Genetics - Theses

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Type: PhD thesis × Subject: Aspergillus -- Genetics. × Subject: Gene expression × Subject: Genetic regulation ×

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    Molecular characterisation of the structure and regulation of the gatA, lamA and lamB genes of Aspergillus nidulans
    Richardson, Imogen Barbara. (University of Melbourne, 1991)
    The amdR gene of Aspergillus nidulans controls the expression of structural genes needed for utilisation of omega amino acids and lactams. To understand this regulation the regulatory protein and the genes it controls need to be analysed. This thesis presents work on the structure and regulation of three genes of the amdR regulon, the gatA, lamA and lamB genes. The full sequence and structure of the gatA and lamB genes and the 5' sequence and structure of the lamA gene has been determined. Structural features of these are discussed in relation to other filamentous fungal genes. The gatA gene encodes a gamma-amino butyric acid transaminase and shows homology to the equivalent genes from Saccharomyces cerevisiae and Escherichia coli. The lamA promoter has been found to contain two unusual features: a potential Initiator element at the startpoint of transcription and a downstream TATA element. All three of these genes are under the control of the positive regulatory gene, amdR. Binding sites for the amdR protein in the 5' of gatA and between the divergently transcribed lamA and lamB genes have been identified by comparison with the known amdR protein binding region of the coregulated amdS gene. Analysis of the function of these sequences indicates that there is one major binding site in the gatA promoter and between the divergently transcribed lamA and lamB genes. Comparison of these functional sequences and the previously identified site in amdS with the non-functional sites indicates certain bases within the binding sequence which may be important for efficient binding. Three CCAAT factor binding sequences have been found in the gatA and lam promoters. Two of these sequences are closely associated with functional amdR protein binding sites as has also been shown by others to be the case for amdS.