Figure 2.

Expression of Caulobacter tmRNA. (A) Northern blots of total RNA from Caulobacter were probed with oligonucleotides complementary to the tagreading frame (tag) or the acceptor arm (acceptor). The sizes indicated were determined by nuclease protection assays. M, size markers; kb, kilobase. (B) Primer extension assays of total Caulobacter RNA with primers complementary to the tag reading frame (tag), the acceptor arm (acceptor), and the intervening segment (intervening). Each primer extension is electrophoresed next to sequencing reactions performed with the cognate primer, and the local sequence is shown. The two panels for the tag primer are different exposures of the same extension reaction. (C) Schematic summary of primer extension results. The observed abundant (solid lines) and rare (dashed lines) extension products and deduced RNA species are shown relative to the tmRNA gene.