Hormonal and immunological regulation of 2', 5'-oligoadenylate synthetase activity in human peripheral blood mononuclear cells

A newly developed method for assaying 2', 5'-oligoadenylate (2, 5A) synthetase activity by polyacrylamide gel electrophoresis was applied to peripheral blood mononuclear cells (PBMC) from normal subjects, HIV-positive subjects, and renal cell carcinoma (RCC) patients. Sex differences were observed in 2, 5A synthetase activity of PBMC from normal young adults, males having eightfold higher activities of this enzyme than females. Moreover, compared to values for postmenopausal (PM) females receiving estrogen replacement, untreated PM females had higher activities. Collectively, these results suggest that estrogen downregulates 2, 5A synthetase activity. Activities of 2, 5A synthetase were investigated in two disease states associated with altered immune function. In one patient with AIDS-related Kaposi's sarcoma, interferon-alpha (IFN-alpha) therapy increased 2, 5A synthetase activity twofold. In addition, combined therapy with interleukin-2 (IL-2) and IFN-alpha increased 2, 5A synthetase activities in eight of nine patients with RCC. Therefore, in patients receiving immunotherapy with IL-2 and IFN-alpha, our new assay could contribute to evaluation of immune stimulation. In general, studies in vitro confirmed these observations; however, exposure of PBMC from RCC patients revealed that in vitro IL-2 failed to induce this enzyme activity as it did in PBMC from normal volunteers.

Both 17 beta-estradiol and tamoxifen induce c-fos messenger ribonucleic acid expression in human endometrial carcinoma grown in nude mice

We previously demonstrated the estrogen-like effects of tamoxifen on the acceleration of growth and increased progesterone receptor concentrations of human endometrial carcinomas grown in the nude mouse experimental model. In our current study the modulation of protooncogene expression by 17 beta-estradiol and tamoxifen in human endometrial carcinomas was investigated. The protooncogenes investigated in this study were c-fos, c-jun, c-myc, N-myc, HER-2/neu, c-erbB, c-fms, and c-Ha-ras. Among those we found that c-fos expression was induced by 17 beta-estradiol in the following 17 beta-estradiol-sensitive tumors: EnCa-101 and EnCa-X. The induction was apparent within 1 hour, reached peak level at 2 hours (16-fold), and remained constant up to 4 hours. The c-fos messenger ribonucleic acid returned to prestimulation level by 12 hours. Tamoxifen also stimulated c-fos expression, the expression pattern being similar to that of 17 beta-estradiol albeit of a lesser degree. The messenger ribonucleic acid transcripts for other protooncogenes tested did not show significant changes during hormonal manipulation. The induction of c-fos expression by tamoxifen is consistent with its estrogen-like effect on endometrial carcinoma growth.

Mutagenesis of the v-mht/mil oncogene in avian carcinoma virus MH2

Avian carcinoma retrovirus MH2 induces leukemia and solid tumors in chickens and transforms fibroblasts and macrophages in vitro. The genome of MH2 consists of two oncogenes, v-mht/mil and v-myc. Most of the transforming activity of MH2 is attributed to the v-myc oncogene. In contrast, the v-mht/mil oncogene alone does not induce a fully transformed phenotype of avian primary fibroblasts in vitro. It was shown previously that v-mht/mil is the avian homology of the v-raf oncogene in murine sarcoma retrovirus 3611. Because the v-raf oncogene transforms murine fibroblasts very efficiently, the present study tested the hypothesis that an extra segment in the 5' end of v-mht/mil relative to v-raf suppressed the fibroblast-transforming activity of v-mht/mil. By introducing an in-frame deletion of 195 nucleotides into the 5' end of v-mht/mil, the results demonstrate that in the presence of an inactive v-myc oncogene, the 5'-deleted v-mht/mil oncogene fails to transform chicken embryo fibroblasts. Therefore, it is likely that avian primary fibroblasts lack a cellular component that serves as a critical substrate/target for v-mht/mil-induced cellular transformation.

The open reading frame L2 of cottontail rabbit papillomavirus contains antibody-inducing neutralizing epitopes

Polyclonal antisera were generated against bacterially derived fusion proteins of the open reading frames (ORFs) of the capsid proteins of cottontail rabbit papillomavirus (CRPV). The carboxy-terminal two-thirds of CRPV L1 and the carboxy-terminal half of CRPV L2 were cloned into a bacterial expression vector and induced proteins were used as antigen and immunogen. The polyclonal antisera were tested in a series of immunological assays, including ELISA, Western blot, and neutralization of CRPV. ELISA demonstrated that the polyclonal antisera raised against expressed L1 proteins reacted strongly to disrupted CRPV virion antigen and weakly both to intact CRPV virion and disrupted BPV-1 virion. Anti-CRPV L2 antisera reacted strongly only to intact and disrupted CRPV virion antigen. Viral capsid proteins of CRPV were detected in Western blots of HPV-11, BPV-1, and CRPV virus particles by these polyclonal antisera. The anti-L1 sera recognized the major capsid protein (60 kDa) and the anti-L2 sera identified a 76-kDa viral protein of CRPV. Only the antisera generated against expressed L2 neutralized CRPV. The neutralizing titer of the anti-L2 sera, however, was several orders of magnitude lower than the titer of a neutralizing polyclonal antiserum that was generated by immunizations with intact CRPV virions.

Fractionation and characterization of 2',5'-oligoadenylates by polyacrylamide gel electrophoresis: an alternative method for assaying 2',5'-oligoadenylate synthetase

2',5'-Linked oligoadenylates of varying chain lengths (2,5As) are formed from ATP by an interferon (IFN)-induced enzyme, 2',5'-oligoadenylate synthetase (2-5A synthetase). To identify these multiple forms, a method was devised utilizing electrophoretic separation of 32P-labeled 2,5As in a thin 20% polyacrylamide gel containing 7 M urea. A mixture of 2,5As synthesized from rat liver nuclear suspension was fractionated by this method. Each species was eluted from the gel for characterization by specific nucleotidylic enzymes. All major species in the gel were identified, including dimeric, trimeric, and tetrameric forms with either 5' tri- or diphosphates, as well as dephosphorylated species. Thus, in a single step, this method produced a more complete assessment of newly synthesized 2,5As and their degradative products than conventional, multistep DEAE-cellulose chromatography. It also allowed more rapid screening of multiple samples than high-pressure liquid chromatography (HPLC). This method, used to assay 2-5A synthetase induction by IFN-alpha in human T-cell H9 and CEM-CM3 lines, should be applicable for routine analysis of clinical specimens.

Molecular cloning of the ets proto-oncogene of the sea urchin and analysis of its developmental expression

The locus SU(Lv)-ets-2 of the sea urchin Lytechinas variegatus related to the oncogene v-ets of avian erythroblastosis virus E26 has been molecularly cloned. The cloned DNA was found to contain a region with a high degree of homology to E26 v-ets. The sea urchin homology with v-ets starts at a consensus splice acceptor sequence and stops at the point where homology between v-ets and human c-ets ends. This region corresponds to the Hu-ets-2 homologous sequences defined by Watson et al. (1985, Proc. Natl. Acad. Sci, USA 82, 7294-7298). Ninety-one out of 97 (or 94%) predicted amino acids are identical between sea urchin c-ets and E26 v-ets over the region of homology. This degree of homology exceeds the maximum homology previously found between any oncogene and an invertebrate homolog. A somewhat weaker homology with the Hu-ets-2 sequences continues beyond, for 13 codons, ending at a common termination codon. Northern blot analysis of mature unfertilized eggs and early embryos from sea urchins of the species Strongylocentrotus purpuratus revealed a single 6.8-kb ets-related RNA that is expressed at a maximum level during the early stages of embryonic development. This RNA species is polyadenylated indicating that it is the message for the sea urchin ets-2 gene.

Spectrum of natural antibodies against five HTLV-III antigens in infected individuals: correlation of antibody prevalence with clinical status

The genome of the HTLV-III/LAV retrovirus, the etiologic agent of the acquired immunodeficiency syndrome (AIDS), encodes the viral structural proteins (envelope and core proteins), the reverse transcriptase, a transactivation protein (tat-III), as well as two other proteins (3'orf, sor) of unknown function. We studied the prevalence of natural antibodies against envelope, gag, 3'orf, sor, and tat-III in the sera of HTLV-III infected individuals in an attempt to correlate clinical status with seropositivity to specific HTLV-III antigens. We selected 101 sera; 16 were obtained from normal donors with no known risk factors, and 85 were from patients with full-fledged AIDS (28 cases), AIDS-related complex (ARC, 22 cases), and healthy people at risk (homosexuals, intravenous [IV] drug users, relatives of AIDS patients; 35 cases). Seropositivity for antibodies against the envelope (gp41) and gag antigens (p15, p24) was determined by Western blot using disrupted HTLV-III virions. Of the 101 sera, all 16 from nonrisk donors and 3/35 from healthy at-risk donors were negative for antibodies against either the gp41 or p15 and p24. The remaining 82 sera were seropositive for either the gp41 and/or the p15 and p24. All sera were then tested against the three known HTLV-III antigens (3'orf, sor, and tat-III) that have been synthesized in bacteria. Our data indicate that all the HTLV-III antigens tested are immunogenic in vivo. No significant difference in antibody prevalence to gp41 (close to 100%) and to the 3'orf, sor, and tat-III proteins (approximately 50%) was observed with regard to stage of the disease. In contrast, the prevalence of antibodies against the core antigens decreased from approximately 100% in infected people with no clinical signs of disease to 50% in ARC and AIDS patients. The percentage of patients seropositive for all five antigens tested was increased in the AIDS group. These results indicate that the greatest antibody prevalence was obtained using viral envelope antigen and further suggest that screening with the newly identified 3'orf, sor, and tat-III proteins as antigens would confer no further diagnostic advantage. The pattern of natural antibodies observed during disease progression did not suggest any pathogenetic mechanism.

Identification of HTLV-III/LAV sor gene product and detection of antibodies in human sera

The nucleotide sequence of the genome of HTLV-III, the infectious agent etiologically associated with the acquired immune deficiency syndrome, predicts a small open reading frame, termed sor, located between the pol and env genes. A DNA segment containing 82 percent of the sor region was inserted into a prokaryotic expression vector, pJL6, to determine whether sor encodes a viral protein and to gain some insight into its possible function. The bacterially synthesized sor protein reacted with sera from individuals infected with HTLV-III, indicating that sor is expressed as a protein product or products that are immunogenic in vivo. Antibodies to the purified, bacterially synthesized sor protein were found to react specifically with the same protein and also with a protein of molecular weight 23,000 (23K) in HTLV-III-infected H9 cell extracts. The 23K protein comigrated with a protein immunoprecipitated by the serum of a hemophiliac patient with antibodies to HTLV-III, suggesting that this protein is probably the sor gene product.

Sites of recombination between the transforming gene of avian myeloblastosis virus and its helper virus

The sites of recombination between the transforming gene of avian myeloblastosis virus (AMV) and its natural helper myeloblastosis-associated virus (MAV) have been determined. In AMV, the cellular sequence substituting for the viral envelope (env) gene gives rise to a different carboxyl terminus of the DNA polymerase. The 5'-recombination site coincides with the RNA splice acceptor site for the production of env mRNA in MAV-infected cells. The 3'-recombination site reveals that the last 11 amino acids including the termination codon are shared by the env protein and AMV transforming protein. The RNA splice acceptor site for the generation of subgenomic v-myb mRNA is located 84 nucleotides downstream from the 5'-recombination site. The AMV transforming protein consists of helper virus-related sequences at both of its amino and carboxyl termini, and all but 84 nucleotides of the cell-derived v-myb sequence. The comparison of MAV gp85 amino acid sequence with those of subgroups B, C, and E indicates that the MAV present in clone lambda 10A2-1 belongs to subgroup B. The high degree of homology among different avian retroviruses of the same subgroup indicates that the amino acid sequence of gp85 is important in determining the conformation of the envelope glycoprotein.

Production of oncogene-specific proteins and human T-cell leukemia (lymphotropic) retrovirus (HTLV-I) envelope protein in bacteria and its potential for use in human cancers and seroepidemiological surveys

The oncogenes coding for the Harvey murine sarcoma virus p21ras protein as well as those coding for myc, myb, and mht products were fused to the amino-terminal portion of the bacteriophage lambda cII gene on the expression vector pJL6. In addition two regions of the gene for the human T-cell leukemia virus subgroup I (HTLV-I) envelope were expressed in our bacterial system. Each of 11 human sera tested that had been shown to contain antibodies to HTLV-I or -II by an enzyme-linked immunosorbent assay recognized the bacterially synthesized envelope proteins. No reaction was detected when 17 control sera were tested. This system will be useful for large-scale seroepidemiological surveys for HTLV-I and related human retroviruses. The other oncogene products expressed in our bacterial vector system also demonstrated specific immunoreactivities. In addition to this feature the bacterial ras protein was seen to bind guanosine diphosphate and was capable of autophosphorylation. Taken together these data suggest that the proteins produced with high efficiency by the bacterial expression system can be immunologically recognized as antigens and can in part perform some of their associated biochemical functions.

Analysis of the cellular proto-oncogene mht/raf: relationship to the 5' sequences of v-mht in avian carcinoma virus MH2 and v-raf in murine sarcoma virus 3611

The avian carcinoma virus MH2 contains a hybrid gene delta gag-mht with a contiguous open reading frame of 2682 base pairs as well as v-myc and avian helper virus-related sequences. delta gag is a partial retroviral core protein gene while v-mht and v-myc are cell-drived sequences. The v-mht sequence can be divided into two regions: the v-raf-related region at its 3' end contains 969 nucleotides which are 94% related as amino acid sequence to the onc-specific v-raf sequence of murine sarcoma virus 3611 (MSV 3611), and the v-mht-specific region at its 5' end contains 173 nucleotides which are unrelated to either MSV 3611 or avian helper virus sequences. To study the origin of the v-mht-specific sequences, the 5' region of the proto-mht/raf gene was molecularly cloned from a phage lambda library containing genomic chicken sequences. Nucleic acid hybridization, heteroduplex and DNA sequence analyses indicate that the v-mht-specific sequences are encoded in three exons. The first and second exons are separated by a 3.4-kb intron while the second and third exons are separated by a 90-bp intron. The last 14 bp of the third exon are shared with v-raf and thus represent the start of v-raf-related sequences. The junction between v-mht-unrelated and related cellular sequences occurs within the first exon. There is no homology between the v-mht-unrelated sequences and the retroviral helper sequences indicating that the viral transduction of the proto-mht/raf sequences occurred through illegitimate recombination. The predominant v-mht-related messenger RNA (4.0 kb) hybridizes to several noncontiguous regions on the molecularly cloned cellular proto-mht/raf DNA indicating that the proto-mht/raf gene is distributed over at least 10 kb of DNA in the chicken genome. Thus the v-mht oncogene is a subset of its normal cellular homolog in that it lacks intervening sequences and possibly lacks 5'-coding sequences.

Two oncogenes in avian carcinoma virus MH2: myc and mht

The 5.2-kilobase (kb) RNA genome of avian carcinoma virus MH2 has the genetic structure 5' - delta gag (0.2 kb)-mht (1.2 kb)-myc (1.4 kb)-c(0.4 kb)-poly (A) (0.2 kb)-3'. delta gag is a partial retroviral core protein, mht and myc are cell-derived MH2-specific sequences, and c is the 3'-terminal retroviral vector sequence. the following results were obtained from the complete nucleotide sequences of the mht and myc genes in MH2. (i) delta gag-mht forms a hybrid gene with a contiguous reading frame of 2682 nucleotides that terminates with a stop codon near the 3' end of the mht gene. The 3' 969 nucleotides of mht up to the stop codon are 80% sequence related to the onc-specific raf sequence of murine sarcoma virus 3611 (MSV 3611) (94% homologous at the deduced amino acid level). (ii) The myc coding region in MH2 is preceded by 181 nucleotides derived from the intron immediately upstream from the second exon of the chicken cellular proto-myc gene, followed by an RNA splice acceptor site shared with the proto-myc gene, followed by an RNA splice acceptor site shared with the proto-myc, beyond which it is colinear up to a 3'-termination codon and 40 noncoding nucleotides with the myc sequences of avian retrovirus MC29 and chicken proto-myc. Thus, myc forms, together with a 5' retroviral exon, a second MH2-specific gene. It is concluded that MH2 contains two genes with oncogenic potential, the delta gag-mht gene, which is closely related to the delta gag-raf transforming gene of MSV 3611, and the myc gene, which is related to the transforming gene of MC29. Furthermore, it may be concluded that the cellular proto-onc genes, which on sequence transduction become viral onc genes, are a small group because among the 19 known onc sequences, 5 are shared by different taxonomic groups of viruses of which the mht/raf homology is the closest so far.

Nucleotide sequence of avian carcinoma virus MH2: two potential onc genes, one related to avian virus MC29 and the other related to murine sarcoma virus 3611

The 5.2-kilobase (kb) RNA genome of avian carcinoma virus MH2 has the genetic structure 5'-delta gag (0.2 kb)- mht (1.2 kb)-myc (1.4 kb)-c (0.4 kb)-poly(A) (0.2 kb)-3'. delta gag is a partial retroviral core protein gene, mht and myc are cell-derived MH2-specific sequences, and c is the 3'-terminal retroviral vector sequence. Here we have determined the nucleotide sequence of 3.5 kb from the 3' end of delta gag to the 3' end of molecularly cloned proviral MH2 DNA, in order to elucidate the genetic structure of the virus and to compare it with other mht - and myc-containing oncogenic viruses as well as with the chicken proto-myc gene. The following results were obtained: (i) delta gag- mht forms a hybrid gene with a contiguous reading frame of 2682 nucleotides that terminates with a stop codon near the 3' end of mht . The 3' 969 nucleotides of mht up to the stop codon are 80% sequence related to the onc-specific raf sequence of murine sarcoma virus 3611 (94% homologous at the deduced amino acid level). (ii) The myc sequence is preceded by an RNA splice acceptor site shared with the cellular proto-myc gene, beyond which it is colinear up to a 3'-termination codon and 40 noncoding nucleotides with the myc sequences of avian retrovirus MC29 and chicken proto-myc. Thus, myc forms, together with a 5' retroviral exon, a second MH2-specific gene. (iii) myc is followed by the 3'-terminal c region of about 400 nucleotides, which is colinear with that of Rous sarcoma virus except for a substitution near the 5' end of the long terminal repeat. It is concluded that MH2 contains two genes with oncogenic potential, the delta gag- mht gene, which is closely related to the delta gag-raf transforming gene of MSV 3611, and the myc gene, which is related to the transforming gene of MC29. Furthermore, it may be concluded that the cellular proto-onc genes, which on sequence transduction become viral onc genes, are a small group because among the 19 known onc sequences, 5 are shared by different taxonomic groups of viruses of which the mht /raf homology is the closest determined so far.

A common onc gene sequence transduced by avian carcinoma virus MH2 and by murine sarcoma virus 3611

A common cellular sequence was independently transduced by avian carcinoma virus MH2 (v-mht) and murine sarcoma virus (MSV) 3611 (v-raf). Comparison of the nucleotide sequences of v-mht and v-raf revealed a region of homology that extends over 969 nucleotides. The homology between the corresponding amino acids was about 95 percent with only 19 of 323 amino acids being different. With this example, 5 of the 19 known different viral onc genes have been observed in viruses of different taxonomic groups. These data indicate that (i) the number of cellular proto-onc genes is limited because, like other viruses of different taxonomic groups, MH2 and MSV 3611 have transduced the same onc gene-specific sequences from different cell species and (ii) that specific deletion and linkage of the same proto-onc sequences to different viral vector elements affect the oncogenic potential of the resulting viruses. The difference in transformation capabilities of MH2 and MSV 3611 serves as an example.

Avian carcinoma virus MH2 contains a transformation-specific sequence, mht, and shares the myc sequence with MC29, CMII, and OK10 viruses

Avian carcinoma virus MH2 has been grouped together with MC29, CMII, and OK10, because all of these viruses share a transformation-specific sequence termed myc. A 5.2-kilobase (kb) DNA provirus of MH2 has been molecularly cloned. The complete genetic structure of MH2 is 5'-delta gag(1.9-kb)-mht(1.2-kb)-myc(1.3-kb)-delta env(?) and noncoding c-region (0.2-kb)-3'. delta gag, delta env, and c are genetic elements shared with nondefective retroviruses, whereas mht is a unique, possibly MH2 transformation-specific, sequence. Hybridizations with normal chicken DNA and cloned chicken c-myc DNA indicate that the mht sequence probably derives from a normal cellular gene that is distinct from the c-myc gene. The genetic structure of MH2 suggests that the delta gag and mht sequences function as a hybrid gene that encodes the p100 putative transforming protein. The myc sequence of MH2 appears to encode a second transforming function. Therefore, it seems that MH2 contains two genes with possible oncogenic function, whereas MC29, CMII, and OK10 each carries a single hybrid delta gag-myc transforming gene. It is remarkable that, despite these fundamental differences in their primary structures and mechanisms of gene expression, MH2 and MC29 have very similar oncogenic properties.

The intervening sequence of the ribosomal RNA gene is highly conserved between two Tetrahymena species

The entire intervening sequence of Tetrahymena thermophila ribosomal DNA has been determined. It is 413 nucleotides long and has the same splice junctions as those in T. pigmentosa. There is 93% homology between the intervening sequences in the two species, and 100% homology between their adjacent 26S RNA coding regions.

Base distribution in the coding and noncoding regions in the rDNA of Lytechinus variegatus

The EcoRI restriction endonuclease cleaves rDNA repeat units of the sea urchin Lytechinus variegatus into four fragments. The G + C contents of all four cloned restriction fragments were determined by ispycnic analysis. Electron microscopic denaturation mapping of one of the fragments allowed alignment of the denaturation pattern with the restriction map and correlation with previously reported transcriptional data. From these results the base distribution in the spacer region and regions coding for rRNAs was derived.

Recognition site of Escherichia coli B restriction enzyme on phi XsB1 and simian virus 40 DNAs: an interrupted sequence

Methyl groups placed on varphiXsB1 replicative form DNA by the Escherichia coli B modification enzyme are located in the overlap between fragments Mbo II-3 and Alu I-2, a 61-base-pair DNA segment. Mutations that led to loss of susceptibility to restriction by E. coli B occurred within this segment at three positions spanning 14 nucleotides. A sequence difference between varphiXsB1 and varphiXam3cs70, a varphiX174 strain not restricted by E. coli B, occurs at one of these positions. The site on simian virus 40 DNA methylated by the modification enzyme is located in the 115-base-pair overlap between fragments Hae III-I and Alu I-G. The sequences of these segments of varphiXsB1 and simian virus 40 DNA and two regions of phage f1 DNA recognized by the E. coli B restriction enzyme [Ravetch, J. V., Horiuchi, K. & Zinder, N. D. (1978) Proc. Natl. Acad. Sci. USA 75, 2266-2270] contain a homology of nine bases in the configuration:5'-T-G-A... 8N... T-G-C-T... 9N... T-N-N-T-3'. The sequence 5'-T-G-A... 8N... T-G-C-T-3' may constitute the restriction enzyme recognition site since it does not occur in varphiXam3cs70 DNA and occurs only once in simian virus 40 DNA, and since all observed mutations leading to loss of the site occur at one of the bases specified by this sequence. Analysis of the sequence of varphiXam3cs70 showed that if no other residues are recognized, all seven of these bases are essential for recognition and the interval between the two groups of specified bases must be precisely eight.