MUTATIONS OF POLYOMAVIRUS VP1 ALLOW IN-VITRO GROWTH IN UNDIFFERENTIATED CELLS AND MODIFY IN-VIVO TISSUE REPLICATION SPECIFICITY

Mutants of polyomavirus with altered host specificities were isolated in undifferentiated C2 myoblast cells (L. Ricci, R. Maione, C. Passana nti, A. Felsani, and P. Amati, J. Virol. 66:7153-7158, 1992). The muta tions responsible for this phenotype belonged to either of the two cla sses: a large duplication of the enhancer region or a 6-bp deletion in the VP1 coding region. Since both classes of mutations enabled the vi rus to grow in undifferentiated myoblast cells, we investigated their ability to replicate in embryonal carcinoma cells and in various tissu es in newborn mice. Our results show that both kinds of mutations conf er the ability to replicate in vitro in embryonal carcinoma F9 cells; the VP1 mutants acquired an in vivo host range of replication which is different from that of their original wild-type strain, whereas the m utation in the regulatory region did not alter the in vivo growth spec trum.