IDENTIFICATION AND SUBCELLULAR-LOCALIZATION OF A 41 KDA, POLYPROTEIN 1AB PROCESSING PRODUCT IN HUMAN CORONAVIRUS 229E-INFECTED CELLS

The translation products of the human coronavirus (HCV) 229E open read ing frames la and Ib, the polyproteins la and lab, are processed by vi rus-encoded proteinases. One of the key enzymes in this process is a c hymotrypsin-like enzyme, the 3C-like proteinase. In this study we have identified an ORF Ib-encoded, 41 kDa processing product in HCV 229E-i nfeded cells by using a monoclonal antibody with defined specificity. We show that this polypeptide is released from polyprotein lab by 3C-l ike proteinase-mediated cleavage of the peptide bonds Gln-6110/Gly-611 1 and Gln-6458/Ser-6459. Also, we have investigated the subcellular lo calization of the 41 kDa processing product. Immunofluorescence micros copy revealed a punctate, perinuclear distribution of the 41 kDa polyp eptide in infected cells and an identical subcellular localization was observed for three additional pp1ab-derived polypeptides. In contrast , the virus nucleocapsid protein showed a homogeneous cytoplasmic loca lization.