TABLE 2.

In vivo H-19B N-mediated antitermination assays

The ratios of β-galactosidase activities in the presence (+ter) and absence (−ter) of terminators give the values of terminator read-through (%RT), which is a measure of antitermination efficiencies. Rho-dependent (P_lac-H-19B t_R1-trpt′-lacZYA; columns 1 and 2) and -independent (P_lac-H-19B nutR-T_R′-T1-T2-lacZYA; columns 3 and 4) terminator cassettes were fused to the lacZ reporter for the assays. The Rho-dependent terminator, t_R1 was derived from the nutR-cro region of phage H-19B. Measurements were performed both in the absence (−H-19B N) and presence (+H-19B) of N proteins. The errors are calculated from the average of 4–9 independent measurements.

nusA alleles	1 +H-19B N β-galactosidase activity			2 −H-19B N β-galactosidase activity			3 +H-19B N β-galactosidase activity			4 −H-19B N β-galactosidase activity
	+tR1-trpt′	−tR1-trpt′	%RT	+tR1-trpt′	−tR1-trpt′	%RT	+TR′-T1-T2	−TR′-T1-T2	%RT	+TR′-T1-T2	−TR′-T1-T2	%RT
		Arbitrary units			Arbitrary units			Arbitrary units			Arbitrary units
WT	567 ± 16	933 ± 23	61	19 ± 3	1014 ± 30	1.9	424 ± 26	927 ± 44	46	1.0 ± 0.24	130 ± 6	1.0
ΔAR2	326 ± 14	680 ± 26	48	25 ± 2	1075 ± 51	2.3	423 ± 16	813 ± 12	52	2.0 ± 0.15	143 ± 20	1.4
ΔAR1–2	475 ± 15	913 ± 10	52	16 ± 2	1066 ± 25	1.5	338 ± 6	805 ± 56	42	3.0 ± 0.61	148 ± 6	1.7