TABLE 2.

CAT activities in lysates of BS-C-1 cells transfected with dicistronic plasmids containing the poliovirus or HAV IRES and expressing either intact PTB or the Δ87-531 null mutant

PTB segment	Mean cpm ± SDa
	Poliovirus 5′NTR	HAV 5′NTR
Δ87-531	2,408 ± 30.6	129 ± 12.1
wtb	28,652 ± 1,167	4,886 ± 202

^aFrozen lysates from multiple experiments were retested in a single CAT assay with 125-μl reaction volumes containing 10 μl of lysate incubated at 37°C for 1 h. The values shown were obtained with cell lysates from four separate transfections carried out in two independent experiments. 

^bpPwt constructs (Fig. 1A).