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J. Virol., 12 1995, 7453-7460, Vol 69, No. 12
A Irurzun, S Sanchez-Palomino, I Novoa and L Carrasco
Addition of monensin or nigericin after poliovirus entry into HeLa cells
prevents the inhibition of host protein synthesis by poliovirus. The
infected cells continue to synthesize cellular proteins at control levels
for at least 8 h after infection in the presence of the ionophore. Cleavage
of p220 (gamma subunit of eukaryotic initiation factor 4 [eIF-4 gamma]), a
component of the translation initiation factor eIF-4F, occurs to the same
extent in poliovirus-infected cells whether or not they are treated with
monensin. Two hours after infection there is no detectable intact p220, but
the cells continue to translate cellular mRNAs for several hours at levels
similar to those in uninfected cells. Nigericin or monensin prevented the
arrest of host translation at all the multiplicities of poliovirus
infection tested. At high multiplicities of infection, an unprecedented
situation was found: cells synthesized poliovirus and cellular proteins
simultaneously. Superinfection of vesicular stomatitis virus-infected HeLa
cells with poliovirus led to a profound inhibition of vesicular stomatitis
virus protein synthesis, while nigericin partially prevented this blockade.
Drastic inhibition of translation also took place in influenza
virus-infected Vero cells treated with nigericin and infected with
poliovirus. These findings suggest that the translation of newly
synthesized mRNAs is dependent on the integrity of p220, while ongoing
cellular protein synthesis does not require an intact p220. The target of
ionophore action during the poliovirus life cycle was also investigated.
Addition of nigericin at any time postinfection profoundly blocked the
synthesis of virus RNA, whereas viral protein synthesis was not affected if
nigericin was added at 4 h postinfection. These results agree well with
previous findings indicating that inhibitors of phospholipid synthesis or
vesicular traffic interfere with poliovirus genome replication. Therefore,
the action of nigericin on the vesicular system may affect poliovirus RNA
synthesis. In conclusion, monensin and nigericin are potent inhibitors of
poliovirus genome replication that prevent the shutoff of host translation
by poliovirus while still permitting cleavage of p220.
Copyright © 1995, American Society for Microbiology
Monensin and nigericin prevent the inhibition of host translation by poliovirus, without affecting p220 cleavage
Centro de Biologia Molecular, Universidad Autonoma de Madrid-CSIC, Spain.
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