FIG. 4.

Assays of HDV replication in avian and mammalian cells in the presence of tetracycline-controlled expression of small delta protein. Cultures of LMH (lanes 3 to 6) or Huh7 cells (lanes 7 to 10) were cotransfected in the presence of tetracycline with fixed amounts of pGG119, pJC110, and pPB106, expressing the small form of the delta protein under control of tetracycline. Tetracycline was removed after day 1 for 0.5 days (lanes 3 and 7), 3 days (lanes 4 and 8), and 5 days (lanes 5 and 9). Lanes 6 and 10 are untransfected controls. Lane 1 contains 5′-labeled DNA size markers. Lane 2 is a standard of unit-length HDV cDNA (200 pg). At 6 days after transfection, RNA and protein were extracted. RNA was analyzed by Northern blot for antigenomic RNA (A) or genomic RNA (B). Protein was assayed by immunoblot for delta protein (C).