Inhibition of synthesis of ribosomal proteins and of ribosome assembly after infection of L cells with vesicular stomatitis virus

Ribosomal control in RNA virus-infected cells

Viruses are strictly intracellular parasites requiring host cellular functions to complete their reproduction cycle involving virus infection of host cell, viral genome replication, viral protein translation, and virion release. Ribosomes are protein synthesis factories in cells, and viruses need to manipulate ribosomes to complete their protein synthesis. Viruses use translation initiation factors through their own RNA structures or cap structures, thereby inducing ribosomes to synthesize viral proteins. Viruses also affect ribosome production and the assembly of mature ribosomes, and regulate the recognition of mRNA by ribosomes, thereby promoting viral protein synthesis and inhibiting the synthesis of host antiviral immune proteins. Here, we review the remarkable mechanisms used by RNA viruses to regulate ribosomes, in particular, the mechanisms by which RNA viruses induce the formation of specific heterogeneous ribosomes required for viral protein translation. This review provides valuable insights into the control of viral infection and diseases from the perspective of viral protein synthesis.

The inhibition of mouse L-cell 45 S ribosomal RNA processing is a highly uv-resistant property of vesicular stomatitis virus

In mouse L cells infected with vesicular stomatitis virus (VSV), the synthesis of 45 S rRNA and its conversion to 28 S and 18 S rRNA are inhibited during the course of infection. Evidence is presented that the lack of accumulation of stable rRNA species results not only from the decreased transcription and processing of 45 S rRNA, but also from an increased breakdown of pre-rRNA or stable rRNA during processing. In cells prelabeled with [3H]uridine and then infected, the 28 S and 18 S rRNA species remain unaffected. Studies using uv-irradiated VSV indicate that the viral function involved in rRNA synthesis inhibition is slightly more sensitive to uv irradiation than the function involved in processing inhibition. These results suggest that the VSV functions involved in 45 S rRNA synthesis and processing inhibition may be related, or overlapping, but not identical. In cells infected by VSV mutant T1026R1, total RNA synthesis is inhibited, but the distribution of precursor and stable rRNA species remains nearly normal for up to 5 hr after infection. The function of the mutant virus involved in the inhibition of rRNA processing appears to be defective. In mengovirus-infected L cells, 45 S rRNA synthesis, but not processing, is severely inhibited soon after infection, indicating that a decrease in rRNA transcription is not necessarily accompanied by a decrease in processing.