Abnormal behavior of interferon-induced enzymatic activities in an interferon-resistant cell line.

Abstract

Interferon induces two double-stranded RNA-dependent enzymatic activities: an oligoisoadenylate synthetase that converts ATP to ppp(A2'p).5'A, and a protein phosphokinase. We have explored the level and inducibility of these two enzymes in a human cell line (HEC-1) totally insensitive to both the antiviral and the anticellular actions of interferon. The activities of both enzymes are high in untreated cells and only minor changes occur after treatment with interferon, even at high concentrations. Interferon-treated HEC-1 cells do not contain an inhibitor of the oligoisoadenylate synthetase activity. The products of this HEC-1 oligoisoadenylate synthetase consist mainly of dimers, trimers, and tetramers as found in other cell lines after interferon treatment. The synthetase level is unaffected by treating the cells with anti-interferon antiserum, indicating that the results cannot be explained by a spontaneous low production of interferon by these cells. Furthermore, virus multiplication is not inhibited, even after treatment with interferon. These observations suggest that either the two enzymatic activities do not suffice for the establishment of an antiviral state in vivo or that a regulatory control mechanism, lost in these cells and common for both enzymes, is required for the expression of the antiviral action of interferon. This might explain both the constitutivity of the two enzymes and the interferon resistance observed.

Resistance to Interferon of a Human Adenocarcinoma Cell Line, HEC-1, and its Sensitivity to Natural Killer Cell Action

“…In HEC-1 cells, however, these enzymes are both present in untreated cells and are not enhanced by interferon treatment (Verhaegen et al, 1980). HEC-1 cells were also resistant to the cell growth-inhibiting action of HuIFN-¢t.…”

Antiviral, Anticellular and Enzyme-inducing Activities of Interferons in RD-114 Cells

“…This discrepancy could be due to a higher sensitivity of our assay method or due to a genuine difference between the properties of our cell line and those of the subclone of RD-114 line used by them. The 2,5(A) synthetase level in untreated RD-114 cells was very low, unlike the high constitutive level of 2,5(A) synthetase in HEC-1 cells, another human line in which VSV replication is insensitive to IFN (Verhaegen et al, 1980). Although introduction of 2,5(A) into RD-114 cells caused severe inhibition of protein synthesis, presumably through activation of the RNase L pathway, only low levels of RNase L activity could be detected in the cell extracts.…”

2′‐Phosphodiesterase Activity in Human Cell Lines Treated or Untreated with Human Interferon

“…These cell lines present different sensitivities to interferon as far as the antiviral and anticellular effects are concerned. In RSa, IF', WGA' and HeLa cells, (2'-5')(A)n synthetase is normally induced after interferon treatment [23,24], whereas this enzyme is present at a high basic level and not inducible in HEC-1 cells [25]. The results reported here indicate that, in all the human cell lines tested, the 2'-phosphodiesterase activity remains unchanged after interferon treatment even in the four cases where (2'-5')(A), synthetase is normally induced.…”

“…In the former method the samples were further treated with alkaline phosphatase (at a final concentration of 100 U/ml) for 1 h at 37°C. In both cases, 2 4 aliquots were applied to thinlayer sheets of polyethyleneimine (Machery-Nagel) and chromatographied in I M acetic acid as previously described [25]. Thereafter, the sheets were submitted to autoradiography and the radioactivity of the spots corresponding to either remaining [32P](2r-S')(A), or released [32P]AMP was measured in a scintillation counter.…”

“…prepared as follows. The highly active (2'-5')oligo(adenylate) synthetase from cell extracts of interferon-treated HeLa cells was incubated in the presence of [ E -~~P I A T P as previously described [25]. The ["P](2'-5')(A), was isolated by DEAE-cellulose (Whatman DE-52) chromatography and concentrated by acetone precipitation.…”