PICORNAVIRUS 2A PROTEINASE-MEDIATED STIMULATION OF INTERNAL INITIATION OF TRANSLATION IS DEPENDENT ON ENZYMATIC-ACTIVITY AND THE CLEAVAGE PRODUCTS OF CELLULAR PROTEINS

Poliovirus and human rhinovirus 2A proteinases are known to stimulate translation initiation on the cognate viral Internal Ribosome Entry Se gments (IRESes). The molecular mechanism of this translational transac tivation was investigated in vitro using dicistronic mRNAs containing picornaviral IRESes as the intercistronic spacer and purified human rh inovirus type 2 and coxsackievirus B4 2A proteinases. The stimulation achieved on the HRV2 IRES in the presence of the cognate 2A proteinase at 1 mu g/ml was twofold; the maximum stimulation at 100 mu g/ml was fivefold. The IRESes and proteinases from rhino- and enteroviruses wer e interchangeable; however, stimulation of translation initiation on a cardiovirus IRES by these proteinases was minimal. Studies using an i nhibitor or a mutant 2A proteinase demonstrated that translation stimu lation requires PA-mediated enzymatic conversion of some cellular comp onent(s). The HRV2 2A proteinase also stimulated translation initiatio n on full-length viral RNA, suggesting that 2A proteinase-mediated sti mulation of IRES-driven translation has a physiological role. (C) 1995 Academic Press, Inc.