Virus-induced proteins stability

There is a remarkable lack of effect of the virus-induced protease on cellular protein stability. This was measured by two-dimensional gel analysis of cellular proteins, labelled prior to infection. Samples were monitored up to the development of the cytopathic effect (Figure 8). The rapid cleavage of viral proteins is not observed at all with the cellular polypeptides, indicating a hi degree of specificity of the protease, or its sequestration from cellular struct-ures. 

As indicated in Table 2.1, most of the promoters used in plant tissue culture have been based on the constitutive cauliflower mosaic virus (CaMV) 35S promoter. In contrast, inducible promoters have the advantage of allowing foreign proteins to be expressed at a time that is most conducive to protein accumulation and stability. Although a considerable number of inducible promoters has been developed and used in plant culture applications, e.g. [32-37], the only one to be applied thus far for the production of biopharmaceutical proteins is the rice a-amylase promoter. This promoter controls the production of an a-amylase isozyme that is one of the most abundant proteins secreted from cultured rice cells after sucrose starvation. The rice a-amylase promoter has been used for expression of hGM-CSF [10], aranti-trypsin [12, 29, 38, 39] and human lysozyme [30]. 

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