FIG. 7.

HCV RNA abundance in 2-3 cells during serum starvation. (A) Northern blot detection of HCV RNA in clone 2-3 cells grown in medium containing the indicated percentage of serum for 3 days. Total RNA was extracted and hybridized to a probe specific for NS5B. HCV RNA abundance declined with decreasing concentrations in serum. (B) Analysis of HCV RNA synthesis during serum starvation by in vivo labeling. Normal Huh7 cells (lane 1) or clone 2-3 cells (lanes 2 to 5) were incubated in the presence (lanes 1 and 2) or absence of serum for 72 h (lanes 3 to 5). Serum was added back for 48 and 72 h, respectively, after the 72-h period of serum starvation for the samples shown in lanes 4 and 5. HCV RNA synthesis was monitored by incorporation of [³²P]orthophosphate for 15 h, followed by gel electrophoresis and autoradiography of the isolated RNA (top panel). Also shown is the 26S RNA band from the same gel visualized with ethidium bromide (bottom panel). (C) Results of densitometric quantitation of the 2-3 cell data shown in panel B, with values for HCV RNA normalized to the amount of 26S RNA and the values for cells growing in 10% serum set arbitrarily to 100%.