Alterations in the distribution of labeled ribonucleic acid in polyribosomes from Escherichia coli infected with bacteriophage R17.

The distribution of labeled ribonucleic acid (RNA) associated with polysomes from Escherichia coli infected with the bacteriophage R17 was investigated. Pulse-labeling of RNA for 15 sec with (3)H-uridine resulted in increased labeling of the RNA associated with larger polysomes from infected cells as compared to control cells. Analysis of the RNA indicated that the increased labeling of large polysomes resulted from the presence of labeled double-stranded viral RNA. Other species of 15-sec pulse-labeled RNA entered into polysome formation in both infected and control cells. On the other hand, pulse-labeling of cultures for 15 sec with (3)H-uridine followed by a 5-min chase with unlabeled uridine resulted in a greater decrease in the amount of labeled RNA associated with large polysomes from infected cells as compared to control cells. This decreased labeling of large polysomes from infected cells was accompanied by an increased amount of label associated with the monomer to trimer regions. Analysis of RNA labeled under pulse-chase conditions indicated that virus infection resulted in an increased amount of heterogeneous 5 to 15S RNA in both the monomer to trimer and ribosomal subunit-soluble regions of the polysome profile. Labeled 5 to 15S RNA extracted directly from infected cells under pulse-chase conditions, without prior polysome fractionation, was characterized by a shift toward a distribution of smaller polynucleotides.