The role of the GATA factors Gln3p, Nil1p, Dal80p and the Ure2p on ASP3 regulation in Saccharomyces cerevisiae.

The role of Gln3p, Nil1p, Dal80p and Ure2p in the nitrogen regulation of ASP3, which codes for the periplasmic Saccharomyces cerevisiae asparaginase II, was investigated. Analysis of enzyme levels and mRNA(ASP3) in two wild-type strains and gln3, nil1, gln3nil1, gln3ure2, nil1ure2, nil1dal80, ure2, dal80 and ure2dal80 mutant cells allowed the study of the qualitative and quantitative regulatory role of the GATA factors and Ure2p on ASP3 expression. The simultaneous presence of Gln3p and Nil1p is a required condition for full gene transcription. Enzyme activity doubled upon nitrogen starvation of either ammonium-grown (possibly due to Nil2p/Deh1p derepression) or proline-grown (due to Dal80p derepression) cells. The ure2 mutation increased enzyme levels five-fold in fresh ammonium-grown cells and ten-fold in fresh proline-grown cells. The combined effects of the ure2 mutation and nitrogen starvation on ammonium- or proline-grown cells resulted in an overall 10-20-fold enzyme activity increase, respectively, in comparison with the wild-type cells.