Translational Control in Murine Hepatitis Virus Infection

Abstract

SUMMARYHigh multiplicity infection of mouse fibroblast L-2 cells with mouse hepatitis virus (MHV) resulted, within 6 h, in a decline in total protein synthesis to about 7~ of that observed in uninfected cells. The amount of intracellular total translatable RNA, however, increased approximately threefold, as a result of the accumulation of virusencoded mRNAs. MHV-infected cells could be superinfected with vesicular stomatitis virus, demonstrating that MHV infection did not irreversibly alter the cellular translational machinery to the exclusion of non-MHV mRNAs. Comparative polysome analysis from MHV-infected and uninfected L-2 cells showed that MHV infection resulted in an increase in single 80S ribosomes and in a shift from longer to shorter polysomes. These observations suggest first, that MHV infection inhibits total protein synthesis at a very early stage, as evidenced by the increase in 80S ribosomes, and, second, that the increased number of viral mRNAs produced after infection compete with cellular mRNAs for cellular ribosomes. In vitro translation of RNA extracted from MHV-infected and mock-infected cells suggested that levels of cellular mRNAs were decreased after infection. This suggestion was confirmed by demonstrating the loss of cellular actin mRNA, using a radiolabelled cDNA probe, as a consequence of MHV infection.

A Model for Persistent Murine Coronavirus Infection Involving Maintenance via Cytopathically Infected Cell Centres

“…MHV normally shuts off host cell protein synthesis very effectively in L-2 cells (Hilton et al, 1986). This is apparent in Fig.…”

RNase L-Independent Specific 28S rRNA Cleavage in Murine Coronavirus-Infected Cells

“…Some progress has been made regarding the mechanism of cell death in coronavirus-infected cells; infection of coronavirus transmissible gastroenteritis virus and MHV induces apoptosis in certain cells (1,3,8). As found for some lytic viruses (9,11,20,21), host protein translation is inhibited (12,42,49,50) but not completely shut off in MHV-infected cells. Inhibition of host protein synthesis is accompanied by an increase in MHV protein synthesis (42,43,44).…”

Translational Regulation in Mouse Hepatitis Virus Infection Is Not Mediated by Altered Intracellular Ion Concentrations

“…1). It is therefore unlikely that alterations in intracellular Na+/K + concentrations play a significant role in contributing to the dramatic conversion from host to viral protein synthesis seen in MHV infection (Cheley & Anderson, 1981;Hilton et al, 1986).…”

“…Since MHV infection results in severe inhibition of host cell protein synthesis by 5 to 6 h p.i. (Hilton et al, 1986), cultures were radiolabelled at an earlier time, i.e. from 4-5 to 4.75 h p.i.…”

“…For these studies, the lytic, fusogenic MHV infection of L-2 cells was chosen as a model system since the expression of membrane fusion is much higher than that seen in MHV infections of other cell lines (Mizzen et al, 1983). Moreover, since L-2 cells are highly susceptible to MHV-induced inhibition of host cell protein synthesis (Hilton et al, 1986) they are very well suited to an examination of a possible relationship between membrane ion leakage and translational control in MHV infection.…”