Studies on the mechanism for entry of vesicular stomatitis virus glycoprotein g mRNA into membrane-bound polyribosome complexes

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Abstract
Glycoprotein[G).mu.RNA of vesicular stomatitis virus is synthesized in the cytosol fraction of infected [human cervical carcinoma] HeLa cells. Shortly after synthesis, this mRNA associates with 40S ribosomal subunits and then forms 80S monosomes in the cytosol fraction. The bulk of labeled G mRNA is then found in polysomes associated with the membrane, without first appearing in the subunit or monomer pool of the membrane-bound fraction. Inhibition of the initiation of protein synthesis by pactamycin or muconomycin A blocks entry of newly synthesized G mRNA into membrane-bound polysomes. Under these circumstances, labeled G mRNA accumulates in the cytosol. Inhibition of the elongation of protein synthesis by cycloheximide allows entry of 60% of newly synthesized G mRNA into membrane-bound polysomes. Prelabeled G mRNA associated with membrane-bound polysomes is released from the membrane fraction in vivo by pactamycin or muconomycin A and in vitro by 1 mM puromycin-0.5 M KCl. This release is not due to nonspecific effects of the drugs. Association of G mRNA with membrane-bound polysomes is apparently dependent upon polysome formation and initiation of protein synthesis. Direct association of the 3'' end of G mRNA with the membrane does not appear to be the initial event in formation of membrane-bound polysomes.