FIGURE 1.

The ribosomal protein S1 enhances transcriptional cycling. In vitro transcription reactions with supercoiled DNA template pCPGλtr2 (Reynolds et al. 1992) were carried out as described in Materials and Methods. (A) Kinetics of the transcription-stimulatory activity of S1. Reactions were carried out in the presence or absence of 0.2 μM purified native S1. The position of the T7A1 promoter-generated transcript RNA terminated at a specific transcription terminator (λtr2) is indicated. (B) The yields of T7A1/λtr2 transcript plotted as a function of native S1 concentration. In vitro transcription reactions were carried out in the presence of 50mM NaCl (open symbols) and 100 mM NaCl (closed symbols). (C) The transcription-stimulatory effect of S1 is abolished in the presence of high concentrations of the DNA competitor heparin. The reaction conditions were as described in Materials and Methods, with the exception that heparin was added to some of the reactions along with the rNTP premix. In vitro transcription reactions were performed in the absence (open boxes) or in the presence (solid boxes) of 0.2 μM purified native S1.