Poster #RP228
REPRESSOR ROLE OF GZF3 ON THE EXPRESSION OF ASP3 IN SACCHAROMYCES CEREVISIAE
Richard Almeida*, Elvira Carvajal*
*Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
Periplasmic asparaginase II is coded by ASP3 in yeast. The enzyme hydrolyses asparagine to aspartic acid and ammonia. There are four copies of ASP3 in chromosome XII, located near the rRNA coding loci. The production of asparaginase II and the level of mRNAASP3 follow the pattern of genes regulated by nitrogen. Their expression is decreased when cells are grown on media containing rich nitrogen sources such as ammonium sulfate and glutamine, and is increased when the nitrogen source is considered poor such as proline and urea. This regulation is carried by a network of proteins known as Ure2 and four members of the GATA family. Two of them, Gln3 and Gat1 are activators and Dal80 and Gzf3 are repressors. This work shows the role of Gzf3 on the mRNAASP3 level under different conditions. A set of isogenic strains was constructed and cells were grown in media containing 0.2% of ammonium sulfate, or 0.1% of proline, or 0.1% of urea as nitrogen source. The ASP3 expression was analyzed by northern blotting in total RNA extracts from fresh cells or nitrogen starved. The data indicated that Gzf3 homodimer has lower repressor activity on ASP3 as compared to Dal80.