Biochemistry. In the article “Escherichia coli RNA polymerase terminates transcription efficiently at rho-independent terminators on single-stranded DNA templates” by Susan M. Uptain and Michael J. Chamberlin, which appeared in number 25, December 9, 1997, of Proc. Natl. Acad. Sci. USA (94, 13548–13553), the authors request that the following correction be noted. It is critical that the bands in lanes 6 and 8 of Fig. 3 indicated by the T7Te arrow be visible. The existence of these terminated bands is a major point on which the conclusions of the paper depend. Therefore, to enhance their visibility, Fig. 3 and its accompanying legend are reprinted below with greater contrast.

Figure 3.

 Assaying for intrinsic transcript termination at T₇Te on ssDNA. C₄₆ complexes bound to Ni²⁺-NTA agarose in TGK-B₄₀M₄ were chased with 500 μM ATP, 500 μM GTP, 500 μM CTP, and 500 μM UTP for 10 min at 37°C in the presence of rifampicin at 20 μg/ml and yeast Torula RNA at 0.8 mg/ml. The lanes are assigned as for Fig. 2A. The T₇Te terminator is at positions +95 and +96, whereas transcription to the end of the DNA template generates a run-off RNA of +146 nucleotides. C₄₆ complexes in lanes 5–8 were digested with Exo III at 5,000 units/ml for 5 min at 37°C. Unlike C₄₇, some of the C₄₆ complexes failed to resume elongation after treatment with Exo III (see lanes 6 and 7). The mechanism of this inactivation is unknown but similar observations have been made by others (29, 30).