TRANSCRIPTIONAL TRANSACTIVATION OF PARVOVIRUS B19 PROMOTERS IN NONPERMISSIVE HUMAN-CELLS BY ADENOVIRUS TYPE-2

The pathogenic human parvovirus B19 contains a promoter at map unit 6 (B19p6) of the viral genome, expression from which is largely restrict ed to human cells in the erythroid lineage, whereas a putative promote r at map unit 44 (B19p44) is inactive during a natural viral infection . Although nonerythroid human cells, such as HeLa and KB, allow expres sion from the B19p6 promoter but not from the B19p44 promoter followin g DNA-mediated transfection, little expression from the B19p6 promoter occurs following recombinant virus infection (S. Ponnazhagan, X.-S. W ang, M. J. Woody, F. Luo, L, Y. Kang, M. L. Nallari, N. C. Munshi, S. Z. Zhou, and A. Srivastava, submitted for publication). However, signi ficant expression from the B19p6 promoter as well as the B19p44 promot er could be detected in a human 293 cell line that expresses the adeno virus early gene products, suggesting that coinfection with adenovirus might mediate transcriptional transactivation of the B19 promoters in nonpermissive cells. Expression of the firefly luciferase reporter ge ne from the B19 promoters was evaluated either following plasmid trans fection or following infection with the recombinant adeno-associated v irus type 2 vectors. Both B19p6 and B19p44 promoters could be transact ivated by coinfection with adenovirus in nonpermissive human cells, al though the extent of transactivation of the B19p44 promoter was signif icantly lower than that of the B19p6 promoter. Expression of the adeno virus E1A proteins was necessary and sufficient for the observed trans activation of the B19 promoters. These studies further illustrate that the underlying molecular mechanisms of transactivation of parvovirus promoters in general by the adenovirus early proteins have similaritie s with those of the well-documented transactivation of the adeno-assoc iated virus type 2 promoters.