Posttranscriptional control of human gamma interferon gene expression in transfected mouse fibroblasts.

Abstract

Human gamma interferon genomic DNA was introduced into NIH 3T3 fibroblasts by calcium phosphate precipitation and was not expressed in these cells at the cytoplasmic mRNA or protein level. Treatment of the transfected cells with cycloheximide (1 ,ug/ml) induced the accumulation of cytoplasmic gamma interferon mRNA and biologically active human gamma interferon. Analysis of the nuclear enriched RNA from untreated cells indicated that human gamma interferon mRNA was present, suggesting that cycloheximide may act by inhibiting a specific nuclease or may enhance the processing or transport of the RNA from the nucleus to the cytoplasm.Gamma interferon (IFN-y) is a unique lymphokine which has been reported to have a large number of immunoregulatory functions (for a recent review, see reference 26). Synthesis of this lymphokine appears to be limited to relatively few -cell types, namely T cells and large granular lymphocytes (LGL) (5, 25). Workers in this laboratory have analyzed the expression of the transfected human IFN-y genomic DNA in both a mouse T cell line and NIH 3T3 fibroblasts. It has been found that human IFN-y can be efficiently produced in mouse T cells but is not expressed in transfected mouse fibroblasts at the cytoplasmic RNA or protein level

Regulation of c-myc mRNA stability in vitro by a labile destabilizer with an essential nucleic acid component.

“…The necessity for such precise regulation is consistent with the finding that inappropriate expression of these and other mRNAs and their protein products can interfere with cell replication and differentiation (1,7,12,30,31,39,47). mRNAs whose decay rates seem to be regulated include those expressed from proto-oncogenes (13,15,20,35,41,72); genes related to cell division, including the histones (reviewed in reference 36); acute-phase response and inflammatory response genes (3,19); interferon genes (80); heat shock protein genes (65,71); and developmentally regulated gehes (16,62,73).…”

“…The activity becomes apparent following estrogen withdrawal. (ii) Translation inhibitors induce the accumulation of various mRNAs, a phenomenon frequently referred to as superinduction (3,13,20,35,41,(71)(72)(73)80). Although the mechanism of superinduction is incompletely understood, our in vitro experiments suggest that, in some instances, it might involve inactivation of destabilizer activities.…”

An intronic 10-base-pair deletion in a class II A beta gene affects RNA processing.

“…Recently, it has become apparent that many genes are regulated at the posttranscriptional level (8,24,36). One notable instance involves the immunoglobulin heavy-chain gene.…”

“…These studies indicate that increased levels of immunoglobulin gene expression in plasma cells are dependent upon posttranscriptional mechanisms. Furthermore, the induction of human beta and gamma interferon expression (22,36), the developmental regulation of the psp gene in the mouse parotid gland (33), and the tissue-specific expression of glyceraldehyde 3-phosphate dehydrogenase in rat tissue (21) all appear to be partially controlled by posttranscriptional events.The cis-acting sequences that act posttranscriptionally to regulate gene expression are not known for many of these cases. However, an AT-rich sequence has recently been identified that causes selective mRNA degradation when introduced into the 3' untranslated region of the ,B-globin gene, which normally produces a stable mRNA (32).…”

“…These studies indicate that increased levels of immunoglobulin gene expression in plasma cells are dependent upon posttranscriptional mechanisms. Furthermore, the induction of human beta and gamma interferon expression (22,36), the developmental regulation of the psp gene in the mouse parotid gland (33), and the tissue-specific expression of glyceraldehyde 3-phosphate dehydrogenase in rat tissue (21) all appear to be partially controlled by posttranscriptional events.…”