Decreased initiation factor activity in mouse L cells treated with interferon

Mechanism of interferon action: Phosphorylation of protein synthesis initiation factor eIF-2 in interferon-treated human cells by a ribosome-associated kinase processing site specificity similar to hemin-regulated rabbit reticulocyte kinase

“…Interferon-treated intact cells show a reduced ability to support the initiation of viral protein synthesis in vivo (22). In vitro studies with cell-free systems have likewise revealed that the initiation of translation is affected by interferon treatment (23,24,36,37). In the rabbit reticulocyte system, the phosphorylation of eIF-2a is a necessary condition for the inhibition of protein synthesis at the initiation level (7)(8)(9)(10)(11)).…”

“…The inhibition of translation in interferon-treated cell-free systems occurs both at the level of initiation and of elongation of polypeptide chain biosynthesis. The inhibition at the level of initiation, characterized by a reduction in the association of virus mRNA to ribosomes (22) and a reduction in the formation of virus-specific methionyl-X initiation peptides (23), is accompanied by a reduction in protein synthesis eIF-2 activity (24,25). The inhibition at the apparent level of elongation appears to be due, in part, to either the nucleolytic degradation of the viral mRNA (26,27) or to a deficiency of certain minor tRNA species (28,29) or to both.…”

Regulation of Interferon-impaired Initiation Factor Activity in Vitro by cAMP and dsRNA

“…5.50 We have reported that treatment of mouse L cells with homologous interferon results in a reduction in the ability of initiation factor (eIF-2) to bind with initiator tRNA (Met-tRNAf) and GTP (1). In the rabbit reticulocyte lysate-protein synthesizing systems, polypeptide chain initiation is inhibited by a heme-regulated translation inhibitor (HRI) in the presence of ATP.…”

“…The cells treated or untreated with interferon (about 4 X 10' cells) were homogenized in 20 mM Tris-HC1 buffer (pH 7.5) containing 10 mM KCl, 5 mM MgClz and 2 mM dithiothreitol (DTT), then centrifuged for 20 min at 15,000 rpm. Ribosomes in this supernatant were further purified by 60% sucrose cushion gradient centrifugation as previously reported (1). The purified ribosomes were suspended in 10 mM Tris-HC1 (pH 7.5) containing 0.25 M sucrose, 1 mM EDTA, 2 mM DTT and 0.5 M KC1, and then gently stirred for 60 min at 4".…”

“…Initiator tRNA (tRNAf-Met) was purified from rat liver us-ing DEAE-cellulose and BD-cellulose, successively, and then charged with 35S-methionine (22.3 Ci/mmol) using Met-tRNA synthetase purified from Escherichia coli as previously reported (1).…”