FIG. 3.

Primer extension experiments performed with the PE1 (A) or PE2 (B) oligonucleotides. For (A) two different amounts of COLO 320 (4 and 2 μg) total RNAs were used whereas for (B) COLO 320 and NBE total RNAs were used. Ctrl: Control experiment with in vitro synthetized cold RNA as explained in the text. The sizes of the extended fragments as the three major start sites S1, S2, and S3 are indicated. In (A) the star indicates an artefactual band in the sequencing reaction and the arrowhead indicates the extended product in the control lane.