Two dominant-acting selectable markers for gene transfer studies in XXXX cells.

@entity1 @entity104 @entity1522 @entity2491 @entity2125 @entity535 @entity3793 @entity19 @entity32183 @entity14614 @entity2340 @entity46398 @entity62466 @entity526
We report the development of two dominant-acting genetic markers useful for monitoring gene transfer in @entity1 cells that are based on prokaryotic genes encoding key steps in the synthesis of the essential @entity1522 , @entity2340 and @entity3793 . Under appropriate conditions, expression of these genes obviates the nutritional requirements for their respective @entity535 products. Expression of the trpB gene of @entity526 , which encodes the beta subunit of @entity2340 synthase (EC 4.2.1.20), allows @entity1 cell survival and multiplication in medium containing @entity104 in place of @entity2340 . The hisD gene of @entity2491 encodes @entity32183 dehydrogenase (EC 1.1.1.23), which catalyzes the two-step @entity2125 +-dependent oxidation of @entity46398 to @entity14614 . In medium lacking @entity3793 and containing @entity32183 , only @entity1 cells expressing the hisD product survive. The selection is a double one in that the provided precursor @entity32183 is itself toxic to animal cells through its inhibition of histidyl-tRNA synthetase; thus, the dehydrogenase both removes an inhibitor and forms a required end product. Alternatively, the his selection may be carried out under conditions in which the dehydrogenase serves mainly to detoxify @entity32183 . For either the trp or his selections the substitute nutrient ( @entity104 or @entity32183 ) is readily available, inexpensive, stable, permeable to cells, and convertible to the end product in a step controlled by a single gene. Vectors based upon @entity19 retrovirus and papovavirus backbones have been successfully employed for both genes, allowing selection in a range of cell types, including 3T3, @entity62466 , and HeLa. These dominant selective schemes should provide generally useful and inexpensive alternatives to others currently in use, such as the gpt, neo, hygro, dhfr, and tk selections.
