Previous support from the NSF has allowed the following objectives to be largely accomplished. Development of mutant tRNA genes that would suppress termination at amber codons 2) Isolation of mammalian cell lines or cell conditions that allow efficient suppression of termination at nonsense codons 3) solation of mutants of animal viruses with nonsense lesions in essential genes, and 4) the use of these reagents to explore the genetics and molecular biology of both animal viruses and mammalian cells. Further and continuing objectives are to 1) develop a series of cell lines with opal and ocher suppressor tRNA's 2) develop an inducible suppressor system that does not involve gene amplification 3) the isolation of nonsense mutants of adenovirus and 4) to continue to develop methods for homologous recombination in mammalian cells. Much of the power of genetic systems such as yeast and Drosophila is a result of the sophisticated technology available to investigators working with those systems. The general theme of this research is to develop such methods for use with mammalian cells. %%% The value of genetic systems often correlates with the methodology available to those working with those systems. The use of suppressor tRNA's in prokaryotic and yeast systems allowed data to be accumulated which could not have been otherwise obtained. The ease with which genes can be inserted at the proper position in the yeast genome has made yeast one of the most useful of experimental genetic systems. The work projected in this proposal is designed to make some of those tools and methods available to investigators working with mammalian cells and mammalian viruses. New suppressor tRNA's will be constructed, new nonsense mutants of adenovirus will be sought and methods for homologous recombination in mammalian cells will be devised.
