Expression of Interferon‐α and Interferon‐β Genes in Human Lymphoblastoid (Namalwa) Cells

Abstract

Treatment of human lymphoblastoid (Namalwa) cells with Sendai virus induced the coordinate synthesis of both IFN-a and 1FN-P interferon mRNAs. One sub-line of Namalwa cells (WRL) produced no IFN-/3 activity, although IFN-8 mRNA was induced and was associated with polysomes. The IFN-a mRNA was heterogeneous, ranging in size over 1.20-1.35 x lo3 bases, probably because of variation in the size of the transcribale DNA in the a-gene family. The IFN-P mRNA was monodisperse with a size of 1.05 x lo3 bases. The kinetics of accumulation and decay of both IFN-a and IFN-/3 mRNAs, as assessed by hybridization with cDNA probes, were very similar to those of translatable interferon mRNA, as assessed by translation in Xenopus oocytes. Treatment of the cells with butyrate or 5'-bromodeoxyuridine increased the amount of hybridizable IFN-c(and IFN-fi mRNA about 25-fold and 4-fold respectively, again demonstrating coordinate control of IFN-a and IFN-8 production The human interferon-a (IFN-a) and interferon-/3 (IFN-/3) genes are a group of structurally related genes which are induced in cells by a variety of stimuli, including virus infection and treatment with double-stranded RNA. At least 12 nonallelic IFN-a genes have been identified [I], together with a single, more distantly related IFN-/3 gene [2, 3). All the genes are located on chromosome 9, although their precise organization is not known [4]. The IFN-/3 gene is clearly some distance away from any IFN-a genes, since a cloned 36 x 103-base genomic fragment containing the IFN-fi gene does not contain any IFN-a genes [5]. However, the IFN-a genes are probably clustered because clones have been obtained which contain more than one IFN-a gene [I, 6, 71. A mixture of IFN-a and IFN-fi is usually produced when human cells are treated with viruses or double-stranded RNA, the relative proportion of the two interferons depending upon the inducer and the cell type being used [S]. In particular, the widely used human lymphoblastoid cell line Namalwa has been shown to produce a mixture of IFN-a and IFN-B upon treatment with Sendai virus [9]. We have now investigated the expression of the IFN-a and IFN-8 genes in these cells using cloned interferon genes as probes, and have shown that a widely used sub-line of Namalwa cells produces both IFN-(x and IFN-/3 mRNAs, but that although the IFN-fi mRNA is associated with polysomes, no biologically active IFN-/j is produced in cells or by translation of interferon mRNA in oocytes. We have further shown that the amounts of IFN-a and IFN-P mRNA are coordinately controlled, and that both are affected in a similar way by treatment of the cells with butyrate or 5'-bromodeoxyuridine. MATERIALS AND METHODS Cells Two sub-lines of human lymphoblastoid (Namalwa) cells were used in this present work. One, termed Namalwa-WRL, Abbreviations. IFN-c(and IFN-P. interferon-a and interferon-p; NaCl/Cit, 150 mM NaCI, 15 mM sodium citrate.

Induction and regulation of the 26-kDa protein in the absence of synthesis of beta-interferon mRNA in human cells

“…A signal of the (Fig. 5B), we could derive an abundance of 0.5 % which is considerably higher than the value found in virusinduced Namalva cells [28] but similar to the estimation given by Zinn et al [18] for the same MG63 cells.…”

Identification of individual interferon-producing cells by in situ hybridization.

“…Although, in general, a good correlation exists between the amount of mRNA synthesized and the IFN secreted, there has been one report demonstrating the presence of untranslated human IFN-pB mRNA in induced Namalwa cells belonging to a particular clone (18). This, however, is not necessarily a disadvantage of in situ hybridization, because this technique could also help to identify cells in which IFN mRNA is transcribed but not translated.…”

Repression of Beta Interferon Gene Expression in Virus-Infected Cells Is Correlated with a Poly(A) Tail Elongation

“…Our results are consistent with the idea that IFN-␤ mRNA with a relatively long poly(A) tail is translated inefficiently if at all. Several cell lines which produce long IFN-␤ transcripts and relatively little IFN-␤ protein have been described (14,21,46,48). However, some of these longer IFN-␤ transcripts may be attributed to alternative usage of poly(A) addition sites (41).…”