Open Reading frames There are 4 open reading frames derived from the same strand(the Incomplete strand) S-the 3 polypeptides of the surface antigen(presl, pres2 and S- produced from alternative translation start sites ·C- the core protein P-the polymerase X-a transactivator of viral transcription(and cellular genes?) HBx is conserved in all mammalian(but not avian hepadnaviruses. Though not essential in transfected cells, it is required for infection in vivoThere are 4 open reading frames derived from the same strand (the incomplete + strand) • S - the 3 polypeptides of the surface antigen (preS1, preS2 and S - produced from alternative translation start sites. • C - the core protein • P - the polymerase • X - a transactivator of viral transcription (and cellular genes?). HBx is conserved in all mammalian (but not avian) hepadnaviruses. Though not essential in transfected cells, it is required for infection in vivo. Open Reading Frames