The Encephalomyocarditis Virus 3C Protease Is Rapidly Degraded by an ATP-Dependent Proteolytic System in Reticulocyte Lysate

A region of the coronavirus infectious bronchitis virus 1a polyprotein encoding the 3C-like protease domain is subject to rapid turnover when expressed in rabbit reticulocyte lysate

“…It is possible therefore that the instability observed is significant in terms of the virus life-cycle, although in the absence of cleavage data or in vivo expression data (the protein has yet to be identified in infected cells) it is not possible to determine fully the relevance of this finding to the control of coronavirus 3C expression and function. However, there is a close parallel between our observations and those of Lawson et al (1994) concerning the low in vitro stability of EMCV 3C protease, which itself accords with the observed in vivo metabolic instability of several viral proteases in the 3C-like group (Oberst et al, 1993). The coronavirus 3C domain may thus exhibit this characteristic feature of the 3C protease family as a conserved trait.…”

“…This is the third reported example of a viral protein subject to turnover in this manner and involves a different virus class to the previously reported examples, in a picornavirus (Oberst et al, 1993) and an alphavirus (de Groot et al, 1991). In addition, the identification of this process adds to the repertoire of regulatory mechanisms potentially used by coronaviruses.…”

“…The property of a degron to function in a context-independent manner may be an important prerequisite for the control of differently processed versions of a polyprotein or to enable regulation of downstream functions whose effectors have yet to be processed from the polyprotein (possibly by 3C). It is of relevance to note here that Oberst et al (1993) reported a hierarchical pattern of stability of different 3C-bearing polyprotein fragments. Thus, the two degrons identified here may both have significant impact upon the cellular levels of ORF 1 products.…”

“…The behaviour of the 205 protein is suggestive of the multiubiquitination that normally occurs prior to degradation of such targeted proteins by an energy-dependent 26S cellular protease complex (Hershko et al, 1984). Since the 205 clone encodes the predicted 3C-tike protease domain of IBV, this observation suggested a correlation with the observed low in vitro stability of the encephalomyocarditis virus (EMCV) 3C protease, which has been attributed to energy-dependent proteolysis (Oberst et al, 1993). We tested the importance of the C terminus in determining the behaviour of the 205 protein by translation of a series of Y-terminally truncated RNA transcripts obtained by run-off transcription of appropriately linearized pKT205 plasmid.…”

The Processing of eIF4GI by Human Rhinovirus Type 2 2A pro : Relationship to Self-Cleavage and Role of Zinc

“…Complete cleavage is achieved between 60 and 90 min. The amounts of VP1 decrease over time, indicating nonspecific degradation of the protein in the lysate; this has been observed for certain proteins expressed in RRLs (21). The band corresponding to 2A pro is less intense than VP1, since it contains only two methionines, compared to the 9 methionines of VP1.…”