutations in an Escherichia coli plasmid using lactose minimal plates [13].
• Peroxynitrite (ONOO-) induces oxidative and nitrosative DNA damage, and previous studies by our group have shown that it is strongly mutagenic in the supF shuttle vector pSP189 replicated in Escherichia coli MBL50 cells [14].

Biological context of tyrT

• Untreated plasmids and plasmids containing 6.6 BPDE residues were transfected into COS7 cells, and the progeny were assayed for mutations in the supF gene [1].
• The target for detecting mutations was the 200-base pair gene for a tyrosine suppressor tRNA (supF), inserted at the EcoRI site in shuttle vector p3AC (Sarkar et al., Mol. Cell. Biol. 4:2227-2230, 1984) [1].
• (+)anti-DB[a,j]A-DE induced primarily point mutations in supF in SOS-induced cells [15].
• The spontaneous mutation frequency in the supF gene is approximately 0.7 and approximately 1.0 x 10(-6) without and with SOS induction, respectively [16].
• Furthermore, supF suppression of lacIam26 results in a lactose repressor that has an uninducible, lacIS genotype, which makes the cells unable to grow on lactose minimal plates [16].

Anatomical context of tyrT

• When a shuttle vector containing a tyrosine suppressor tRNA (supF) gene as a target for mutagenesis replicated in a monkey kidney cell line, the frequency of SupF+ mutations was 2.3 +/- 0.5 x 10(-3) [17].
• The resulting virus (MMTVsupF) induced mammary tumors at the expected rate in infected mice, deleted the appropriate T-cell population by virtue of its superantigen gene, and stably retained the supF gene after passage via the milk to female offspring [18].
• To explore the mutagenic potential of equine estrogen metabolites, a double-stranded pMY189 shuttle vector carrying a bacteria suppressor tRNA gene, supF, was exposed to 4-OHEQ and transfected into human fibroblast [19].
• The supF tRNA of the plasmid pSP189 was used as the mutational target in a cell-free and Chinese hamster ovary (CHO) cell system to study hydroquinone mutagenicity [20].
• Rat-liver microsomes were used to activate aflatoxin B1 for in vitro modification of the pS189 shuttle vector and the related signature vector pSP189, both of which carry the Escherichia coli supF gene as a mutational target [21].

Associations of tyrT with chemical compounds

• In contrast, spontaneous or mutagen-induced supF- mutations in pUB3 prevent suppression of lacIam26 and result in constitutive expression of the lactose operon, which permits growth on lactose minimal plates [16].
• The overall distribution of methylglyoxal-induced mutations detected in the supF gene was different from that for the spontaneous mutations [22].
• It is shown here that a 'minimal' GlnRS, i.e. a GlnRS from which domains interacting with the acceptor-end and the anticodon of the tRNA have been deleted, has enzymatic activity and can charge a tRNA(Tyr)-derived amber suppressor (supF) with glutamine [23].
• Polyacrylamide gel and agarose gel electrophoresis analysis of 137 plasmids with mutations in the supF gene indicated that 70% (21/30) from untreated plasmids contained deletions or insertions or showed altered gel mobility, whereas only 28% (30/107) of those derived from BPDE-treated plasmids contained such alterations [24].
• The insertion/substitution vector is a 2638-base pair plasmid containing the pBR322 origin of replication and ampicillin resistance determinant, a T4 gene 23 promoter/synthetic supF tRNA gene fusion, and a polylinker with eight unique restriction enzyme recognition sites [25].

Analytical, diagnostic and therapeutic context of tyrT

• The plasmid pUB3, which contains the mutation target gene, supF, was modified with (+)anti-DB[a,j]A-DE in vitro (two to five adducts/plasmid) and then transformed into bacteria by electroporation [15].
• Sequence analysis of the supF genes of these mutants showed that all (37/37) the base substitutions occurred at C:G base pairs; 68% (23/37) of the base substitutions were base transversions, while 32% (12/37) were transitions [26].
• A lambda phage-based shuttle vector system, utilizing the supF transfer RNA gene of Escherichia coli, questioned the mutagenicity of AHA in established cell cultures derived from somatic tissue while the standard sex-linked recessive lethal assay measured mutational events in vivo [27].

References