URA3 is a gene on the Vth chromosome of the yeast Saccharomyces cerevisiae . Its systematic name is YEL021W . URA3 is often used in molecular biological studies of yeast as a marker gene (a gene used to mark regions of chromosomes or plasmids ). It encodes orotodin-5'-phosphate decarboxylase, an enzyme that catalyzes one of the synthesis reactions of pyrimidine ribonucleotides ( RNA monomers) [1] .
Usage
The loss of orotodine-5'-phosphate decarboxylase activity leads to cell growth arrest. Such cells grow only on the medium into which uracil or uridine is added. If, as a result of transformation, the URA3 gene appears in yeast, then the enzyme activity is restored, as a result of which the cells can again grow on the medium without uracil or uridine. This mechanism allows positive selection of cells carrying this gene. If 5-FOC (5-fluororic acid) is added to the culture of such yeast, then the active orotodin-5'-phosphate decarboxylase converts 5-fluororic acid into the toxic compound 5-fluorouracil , which leads to cell death. This allows selection against yeast cells carrying this gene.
Since the URA3 gene allows both positive and negative selection, it is widely used as a genetic marker of DNA transformation in many genetic and molecular biological techniques for bacteria and many species of fungi. This is one of the most important genetic markers of yeast . Although the URA3 gene allows efficient and convenient selection, it still has a significant drawback. The main disadvantage is that cells that have accumulated enough mutations in the URA3 gene can grow on a medium with 5-FOC. Before using the newly created strain, it should be checked by a second method, such as PCR , to make sure that it really has the desired properties.
External links
S. cerevisiae database (2005) URA3 gene. https://web.archive.org/web/20080604040222/http://db.yeastgenome.org/cgi-bin/locus.pl?locus=ura3#summaryParagraph (accessed 16/10/07).
Notes
- ↑ Flynn, PJ; Reece, RJ Activation of transcription by metabolic intermediates of the pyrimidine biosynthetic pathway (Eng.) // Molecular and cellular biology : journal. - 1999. - Vol. 19 , no. 1 . - P. 882-888 . - PMID 9858611 .