Figure 4.

Binding of La protein to B2 RNA transcripts of different sizes. Plasmid DNA containing B2 DNA was digested with different enzymes (see text) and transcribed in vitro to produce run-off transcripts of different sizes. (A) These RNAs and GTP were used in immunoprecipitation reactions with the La protein. The bound RNAs were measured by scintillation counting and percentage of the total RNA precipitated was plotted for each transcript of different size. The plots are an average of three independent experiments. (B) Equal counts of the different transcripts and pppG were mixed together. This mixture was immunoprecipitated using the La protein and bound RNAs were purified. These purified RNAs were fractionated on a 10% denaturing polyacrylamide gel (lane 2) along with 5% of the starting RNA mixture (lane 1) and subjected to autoradiography.