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Cloning of the ASN1 and ASN2 genes encoding asparagine synthetases in Saccharomyces cerevisiae : differential regulation by the CCAAT‐box‐binding factor
Author(s) -
Dang VanDinh,
Valens Michèle,
BolotinFukuhara Monique,
DaignanFornier Bertrand
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1996.d01-1715.x
Subject(s) - biology , gene , asparagine , auxotrophy , asparagine synthetase , complementation , mutant , genetics , activator (genetics) , transcription factor , microbiology and biotechnology , amino acid
Two new yeast genes, named ASN1 and ASN2 , were isolated by complementation of the growth defect of an asparagine auxotrophic mutant. Genetical analysis indicates that these two genes are allelic to the asnA and asnB loci described previously. Simultaneous disruption of both genes leads to a total asparagine auxotrophy, while disruption of asn1 or asn2 alone has no effect on growth under tested conditions. Nucleotide sequences of ASN1 and ASN2 revealed striking similarities with genes encoding asparagine synthetase (AS) from other organisms. Regulation of ASN1 and ASN2 expression was studied using lacZ fusions and both genes were found to be several times less expressed in the absence of the transcription activator Gcn4p. The HAP complex, another transcription factor that binds to CCAAT‐box sequences, was shown to specifically affect ASN1 expression. Hap2p and Hap3p subunits of the HAP complex are required for optimal expression of ASN1 , while the Hap4p regulatory subunit, which is required for regulation by the carbon source, plays a minor role in this process. Consistent with the weak effect of Hap4p, the carbon source does not significantly affect expression of ASN1 . Our results show that the role of the HAP complex is not limited to activation of genes required for respiratory metabolism.