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Molecular and Cellular Biology, May 1999, p. 3360-3371, Vol. 19, No. 5
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Transcriptional Induction by Aromatic Amino Acids in Saccharomyces cerevisiae

Ismaïl Iraqui, Stéphan Vissers, Bruno André, and Antonio Urrestarazu*

Laboratoire de Physiologie Cellulaire et de Génétique des Levures, Université Libre de Bruxelles---Campus Plaine CP244, B-1050 Brussels, Belgium

Received 20 July 1998/Returned for modification 30 September 1998/Accepted 15 February 1999

Aromatic aminotransferase II, product of the ARO9 gene, catalyzes the first step of tryptophan, phenylalanine, and tyrosine catabolism in Saccharomyces cerevisiae. ARO9 expression is under the dual control of specific induction and nitrogen source regulation. We have here identified UASaro, a 36-bp upstream element necessary and sufficient to promote transcriptional induction of reporter gene expression in response to tryptophan, phenylalanine, or tyrosine. We then isolated mutants in which UASaro-mediated ARO9 transcription is partially or totally impaired. Mutations abolishing ARO9 induction affect a gene called ARO80 (YDR421w), coding for a Zn2Cys6 family transcription factor. A sequence highly similar to UASaro was found upstream from the YDR380w gene encoding a homolog of bacterial indolepyruvate decarboxylase. In yeast, this enzyme is postulated to catalyze the second step of tryptophan catabolism to tryptophol. We show that ARO9 and YDR380w (named ARO10) have similar patterns of transcriptional regulation and are both under the positive control of Aro80p. Nitrogen regulation of ARO9 expression seems not directly to involve the general factor Ure2p, Gln3p, Nil1p, Uga43p, or Gzf3p. ARO9 expression appears, rather, to be mainly regulated by inducer exclusion. Finally, we show that Gap1p, the general amino acid permease, and Wap1p (Ycl025p), a newly discovered inducible amino acid permease with broad specificity, are the main aromatic amino acid transporters for catabolic purposes.

* Corresponding author. Mailing address: Laboratoire de Physiologie Cellulaire et de Génétique des Levures, Université de Bruxelles---Campus Plaine CP244, Bd du Triomphe, B-1050 Brussels, Belgium. Phone: 32-2-650-5428. Fax: 32-2-650-5421. E-mail: laurrest{at}ulb.ac.be.

Molecular and Cellular Biology, May 1999, p. 3360-3371, Vol. 19, No. 5
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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