The 2A proteins of three diverse picornaviruses are related to each other and to the H-rev-107 family of proteins involved in the control of cell proliferation

The 2A protein appears to be diverse among picornaviruses, in contrast to t he other non-structural proteins, which have homologous structures and func tions. In enteroviruses and rhinoviruses, 2A is a trypsin-like protease inv olved in protein processing and in shut-off of host-cell macromolecular syn thesis. The aphthovirus and cardiovirus 2A is associated with an unusual pr ocessing event at the 2A/2B junction. It is shown here that the 2A protein of several diverse picornaviruses, the human parechoviruses, Aichi virus an d avian encephalomyelitis virus, possess previously unrecognized conserved motifs and are likely to have a common function. Moreover, these motifs, a conserved histidine and flanking amino acids, an asparagine-cysteine dipept ide and a putative transmembrane domain, are characteristic of a family of cellular proteins, at least two of which are involved in the control of cel l growth. These observations have important implications for an understandi ng of picornavirus genome structure and evolution, as well as pointing to p ossible functions of 2A in these viruses.