Posttranscriptional and Transcriptional Regulation of Ribosomal RNA Synthesis in Adenovirus-Infected Cells

Posttranscriptional and Transcriptional Regulation of Ribosomal RNA Synthesis in Adenovirus-Infected Cells 

The production of cytoplasmic 18 S rRNA is also disrupted in adenovirus-infected cells but, as illustrated in Fig. 6, no change is observed until later than 8 hr after infection, and inhibition is not complete until 24 hr after infection. The exact timing of these events is variable and influenced by the multiplicity of infection, but the pattern of inhibition of 28 S relative to that of 18 S rRNA is perfectly reproducible. The inhibition of appearance in the cytoplasmic of 18 S rRNA takes place during the period of inhibition of cellular protein synthesis (see Section 5). The production of such nucleolar pre-rRNA species as 41 S and 32 S rRNA also declines at this time, and by 16 hr after infection a reduction in the synthesis of 45 S pre-rRNA can be detected (Castiglia and Flint, 1983). These later changes in rRNA metabolism in adenovirus-infected cells resemble those reported when cellular protein synthesis is inhibited. The addition of cyclo-heximide, for example, induces a more rapid inhibition of processing 

---