PROTEOLYTIC PROCESSING IN AFRICAN SWINE FEVER VIRUS - EVIDENCE FOR A NEW STRUCTURAL POLYPROTEIN, PP62

We have identified an open reading frame (ORF), CP530R, within the Ecc oRI C' fragment of the African swine fever virus (ASFV) genome that en codes a polyprotein of 62 kDa (pp62), Antisera raised against differen t regions of ORF CP530R recognized a polypeptide of 62 kDa in ASFV-inf ected cells during the late phase of virus replication, after the onse t of viral DNA synthesis, Pulse-chase experiments showed that polyprot ein pp62 is posttranslationally processed to give rise to two proteins of 35 kDa (p35) and 15 kDa (p15), This proteolytic processing was fou nd to take place at the consensus sequence Gly-Gly-X through an ordere d cascade of proteolytic cleavages like that which also occurs with AS FV polyprotein pp220 (C. Simon-Mateo, G. Andres, and E. Vinuela, EMBO J. 12:2977-2987, 1993), Immunofluorescence studies showed that polypro tein pp62 is localized in the viral factories, In addition, immunoprec ipitation analysis of purified virus particles showed that mature prod ucts p35 and p15 are major structural proteins, According to these res ults, polyprotein processing represents an essential strategy for the maturation of ASFV structural proteins.