Effects of metals on the binding of protein factors to the mouse 2',5'-oligoadenylate synthetase ME-12 gene regulatory region

Selective interferon-alpha/beta effects on platelet-derived growth factor-stimulated processes in quiescent BALB/c-3T3 fibroblasts

Interferon-alpha/beta (IFN-alpha/beta) suppresses cell cycle activation by platelet-derived growth factor (PDGF) as well as the induction of the 31-kD (pI) and the 35-kD (pII) proteins in density-arrested BALB/c-3T3 cells. We report that elevation of [Ca2+]i by ionomycin induces the synthesis of the 31-kD protein, but not that of the 35-kD protein. Since IFN blocks the PDGF-induced elevation of [Ca2+]i, these results suggest that IFN treatment may suppress pI induction by impairing this PDGF-activated signal transduction pathway. In contrast, because ionomycin did not induce the 35-kD protein, the suppression by IFN of PDGF-induced pII appears to be mediated via a pathway distinct from that operating in the suppression of pI. In BALB/c-3T3 cells, IFN-alpha/beta did not itself affect the turnover or de novo synthesis of inositol phospholipids and the cellular content of diacylglycerol, nor did IFN block the enhancement of these parameters by PDGF.

Identification of a new interferon-alpha/beta-inducible DNA-binding protein that interacts with the regulatory element A of 2',5'-oligoadenylate synthetase ME-12 gene

A new interferon (IFN)-stimulated response factor (ISRF) has been identified in nuclear extracts of IFN-alpha/beta-treated murine BALB/c-3T3 fibroblasts by the mobility-shift electrophoresis assay. The factor, ISRF-2, displays murine 2',5'-oligoadenylate (2-5A) synthetase ME-12 gene 5' regulatory element A specificity and differs from the previously described IFN response element B-specific factor ISRF-1 in several aspects. ISRF-2 is restricted to the nucleus, whereas ISRF-1 exists in the cytoplasm and translocates into the nucleus upon treatment of cells with IFN-alpha/beta. The ionic strength requirement of ISRF-2 for maximal DNA-binding activity is lower than that of ISRF-1. The DNA-binding activity of ISRF-2, but not that of ISRF-1, is markedly suppressed by Mg2+. In common with ISRF-1, the phosphorylated form of ISRF-2 appears to be required for DNA-binding activity. A model is proposed for the mechanism whereby murine IFN-alpha/beta regulates 2-5A synthetase ME-12 gene expression.

Molecular cloning and characterization of additional factors that bind to the interferon-alpha/beta response element B of the murine (2'-5')oligoadenylate synthetase ME-12 gene

The function of interferon (IFN) response elements (IREs) may be classified into two classes according to the location of the IRE in the polymerase II transcription promoter: located upstream of the core promoter, or located within the core promoter. Thus, the IRE-binding factors (IREBFs) can serve as sequence-specific transcription factors that activate IFN-inducible gene transcription and they can participate in preinitiation complex formation. In the murine and human (2'-5')oligoadenylate synthetase genes the IRE is located within the core promoter region. For this reason, it is important to isolate cDNAs encoding protein factors that can bind to this IRE and determine their functional roles in the regulation of expression of the IFN-inducible (2'-5')oligoadenylate synthetase gene. We have isolated three groups of cDNAs that encode IREBFs. Here we report on clone 38 cDNA, which contains an open reading frame encoding a protein of 277 amino acids that is designated IREBF-2. The C terminus of IREBF-2 is extremely proline-rich and contains a high percentage of short-armed amino acids. IREBF-2 shares marked similarity with some gene products of the herpes group of viruses. These gene products are potent transcription activators. IREBF-2 is constitutively expressed in BALB/c 3T3 cells.