Role of the Dal80 transcription factor in the control of all leucine permeases in S. cerevisiae

PALAVECINO MARCOS; CORREA GARCIA SUSANA; BERMUDEZ MORETTI MARIANA

Rosario

Congreso; L Reunion anual de la Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular; 2014

SAIB

Yeast can use a wide variety of nitrogen compounds. However, the ability to synthesize enzymes and permeases for catabolism of poor nitrogen sources is limited in the presence of a rich one. This general mechanism of transcriptional control is called nitrogen catabolite repression. There are different permeases that can transport all naturally occurring amino acids. In this work we studied the regulation of Agp1 and Gap1, two amino acid permeases with broad substrate range, and Bap2 and Bap3, both involved in uptake of leucine, isoleucine and valine. Expression of these genes under different growth conditions was analysed. We also studied the expression of transcription factors that regulate these genes, and the interaction of these factors with the regulatory region of the permease genes. We found that in the absence of amino acids only Gap1 is expressed although the negative factor Dal80 is acting on its promoter. After addition of leucine, the transcription factors Dal81 and Stp1 bind to AGP1 promoter, Stp1 binds to BAP2 promoter, and consequently expression of AGP1 and BAP2 rises. In the presence of a rich nitrogen source and leucine, Bap3 seems to be the only permease capable of incorporating amino acids into yeast cells. The expression of these permeases is regulated so that an amino acid is incorporated only by one or another permease, depending on the growth conditions.