Expression of the native alpha and beta interferon genes in human cells

Efficient eradication of hormone-resistant human prostate cancers by inactivated Sendai virus particle

Hormone-refractory prostate cancer is one of the intractable human cancers in the world. Here, we examined the direct tumor-killing activity of inactivated Sendai virus particle [hemagglutinating virus of Japan envelope (HVJ-E)] through induction of Type I interferon (IFN) in the hormone-resistant human prostate cancer cell lines PC3 and DU145. Preferential binding of HVJ-E to PC3 and DU145 over hormone-sensitive prostate cancer cell and normal prostate epithelium was observed, resulting in a number of fused cells. After HVJ-E treatment, a number of IFN-related genes were up-regulated, resulting in Type I IFN production in PC3 cells. Then, retinoic acid-inducible gene-I (RIG-I) helicase which activates Type I IFN expression after Sendai virus infection was up-regulated in cancer cells after HVJ-E treatment. Produced IFN-alpha and -beta enhanced caspase 8 expression via Janus kinases/Signal Transducers and Activators of Transcription pathway, activated caspase 3 and induced apoptosis in cancer cells. When HVJ-E was directly injected into a mass of PC3 tumor cells in SCID (severe combined immunodeficiency) mice, a marked reduction in the bulk of each tumor mass was observed and 85% of the mice became tumor-free. Although co-injection of an anti-asialo GM1 antibody with HVJ-E into each tumor mass slightly attenuated the tumor suppressive activity of HVJ-E, significant suppression of tumor growth was observed even in the presence of anti-asialo GM1 antibody. This suggests that natural killer cell activation made small contribution to tumor regression following HVJ-E treatment in hormone-resistant prostate cancer model in vivo. Thus, HVJ-E effectively targets hormone-resistant prostate cancer by inducing apoptosis in tumor cells, as well as activating anti-tumor immunity.

Tumour necrosis factor-induced cytotoxicity is accompanied by intracellular mitogenic signals in ME-180 human cervical carcinoma cells

Tumour necrosis factor-alpha (TNF) induced a cytotoxic response in ME-180 human cervical carcinoma cells in vitro. This cytotoxic response was accompanied by a temporal series of intracellular signals that are commonly triggered by a mitogenic stimulus: increased c-fos (20-30 min) and c-myc (40-60 min) expression, increased activity of ornithine decarboxylase (3 h), increased intracellular polyamine content (7 h) and increased thymidine incorporation into DNA (14 h). A cytotoxic response independent of these mitogenic signals could not be explained by an induction of interleukin-6, which is an autocrine cytotoxic agent in some cell types; nor by a biphasic, dose-dependent response in which low concentrations of TNF are mitogenic and higher concentrations are cytotoxic. Conversely, a dependent role of these mitogenic signals was suggested by the absence of a TNF-promoted increase in thymidine incorporation into DNA in an ME-180 clone that is resistant to TNF-induced cytotoxicity. A decrease in the proliferation rate of TNF-sensitive cells induced by either alpha-difluoromethylornithine treatment (resulting in polyamine depletion) or serum starvation rendered the cells insensitive to TNF-induced cytotoxicity, further suggesting a role for mitogenic signals and cell division in TNF-mediated cytotoxicity. However, inhibiting proliferation with cycloheximide resulted in increased sensitivity to TNF, implying that mitogenesis itself was not essential for a cytotoxic response. TNF induced DNA fragmentation in sensitive cells, suggesting that cytotoxicity occurred via apoptosis.

Translocation (2;9)(p12;p23) in a case of acute leukemia with t(4;11)(q21;q23). Lack of rearrangement of the kappa and interferon gene loci

A case is reported of an adult male patient with acute leukemia characterized by the presence of the novel cytogenetic abnormality, t(2;9)(p12;p23), in addition to a t(4;11)(q21;q23). The immunophenotype of the blast cell population was consistent with immature early pre-B cell acute lymphoblastic leukemia (ALL) (TdT+,HLA-DR+,CD19+,CD24 +/-,CD10-) expressing myelo-monocytic antigens (CDw65,CD15). The genotype showed a clonal rearrangement of the immunoglobulin heavy chain locus. Because the immunoglobulin kappa (kappa) light chain gene is located on chromosome 2 at band p12 and interferon alpha (alpha) and beta (beta) map to chromosome 9p21-p22, rearrangements of these loci as a result of the t(2;9) were studied. There was no evidence for rearrangement of the region covering about 40 kilobases around the kappa locus when hybridized to C(kappa), the 3' kappa enhancer or the kappa deleting element. Only germline size restriction fragments were also found for the interferon alpha and beta genes. The patient's clinical features were typical for ALL associated with the t(4;11), including a high white blood cell count at presentation, hepatosplenomegaly, and a poor outcome. The potential significance of 2p and 9p abnormalities in addition to t(4;11) is discussed.

Activation of 2',5'-oligoadenylate synthetase activity on induction of HL-60 leukemia cell differentiation

A 27-fold increase in 2',5'-oligoadenylate synthetase activity, an enzyme associated with the antiproliferative actions of interferon (IFN), was observed after treatment of HL-60 human leukemia cells with dimethyl sulfoxide (DMSO), an inducer of granulocytic differentiation of the cells. Enzyme activity was elevated after 24 h of exposure to DMSO, was maximal at 48 hours, and declined thereafter. A comparable increase was observed after treatment with 1 U of alpha interferon (IFN-alpha) per ml or 8 U of beta interferon (IFN-beta) per ml. Elevated levels of expression of other IFN-inducible genes, including type I histocompatibility antigen (HLA-B) mRNA and 2',5'-oligoadenylate phosphodiesterase activity, were also observed with DMSO treatment. DMSO-treated HL-60 cells had an increased amount of a 1.8-kilobase mRNA for oligoadenylate [oligo(A)] synthetase when compared with that of control cells; both DMSO- and IFN-treated HL-60 cells also expressed 1.6-, 3.4-, and 4.3-kilobase mRNA. The increase in both oligo(A) synthetase activity and mRNA levels was inhibited by polyclonal antiserum to human IFN-alpha; however, no IFN-alpha mRNA could be detected in the cells. Antiserum to IFN-beta or gamma interferon (IFN-gamma) had no effect on oligo(A) synthetase expression or activity nor was there any detectable IFN-beta 1 or IFN-beta 2 mRNA in the cells. The anti-IFN-alpha serum did not block the elevation of HLA-B mRNA in DMSO-treated cells. These observations suggest that the increased expression of oligo(A) synthetase in DMSO-treated cells may be mediated by the release of an IFN-alpha-like factor; however, the levels of any IFN-alpha mRNA produced in the cells were extremely low.

Activation of 2',5'-oligoadenylate synthetase activity on induction of HL-60 leukemia cell differentiation

A 27-fold increase in 2',5'-oligoadenylate synthetase activity, an enzyme associated with the antiproliferative actions of interferon (IFN), was observed after treatment of HL-60 human leukemia cells with dimethyl sulfoxide (DMSO), an inducer of granulocytic differentiation of the cells. Enzyme activity was elevated after 24 h of exposure to DMSO, was maximal at 48 hours, and declined thereafter. A comparable increase was observed after treatment with 1 U of alpha interferon (IFN-alpha) per ml or 8 U of beta interferon (IFN-beta) per ml. Elevated levels of expression of other IFN-inducible genes, including type I histocompatibility antigen (HLA-B) mRNA and 2',5'-oligoadenylate phosphodiesterase activity, were also observed with DMSO treatment. DMSO-treated HL-60 cells had an increased amount of a 1.8-kilobase mRNA for oligoadenylate [oligo(A)] synthetase when compared with that of control cells; both DMSO- and IFN-treated HL-60 cells also expressed 1.6-, 3.4-, and 4.3-kilobase mRNA. The increase in both oligo(A) synthetase activity and mRNA levels was inhibited by polyclonal antiserum to human IFN-alpha; however, no IFN-alpha mRNA could be detected in the cells. Antiserum to IFN-beta or gamma interferon (IFN-gamma) had no effect on oligo(A) synthetase expression or activity nor was there any detectable IFN-beta 1 or IFN-beta 2 mRNA in the cells. The anti-IFN-alpha serum did not block the elevation of HLA-B mRNA in DMSO-treated cells. These observations suggest that the increased expression of oligo(A) synthetase in DMSO-treated cells may be mediated by the release of an IFN-alpha-like factor; however, the levels of any IFN-alpha mRNA produced in the cells were extremely low.

Signal transduction pathways in the induction of 2',5'-oligoadenylate synthetase gene expression by interferon alpha/beta

Treatment of quiescent BALB/c mouse 3T3 cells with murine interferon alpha/beta (IFN-alpha/beta) (1000 units/ml) leads to the appearance at 4 hr of 1.7-kilobase 2',5'-oligoadenylate (2',5'-OAS)mRNA as detected by Northern blot analysis. This mRNA accumulates for at least 18 hr. Two protein kinase C activators, 1,2-dioctanoyl glycerol and phorbol 12-myristate 13-acetate, suppress, whereas the calcium ionophore ionomycin enhances, the IFN-alpha/beta-induced expression of 2',5'-OAS mRNA. The 8-bromo and dibutyryl analogs of cAMP and the adenylate cyclase activator forskolin did not affect the induction of 2',5'-OAS mRNA by IFN-alpha/beta. In the absence of IFN-alpha/beta, the above agents used either singly or in combinations, did not induce 2',5'-OAS mRNA expression nor did platelet-derived growth factor (1-2 units/ml), fibroblast growth factor (6-100 ng/ml), or bovine serum (10-20%). Bovine serum also did not affect 2',5'-OAS mRNA induction by IFN-alpha/beta. The poly(ADP)-ribose synthetase inhibitor 3-aminobenzamide suppressed IFN-alpha/beta-induced 2',5'-OAS gene expression. These results suggest that in quiescent BALB/c 3T3 cells (i) the 2',5'-OAS gene is not responsive to the three major signal transduction pathways activated by diacylglycerol, Ca2+, and cAMP; (ii) induction of the 2',5'-OAS gene by IFN-alpha/beta is decreased by activation of the protein kinase C pathway but enhanced by elevation of intracellular [Ca2+].

Human fibroblast but not lymphoid cells have unusually long polyadenylated interferon-beta 1 mRNAs

The transcription unit of human interferon-beta 1 (IFN-beta 1) mRNA was examined by chain elongation of nascent RNA in isolated nuclei of human fibroblasts and lymphoid cells induced to produce IFN. In fibroblasts, transcription proceeds beyond 2,400 nucleotides downstream from the poly(A) site of mature mRNA and appears to terminate in the region rich in Alu sequences. Northern hybridization showed the presence of a minor polyadenylated RNA species, about 3,200 nucleotides long, that hybridized to the probes derived from 3'-flanking regions of IFN-beta 1 mRNA. S1 nuclease analysis established that this long polyadenylated transcript represents a mixture of three RNA molecules with defined 3' termini. In all three mRNAs, as in mature IFN-beta 1 mRNA, the polyadenylation site was located within a few nucleotides downstream from the AAUAAA hexanucleotide consensus sequence. Surprisingly, in Namalva lymphoblastoid cells no transcription beyond the polyadenylation site of mature IFN-beta 1 mRNA could be detected either in isolated nuclei or total RNA.

Rapid enhancement of beta 2-interferon/B-cell differentiation factor BSF-2 gene expression in human fibroblasts by diacylglycerols and the calcium ionophore A23187

The expression in human fibroblasts of the beta 2-interferon (IFN-beta 2) gene, which is now recognized to be identical to the gene encoding B-cell differentiation factor BSF-2, is enhanced by several cytokines that affect cell growth (tumor necrosis factor, interleukin 1, platelet-derived growth factor, and beta 1-interferon). We have examined the possibility that IFN-beta 2 gene expression is regulated through activation, by diacylglycerol, of the protein kinase C pathway. The synthetic diacylglycerols 1,2-dioctanoylglycerol (diC8) and 1-oleoyl-2-acetylglycerol strongly enhanced IFN-beta 2, but not IFN-beta 1, gene expression in human fibroblasts (FS-4 strain). An increase in IFN-beta 2 mRNA level was detected within 15 min after addition of diC8 (290 microM) to FS-4 cells and was maximal approximately 20 hr later. An increase in IFN-beta 2 gene transcription was detected within 5 min of addition of diC8, and the rate of transcription was near-maximal by 15-30 min. The enhancement of IFN-beta 2 gene expression by diC8, interleukin 1, or tumor necrosis factor was not prevented by H8, a preferential inhibitor of cAMP- and cGMP-dependent protein kinases, but was blocked by H7, an inhibitor of protein kinase C as well as of cyclic nucleotide-dependent protein kinases. diC8 was found to protect FS-4 cells from the cytopathic effect of vesicular stomatitis virus; this protection was blocked by polyclonal or monoclonal antibodies that neutralize IFN-beta, suggesting that the antiviral effect was due to the secretion of IFN-beta 2 by the diC8-treated fibroblasts. The calcium ionophore A23187 (1-10 microM) also elicited an increase in the level of IFN-beta 2 mRNA in FS-4 fibroblasts; appropriate combinations of A23187 and diC8 had at least an additive effect in enhancing IFN-beta 2 mRNA levels. These results show that protein kinase C-activating or [Ca2+]-elevating agents rapidly increase the expression of the IFN-beta 2 gene in human fibroblasts.

A cytokine network in human diploid fibroblasts: interactions of beta-interferons, tumor necrosis factor, platelet-derived growth factor, and interleukin-1

Earlier studies demonstrated the induction of beta 2-interferon (IFN-beta 2) in human diploid fibroblasts (FS-4 strain) exposed to tumor necrosis factor (TNF). These studies suggested that IFN-beta 2 mediates an antiviral effect in TNF-treated cells and exerts a feedback inhibition of the mitogenic effect of TNF. Here we demonstrate that the expression of the antiviral action of TNF can be enhanced by prior exposure of FS-4 cells to trace amounts of IFN-beta 1. IFN-beta 1, at a higher concentration, can directly increase the expression of IFN-beta 2. Exposure of cells to TNF enhanced IFN-beta 2 (but not IFN-beta 1) mRNA expression in response to poly(I).poly(C), an IFN inducer which is also known to stimulate FS-4 cell growth. Platelet-derived growth factor and interleukin-1 also led to the increased expression of IFN-beta 2. However, platelet-derived growth factor and interleukin-1 could override the antiviral effect of TNF and also that of exogenously added IFN-beta 1. Our data suggest that a complex network of interactions that involves the endogenous production of IFN-beta 2 is triggered by several growth-modulatory cytokines. Cellular homeostasis is likely to represent a balance between the induction of IFN-beta 2 by these cytokines and their ability to override the inhibitory actions of IFN-beta 2.

A cytokine network in human diploid fibroblasts: interactions of beta-interferons, tumor necrosis factor, platelet-derived growth factor, and interleukin-1

Earlier studies demonstrated the induction of beta 2-interferon (IFN-beta 2) in human diploid fibroblasts (FS-4 strain) exposed to tumor necrosis factor (TNF). These studies suggested that IFN-beta 2 mediates an antiviral effect in TNF-treated cells and exerts a feedback inhibition of the mitogenic effect of TNF. Here we demonstrate that the expression of the antiviral action of TNF can be enhanced by prior exposure of FS-4 cells to trace amounts of IFN-beta 1. IFN-beta 1, at a higher concentration, can directly increase the expression of IFN-beta 2. Exposure of cells to TNF enhanced IFN-beta 2 (but not IFN-beta 1) mRNA expression in response to poly(I).poly(C), an IFN inducer which is also known to stimulate FS-4 cell growth. Platelet-derived growth factor and interleukin-1 also led to the increased expression of IFN-beta 2. However, platelet-derived growth factor and interleukin-1 could override the antiviral effect of TNF and also that of exogenously added IFN-beta 1. Our data suggest that a complex network of interactions that involves the endogenous production of IFN-beta 2 is triggered by several growth-modulatory cytokines. Cellular homeostasis is likely to represent a balance between the induction of IFN-beta 2 by these cytokines and their ability to override the inhibitory actions of IFN-beta 2.

Anti-beta-interferon antibodies inhibit the increased expression of HLA-B7 mRNA in tumor necrosis factor-treated human fibroblasts: structural studies of the beta 2 interferon involved

Recombinant Escherichia coli-derived human tumor necrosis factor (TNF) induces the 1.3-kilobase beta 2 interferon (IFN-beta 2) mRNA in human diploid fibroblasts (FS-4 strain). IFN-beta 2 is serologically related to the well-characterized IFN-beta 1 (respective antisera cross-neutralize the heterologous protein). Polyclonal and monoclonal anti-IFN-beta antibodies inhibit the increase in class I HLA gene expression (HLA-B7 mRNA) in TNF-treated FS-4 cells suggesting that TNF-induced IFN-beta 2 mediates the enhancing effect of TNF on HLA gene expression in human fibroblasts. The structure of this autocrine human interferon has been determined. A cDNA library was prepared from polyadenylylated RNA extracted from TNF-induced FS-4 cells, and eight IFN-beta 2 cDNA clones were isolated using a 21-nucleotide synthetic oligonucleotide probe. The 1128-nucleotide sequence of IFN-beta 2 mRNA and the 212-amino acid sequence of the IFN-beta 2 protein were deduced from these cDNA clones. The amino acid sequences of the serologically related human IFN-beta 1 and -beta 2 were compared using the Sellers TT metric algorithm for locating similarities and using the pattern scoring method for evaluating the observed similarities. IFN-beta 1 and -beta 2 each contain a segment that is approximately 100 amino acids including 39 amino acids that are aligned and identical in the two proteins. The hydropathic index plots across these segments in the two proteins are also strikingly similar. The region of similarity between IFN-beta 1 and -beta 2 includes a section that is also highly conserved in all IFN-alpha species sequenced. Thus IFN-beta 2 shares structural similarities with other human interferons that also preferentially increase class I HLA gene expression.

Induction of beta 2-interferon by tumor necrosis factor: a homeostatic mechanism in the control of cell proliferation

Earlier studies showed that tumor necrosis factor (TNF) exerts a mitogenic effect in human diploid fibroblasts. Here we demonstrate that purified E. coli-derived recombinant human TNF inhibits encephalomyocarditis virus replication in "aged" human fibroblasts. Addition of neutralizing antibodies to human beta interferon (IFN-beta) blocked the antiviral action of TNF, indicating that this action is mediated by the generation of IFN-beta. We also show that antiserum to IFN-beta enhanced the mitogenic effect of TNF in confluent, serum-starved human fibroblasts, suggesting that induction of IFN-beta by TNF represents a physiological negative feedback mechanism regulating cell proliferation. Blot hybridization analysis of cytoplasmic polyadenylated RNA showed that TNF induced IFN-beta 2 mRNA, whereas no induction of IFN-beta 1 mRNA could be demonstrated. The results suggest that IFN-beta 2 has biological functions distinct from the other interferons.

Interferon-beta-related DNA on human chromosome 4

A DNA subclone (pPE-4000) derived from the lambda B4 interferon-beta-related human genomic DNA clone was used as a probe in blot-hybridization experiments of DNA from a panel of human-rodent somatic cell hybrids containing overlapping subsets of human chromosomes. The DNA hybridization experiments showed that the lambda B4 IFN-beta locus is localized to human chromosome 4. A provisional regional assignment to 4q12-qter was also obtained. Thus available hybridization data implicate human chromosomes 2, 4, and 9 in the human IFN-beta system while the available biological data also implicated human chromosome 5.

On the relationship between human interferon alpha 1 and beta 1 genes

The human interferon alpha 1 and beta 1 (IFN-alpha 1 and -beta 1) genes are approximately 56% identical in the nucleotide sequence across the regions coding for the mature proteins. An IFN-alpha 1 cDNA insert containing such sequences can be used to isolate 15 IFN-beta 1 cDNA colonies present in a 2600-strong library in Escherichia coli prepared from polyadenylated RNA extracted from human diploid fibroblasts (FS-4) induced with poly(I).poly(C). Conversely, a clone containing an IFN-alpha 1 cDNA exhibited detectable hybridization with an IFN-beta 1 probe. One of the IFN-beta 1 cDNA clones isolated in these experiments had lost the internal PstI and PvuII sites due to a change at nucleotide 277 from a C to an A. As a consequence, this allele codes for Met-47 instead of Leu-47. Suggestive evidence has been obtained for the presence of this allele in human genomic DNA (IFN-beta 1 Met-47).

Differential regulation of interferon synthesis in lymphoblastoid cells

We have examined the molecular mechanisms involved in the induction and regulation of expression of alpha and beta 1 human interferons (HuIFN) in Namalva cells. Cloned IFN-alpha and -beta 1 cDNAs, and antisera to purified IFN-alpha and -beta 1 were used as specific probes to determine the expression of HuIFN genes both on the RNA and protein levels. The rates of gene transcription were correlated with the relative levels of HuIFN mRNA present in induced cells and with the amounts of HuIFN peptides synthesized by these cells. The comparative rate of transcription of HuIFN-alpha and -beta 1 genes was measured in nuclei isolated from Namalva cells before and after induction. No transcription of HuIFN-alpha and -beta 1 genes was detected in nuclei isolated from the uninduced cells. The correspondence in the rate of HuIFN-alpha and -beta 1 genes transcription after virus infection with the relative levels of HuIFN mRNA in the induced cells indicates that the stimulation of HuIFN synthesis by viral infection results from the activation of the transcription of HuIFN genes. The relative levels of alpha and beta 1 induced transcripts were the same in spite of the differences in the number of copies of HuIFN-alpha and -beta 1 genes indicating that the beta 1 gene is transcribed more efficiently than the alpha genes. The steady-state levels of HuIFN-alpha and -beta 1 mRNAs in induced Namalva cells are comparable, however, the overall amount of HuIFN-beta 1 synthesized (as determined by radioimmunoassay and biological activity) is approximately 10-fold lower than that of IFN-alpha. No evidence has been found that would indicate that HuIFN-beta 1 mRNA induced in Namalva cells is different from that induced in human fibroblasts. The data indicate, however, that in Namalva cells, the IFN-beta 1 polypeptide has a higher turnover rate and slower rate of release into medium than the HuIFN-alpha polypeptides, indicating that the observed difference in the overall amounts of these two types of interferons present in the medium is due to regulation on posttranslational level.

Increased nuclease sensitivity of the human interferon-alpha 1-related genes and the interferon-beta 1 gene during induction by virus

The chromatin structure of the human interferon (IFN) genes was evaluated during induction of human lymphoblastoid (Namalwa) cells by Sendai virus. Namalwa cells were treated with bromodeoxyuridine (BrdUrd) for 36-48 h and induced with Sendai virus for 7 h; the nuclear fraction was isolated and treated with low levels of either micrococcal nuclease or DNAse I. DNA was extracted from the nuclease-treated chromatin, restricted with Eco RI and analyzed by Southern blotting using IFN-alpha 1 and -beta 1 cDNA probes. An increase in the digestibility of the IFN-alpha 1-related genes and the IFN-beta 1 gene was observed in chromatin prepared from BrdUrd-treated, Sendai virus-induced Namalwa cells as compared with chromatin from uninduced Namalwa cells. Our results indicate that, during IFN induction in Namalwa cells by Sendai virus, the IFN genes assume a more open conformation consistent with increased transcriptional activity across these genes.

Internal duplication in human alpha 1 and beta 1 interferons

Metric analysis of the nucleotide sequence of the intron-free human interferon beta 1 (IFN-beta 1) gene by using the Sellers TT algorithm revealed that this gene contains two major repeated segments, which span the entire coding region. These repeats are each approximately 300 nucleotides in length and have 45% identical aligned nucleotides (common bases). When these metrically aligned DNA repeats were translated into amino acids, 9 (19%) of the 47 in-phase amino acid residues were identical (common acids). This internal duplication was also apparent on visual inspection of the amino acid sequence of IFN-beta 1. In addition, metric analysis of the nucleotide sequence of the intron-free IFN-alpha 1 gene showed that this gene also contains two repeats, each approximately 300 nucleotides long, having 47% common bases and 19% common acids. Since the IFN-alpha 1 and -beta 1 genes are known to be related (by the present metric analysis they contain 53% common bases and 45% common acids), a consensus DNA sequence was derived from all four of these repeats. Manual alignment of the separate metric alignments corresponding to the two halves of the IFN-alpha 1 and -beta 1 genes provided a composite alignment with 58% of the alignment positions having the same nucleotide in at least three of the four repeats. When this composite nucleotide alignment was translated to define a composite alignment of the four protein segments, 10 (31%) of the 32 in-phase amino acid residues contained the same amino acid in at least three of the four segments. These sequences relationships provide insight into the origin of the IFN-alpha 1 and -beta 1 genes and furnish an additional basis for comparing them with other related genes.

Interferon-beta-related DNA is dispersed in the human genome

Interferon-beta 1 (IFN-beta 1) complementary DNA was used as a hybridization probe to isolate human genomic DNA clones lambda B3 and lambda B4 from a human genomic DNA library. Blot-hybridization procedures and partial nucleotide sequencing revealed that lambda B3 is related to IFN-beta 1 (and more distantly to IFN-alpha 1). Analyses of DNA obtained from a panel of human-rodent somatic cell hybrids that were probed with DNA derived from lambda B3 showed that lambda B3 is on human chromosome 2. Similar experiments indicated that lambda B4 is not on human chromosomes 2, 5, or 9. The finding that DNA related to the IFN-beta 1 gene (and IFN-alpha 1 gene) is dispersed in the human genome raises new questions about the origins of the interferon genes.