Apparent MRNA Instability in Aspergillus Nidulans and Aspergillus Terreus of a Heterologous CDNA Encoding the Major Capsid Antigen of Rotavirus

Two expression plasmids designed to produce the rotaviral VP6 protein in Aspergillus nidulans and Aspergillus terreus have been constructed. In one of these plasmids the inducible A. terreus Gla1 glucoamylase gene promoter and Gla1 signal sequence are fused to the VP6 cDNA to enable induction and extracellular secretion of the final protein product; in the other, the strong, constitutive A. nidulans gpdA gene promoter has been employed. A. nidulans and A. terreus transformants containing intact copies of these plasmids have been obtained but neither intra- nor extra-cellular VP6 protein was detectable. Northern analysis indicated specific degradation of the VP6 mRNA. This lack of VP6 mRNA stability may be related to fundamental differences between the general structure of Aspergillus mRNA and that of rotavirus, including codon usage and AU/GC ratio.