Transcripcional regulation of GDH1 in Saccharomyces cerevisiae

RIEGO, L.; AVENDAÑO, A.; GONZALEZ, A.

Universidad Simón Bolivar. Caracas, Venezuela.

Congreso; III Congreso Latinoamericano de Micología; 1999

Asociación Latinoamericana de Micología

Three pathways for ammonium assimilation and glutamate biosynthesis have been described in S. cerevisiae. Two are mediated by the NADP+s-dependent glutamate dehydrogenases (encoded by GDH1 and GDH3). An alternative pathway comprises a cycle between glutamine synthetase and glutamate synthase (GOGAT). In order to study the expression of GDH1 under different growth conditions. The promoter region of the gene was fused in frame with the LacZ gene. The LacZ fusions were used to transform a wild type strain and several mutants altered in transcriptional factors such as Gln3p, Gat1p or Gcn4p. A collection of 5' deletions of the promoter region were also constructed, fused in frame to the LacZ gene and used to transform the wild type strain. Our results show that GDH1 expression is positively regulated by Gln3p in all the growth conditions tested. GDHI expression is not nitrogen source dependent; in contrast to the enzimatic product which it is negatively modulated by nitrogen source. When cells were grown in ethanol as a sole carbon source GDH1 expression is 3-fold higher than cells grown on glucose.