Yeast mutant 57,0-1 gene

A 34 kDa protein (p34) plays an important function in the control of the cell cycle in all eukaryotes. It was first identified as the product of the cdc 2/cdc 28 gene in yeast mutants which caused cells to be arrested at a commitment point in G1 (Murray, 1981). However, anti-p34 antibodies injected into cells do not affect DNA synthesis but block cells in mitosis (Riabowol et al., 1989) and p34 is believed to function both at the onset of S-phase and at mitosis. 

Corey, E.J., Matsuda, S.P.T. and Bartel, B. (1993) Isolation oi an Arabidopsis thaliana gene encoding cycloartenol synthase by functional expression in a yeast mutant lacking lanosterol synthase by the use of a chromatographic screen. Proc. Natl. Acad. Sci. USA, 90,11628-32. 

Vollack, K.-U., Dittrich, B., Eerrer, A., Boronat, A. and Bach, T.J. (1994) Two radish genes for 3-hydroxy-3-methylglutaryl-CoA reductase isozymes complement mevalonate auxotrophy in a yeast mutant and yield membrane-bound active enzyme. /. Plant Physiol., 143, 479-87. 

It was mentioned earlier that the expression of HIV protease within E. coli gives rise to a phenotype, hi a similar fashion, it has been observed that phosphodiesterases (PDEs) when expressed in yeast affect the cells. These enzymes function to modulate intracellular concentrations of the cyclic mononucleotides cAMP or cGMP Yeast has two endogenous genes encoding PDEs which, when deleted, lead to elevated levels of cAMP within the ceU. The consequence to the yeast of elevated cAMP is increased sensitivity to heat shock and inability to utilize acetate as sole carbon source. These yeast mutants may be complemented by the human PDE gene and the phenotype reversed (Eigure 5.5). The use of such yeast in the search for inhibitors of PDEs with utility in, for example, asthma has been proposed" and certainly works with the known type IV PDEs inhibitor, rolipram. 

Acetolactate synthase (ALS) is the target enzyme for three unrelated classes of herbicides, the sulfonylureas, the imidazolinones, and the triazolopyrimidines. We have cloned the genes which specify acetolactate synthase from a variety of wild type plants, as well as from plants which are resistant to these herbicides. The molecular basis of herbicide resistance in these plants has been deduced by comparing the nucleotide sequences of the cloned sensitive and resistant ALS genes. By further comparing these sequences to ALS sequences obtained from herbicide-resistant yeast mutants, two patterns have become clear. First, the ALS sequences that can be mutated to cause resistance are in domains that are conserved between plants, yeast and bacteria. Second, identical molecular substitutions in ALS can confer herbicide resistance in both yeast and plants. 

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