Coordinated regulation of genes of different amino acid utilization pathways in yeasts

PALAVECINO MARCOS; CORREA GARCIA SUSANA; BERMUDEZ MORETTI MARIANA

Mar del Plata

Congreso; LI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2015

SAIB

Yeast cells can use a variety of compounds as nitrogen source through different specific pathways. Synthesis of proteins involved in each of these pathways is tightly regulated. The availability of readily transported and metabolized nitrogen sources, which are known as good nitrogen sources, results in the strong repression of genes involved in transport and metabolism of poor ones. The utilization of poor sources such as leucine, gamma-aminobutyric acid (GABA) and allantoin requires the synthesis of pathway-specific catabolic enzymes and permeases. In this work we showed that the expression of the proteins responsible for the uptake and catabolism of different poor nitrogen sources occurs sequentially following a certain order determined by a tight regulation. This order could promote the utilization of a given nitrogen source whereas the utilization of others, which may be less useful, could be down-regulated in some growth media. We demonstrated here that the transcription factor Dal81 is central in the regulation that leads to the hierarchical expression of the genes studied and, consequently, in the utilization of leucine, allantoin and GABA. The mechanisms that lead to the temporal order in the expression of genes involved in the use of poor nitrogen sources also involve another transcription factors such as Leu3 and Stp1.