Retrovirus sequences in a leukemic gibbon and its contact: evidence for partial provirus in the nonleukemic gibbon

Mice transgenic for a human porcine endogenous retrovirus receptor are susceptible to productive viral infection

Porcine endogenous retrovirus (PERV) is considered one of the major risks in xenotransplantation. No valid animal model has been established to evaluate the risks associated with PERV transmission to human patients by pig tissue xenotransplantation or to study the potential pathogenesis associated with PERV infection. In previous work we isolated two genes encoding functional human PERV receptors and proved that introduction of these into mouse fibroblasts allowed the normally nonpermissive mouse cells to become productively infected (T. A. Ericsson, Y. Takeuchi, C. Templin, G. Quinn, S. F. Farhadian, J. C. Wood, B. A. Oldmixon, K. M. Suling, J. K. Ishii, Y. Kitagawa, T. Miyazawa, D. R. Salomon, R. A. Weiss, and C. Patience, Proc. Natl. Acad. Sci. USA 100:6759-6764, 2003). In the present study we created mice transgenic for human PERV-A receptor 2 (HuPAR-2). After inoculation of transgenic animals with infectious PERV supernatants, viral DNA and RNA were detected at multiple time points, indicating productive replication. This establishes the role of HuPAR-2 in PERV infection in vivo; in addition, these transgenic mice represent a new model for determining the risk of PERV transmission and potential pathogenesis. These mice also create a unique opportunity to study the immune response to PERV infection and test potential therapeutic or preventative modalities.

Identification of receptors for pig endogenous retrovirus

Xenotransplantation of porcine tissues has the potential to treat a wide variety of major health problems including organ failure and diabetes. Balanced against the potential benefits of xenotransplantation, however, is the risk of human infection with a porcine microorganism. In particular, the transmission of porcine endogenous retrovirus (PERV) is a major concern [Chapman, L. E. & Bloom, E. T. (2001) J. Am. Med. Assoc. 285, 2304-2306]. Here we report the identification of two, sequence-related, human proteins that act as receptors for PERV-A, encoded by genes located on chromosomes 8 and 17. We also describe homologs from baboon and porcine cells that also are active as receptors. Conversely, activity could not be demonstrated with a syntenic murine receptor homolog. Sequence analysis indicates that PERV-A receptors [human PERV-A receptor (HuPAR)-1, HuPAR-2, baboon PERV-A receptor 2, and porcine PERV-A receptor] are multiple membrane-spanning proteins similar to receptors for other gammaretroviruses. Expression is widespread in human tissues including peripheral blood mononuclear cells, but their biological functions are unknown. The identification of the PERV-A receptors opens avenues of research necessary for a more complete assessment of the retroviral risks of pig to human xenotransplantation.

Philadelphia chromosome-negative chronic myelogenous leukemia with rearrangement of the breakpoint cluster region. Long-term follow-up results

BACKGROUND

Five to 10% of patients with chronic myelogenous leukemia (CML) do not have the Philadelphia chromosome (Ph), but one-third of them have rearrangements of the breakpoint cluster region (BCR-positive).

METHODS

The authors analyzed the characteristics, treatment response, and prognosis of 23 patients with BCR-positive, Ph-negative CML, and compared them with patients with Ph-positive CML, Ph-negative BCR-negative CML and chronic myelomonocytic leukemia (CMML) treated during the same period.

RESULTS

Seventeen patients had early chronic phase CML, 3 had late chronic phase, 2 had accelerated phase, and 1 had blastic phase. The median age was 44 years (range, 14-71 years), median platelet count was 402 x 10(9)/l, and median leukocyte count was 86 x 10(9)/l. Fourteen of the 17 patients with early chronic phase CML received alpha-interferon; 12 (86%) achieved complete hematologic remission. Median survival in chronic phase CML was 60 months (range, 3-90+ months). Patients with Ph-negative BCR-positive CML and those with Ph-positive CML had similar characteristics and outcome. Compared with patients with Ph-negative BCR-negative CML and CMML, patients with Ph-negative BCR-positive CML and Ph-positive CML were significantly younger, had a significantly higher incidence of leukocytosis, thrombocytosis, and peripheral and marrow basophilia, and a significantly lower incidence of anemia, thrombocytopenia, marrow blast percent, and peripheral and marrow monocytosis. The median survival was 60 months for Ph-negative BCR-positive CML, 73 months for Ph-positive CML, 25 months for Ph-negative BCR-negative CML, and 9 months for CMML (P < 0.001). When analyzed adjusting for their stage, patients classified with Ph-negative BCR-positive CML. Stage I disease had a significantly better survival than did patients with Ph-negative BCR-negative CML (P < 0.02).

CONCLUSIONS

Patients with Ph-negative BCR-positive CML are similar to those with Ph-positive CML and should be treated with the same approaches.

Abnormalities in the PRAD1 (CYCLIN D1/BCL-1) oncogene are frequent in cervical and vulvar squamous cell carcinoma cell lines

BACKGROUND

CYCLIN D1, a cell-cycle control gene, recently has been shown to be identical to an oncogene alternatively known as BCL-1 and PRAD1 and implicated in centrocytic lymphomas and parathyroid adenomas, respectively. PRAD1 complexes to the product of the retinoblastoma (Rb) tumor suppressor gene, an event followed by Rb inactivation. Squamous cell carcinomas of the cervix and vulva are gynecologic tumors in which human papillomaviruses have been implicated as an initiating event, and proteins derived from these viruses also complex with an inactivate Rb. Because of the overlap in some of the molecular processes mediated by human papillomaviruses and by the PRAD1 oncogene, the authors analyzed the PRAD1 (CYCLIN D1/BCL-1) genomic structure and expression in vulvar and cervical squamous cell carcinoma cell lines.

METHODS

PRAD1 DNA and PRAD1 mRNA expression were assessed by Southern and Northern blotting, respectively, in 13 squamous cell carcinoma cell lines of gynecologic origin (10, cervical cancer; 3, vulvar cancer).

RESULTS

We found low baseline levels of a 4.5-kb PRAD1 transcript in a series of control cell lines, which were derived from normal fibroblasts, various hematologic malignancies, and a choriocarcinoma. PRAD1 mRNA overexpression (> or = 10-fold greater than that in control lines) was seen in all three vulvar carcinoma cell lines, two of which also showed amplification (5-fold and > 10-fold) of PRAD1 genomic sequences. Abnormalities of PRAD1 also were seen in 4 of the 10 cervical cancer cell lines and included overexpression of PRAD1 transcripts (3-9-fold) in 3 lines and rearrangement of PRAD1 DNA in an additional line that, however, did not shown any aberration in PRAD1 mRNA as discernible by Northern blotting. PRAD1 abnormalities were observed in three of the four cervical cell lines derived from metastatic sites and in one of the six cervical lines derived from primary tissue.

CONCLUSIONS

Seven of 13 squamous cell lines of gynecologic origin showed abnormalities of PRAD1. These abnormalities included amplification and rearrangement of DNA and overexpression of mRNA. The role of PRAD1 as a cell-cycle regulatory gene and its interactions with the Rb tumor suppressor gene suggests that PRAD1 deregulation may be a significant molecular event in the evolution of these tumors.

Subcellular localization of Bcr, Abl, and Bcr-Abl proteins in normal and leukemic cells and correlation of expression with myeloid differentiation

We used specific antisera and immunohistochemical methods to investigate the subcellular localization and expression of Bcr, Abl, and Bcr-Abl proteins in leukemic cell lines and in fresh human leukemic and normal samples at various stages of myeloid differentiation. Earlier studies of the subcellular localization of transfected murine type IV c-Abl protein in fibroblasts have shown that this molecule resides largely in the nucleus, whereas transforming deletion variants are localized exclusively in the cytoplasm. Here, we demonstrate that the murine type IV c-Abl protein is also found in the nucleus when overexpressed in a mouse hematopoietic cell line. However, in both normal and leukemic human hematopoietic cells, c-Abl is discerned predominantly in the cytoplasm, with nuclear staining present, albeit at a lower level. In contrast, normal endogenous Bcr protein, as well as the aberrant p210BCR-ABL and p190BCR-ABL proteins consistently localize to the cytoplasm in both cell lines and fresh cells. The results with p210BCR-ABL were confirmed in a unique Ph1-positive chronic myelogenous leukemia (CML) cell line, KBM5, which lacks the normal chromosome 9 and hence the normal c-Abl product. Because the p210BCR-ABL protein appears cytoplasmic in both chronic phase and blast crisis CML cells, as does the p190BCR-ABL in Ph1-positive acute leukemia, a change in subcellular location of Bcr-Abl proteins between cytoplasm and nucleus cannot explain the different spectrum of leukemias associated with p210 and p190, nor the transition from the chronic to the acute leukemia phenotype seen in CML. Further analysis of fresh CML and normal hematopoietic bone marrow cells reveals that p210BCR-ABL, as well as the normal Bcr and Abl proteins, are expressed primarily in the early stages of myeloid maturation, and that levels of expression are reduced significantly as the cells mature to polymorphonuclear leukocytes. Similarly, a decrease in Bcr and Abl levels occurs in HL-60 cells induced by DMSO to undergo granulocytic differentiation. The action of p210BCR-ABL and its normal counterparts may, therefore, take place during the earlier stages of myeloid development.

Characterization of the DiFi rectal carcinoma cell line derived from a familial adenomatous polyposis patient

The DiFi human colorectal cancer cell line was recently established from a familial adenomatous polyposis patient with extracolonic features characteristic of the Gardner syndrome. These cells have now been propagated for 150 passages in standard culture media and vessels without feeder layers or collagen coatings. They retain features of colonic epithelial cells such as surface microvilli, secretory vesicles, and desmosomes. Cytosol of DiFi cells contains a high level (502 U/mg protein) of the mucin CA 19-9. In addition, DiFi cells produce carcinoembryonic antigen, and induce tumors in athymic mice. Cytoskeleton analysis of DiFi cells by fluorescence microscopy showed a pronounced disorganization of actin cable structure. The isozyme genetic signature of DiFi cells is unique (0.01 probability of finding the same genetic signature in a different cell line), differs from that of HeLa cells, and has expressional features seen in other colorectal cell lines. The DiFi cell karyotype is tetraploid, contains many marker chromosomes, and shows numerous episomal particles. Two copies of chromosome 18 were absent, and only a single normal chromosome 17 was found. This parallels detection of allelic losses from DiFi cell DNA at loci on chromosomes 17p and 18 using molecular (cDNA) probes. DiFi cells clearly express transcripts for the c-myc proto-oncogene, the c-myb proto-oncogene, and the p53 tumor suppressor gene. Transforming growth factor beta inhibits DiFi cell growth in soft agar and suppresses c-myc expression in these cells. The value of this cell line in the study of genetic alterations in colorectal cancer is discussed.

Infant leukemia: an analysis of nine Chinese patients

A study was made of the cellular and molecular characteristics of nine Chinese infants, consecutively presenting with acute leukemia. Five cases were acute lymphoblastic leukemia (ALL); four were acute nonlymphoblastic leukemia (ANLL). Hyperleukocytosis, hepatosplenomegaly, and poor response to conventional therapy were common features, and CNS involvement was detected at diagnosis in three cases. The blast cells from all five cases with ALL expressed early B-cell markers, i.e., HLA-DR+, CD19+, but CD10-. Terminal deoxynucleotidyl transferase (TdT) was present in blasts from four of the five cases and periodic acid-Schiff staining in blasts from two patients only. The leukemic cells of one patient also showed positive nonspecific esterase activity and expressed myeloid-associated antigens CD33 (My9), CD11 (OkM1), and CD14 (My4 and Mo2). Molecular analysis of leukemic cell DNA from this and two other patients showed rearrangement of the immunoglobulin (Ig) heavy-chain genes, but without any evidence of kappa light-chain gene rearrangement. T-cell receptor (TCR) genes remained in the germline configuration in these cases. Cytogenetic analysis showed translocation t(4;11) (q21;q23) in all four cases studied. In the group of ANLL, three cases belonged to the M4 and one to the M2 subtype. Chromosomal abnormality involving 11q23 was also detected in two patients: t(11;17)(q23;q11) and del(11)(q14q23) in each case respectively. Neither Ig nor TCR gene rearrangement was present in blast cells from patients with ANLL. The data indicate that chromosomal rearrangement of band 11q23 was quite common in Chinese infants with either form of leukemia, a finding that may have pathogenetic implications.

Vaccination trials in rhesus monkeys with a minor, invariant, Plasmodium knowlesi 66 kD merozoite antigen

A minor Plasmodium knowlesi 66 kD antigen, which plays an essential role in merozoite invasion, has been shown to be stable in distinct variants and strains of the parasite, and in the face of a specific immune response from the host. Parasites were unable to produce novel molecule(s) to replace it functionally, even in the presence of specific immune pressure. Rhesus monkeys immunized with the purified 66 kD antigen, with saponin as adjuvant, produced antibody which inhibited merozoite invasion of red cells in vitro. Four out of six immunized rhesus monkeys demonstrated clinically effective immunity when challenged at a time of known or presumed high inhibitory antibody titre. When immunization failed to protect, it was ascribed to insufficient levels of specific antibody attributable either to a suboptimal dose of antigen or the use of an inadequate adjuvant.

Association of the Epstein-Barr virus with lymphoepithelioma of the thymus

A 30-year-old woman with the histologic diagnosis of lymphoepithelioma of the thymus is reported on. Investigation of Epstein-Barr serology showed evidence of infection, and Southern blot analysis showed the presence of the viral genome in the tumor specimen. The patient achieved complete remission after treatment with combination chemotherapy, autologous bone marrow transplant, and radiotherapy. These findings suggest that lymphoepithelioma of the thymus may have a viral pathogenesis similar to that of nasopharyngeal carcinoma.

Molecular analysis of chromosome 22 breakpoints in adult Philadelphia-positive acute lymphoblastic leukaemia

The Philadelphia (Ph) translocation, t(9:22)(q 34:q11), is found in the majority of patients with chronic myelogenous leukaemia (CML) as well as in approximately 20% of adult acute lymphoblastic leukaemia (ALL) patients. The chromosome 22 breakpoint in CML has been localized within a restricted 5.8 kb segment of DNA known as the breakpoint cluster region (bcr). To investigate the chromosome 22 breakpoint in ALL, we analysed five adult Ph-positive ALL patients for bcr rearrangement. Rearrangement was detected within bcr in two patients. However, in one patient the break occurred 5' to the first exon of bcr and in two patients the bcr region was not involved. We conclude that the identical cytogenetic marker, t(9:22), may yield a different genomic configuration in ALL and CML.

Ha-ras-1 restriction fragment length polymorphism and susceptibility to colon adenocarcinoma

It is not yet clear whether some polymorphic variants of the Ha-ras-1 gene confer genetic predisposition to cancer. However, recent data on myelodysplasia and lung cancer are controversial. To clarify this point, 62 colorectal adenocarcinoma patients were examined for the Ha-ras-1 gene restriction fragment length polymorphism and results were compared with those of 108 healthy blood donors. No Ha-ras-1 polymorphic variants specifically associated with the cancer patients were detected. However, a specific genotype was significantly more frequent in the healthy donors than in the cancer patients (16% versus 5%), suggesting an interaction between the two alleles of the gene.

A novel c-abl protein product in Philadelphia-positive acute lymphoblastic leukaemia

Activation of cellular proto-oncogenes as a result of chromosomal abnormalities has been implicated in the development of some human malignancies. Perhaps one of the most striking examples of this association occurs in chronic myelogenous leukaemia, where the Philadelphia (Ph) translocation results in substitution of the 5' end of the c-abl proto-oncogene with bcr gene sequences. A unique hybrid bcr-abl message is produced. As the Ph translocation is also present in some patients with acute lymphoblastic leukaemia, we initiated studies to determine if similar genomic events occur in these two different forms of Ph-positive leukaemia. Here we report that the Ph translocation in acute lymphoblastic leukaemia can result in production of a novel aberrant c-abl protein that is distinct from the bcr-abl protein found in Ph-positive chronic myelogenous leukaemia. Our observations suggest that alternative mechanisms of activation of c-abl exist, and may be important in the development of human acute lymphoid rather than chronic myeloid malignancies.

SIg-E- ("null-cell") non-Hodgkin's lymphomas. Multiparametric determination of their B- or T-cell lineage

The authors performed immunophenotypic, functional, and molecular analysis of the neoplastic cells from 20 cases of SIg-, E-("null-cell") non-Hodgkin's lymphoma (NHL) in order to determine their lineage, better define this category of NHL, and evaluate the lineage specificity of selected phenotypic markers and the individual and collective utility of these approaches. They assigned 4 cases to the T-cell lineage, and 15 cases to the B-cell lineage, and 1 case remained indeterminant on the basis of immunophenotypic analysis. The cells from 2 cases assigned to the T-cell lineage expressed unusual phenotypes, but their T-cell derivation was confirmed by the demonstration of helper function in vitro. The 15 cases assigned to the B-cell lineage expressed a variety of B-cell-associated antigens, consistent with various stages of B-cell differentiation. Monoclonal antibodies OKT3, OKT4, OKT6, and OKT8 exhibited T-cell lineage restriction; and monoclonal antibodies OKB2, BL1, and B1 exhibited B-cell lineage restriction. Ia, TdT, cALLa, OKT9, and OKT10 exhibited lineage infidelity. Southern blot analysis for immunoglobulin heavy chain gene rearrangements confirmed 18 of the 19 lineage assignments made by immunophenotypic analysis and suggested that the 1 case of indeterminate phenotype was a B-cell neoplasm. One T-cell (OKT3+, T4+) neoplasm exhibited rearranged immunoglobulin heavy chain genes. Thus, neither immunophenotypic analysis nor the demonstration of rearranged immunoglobulin heavy chain genes alone permitted the satisfactory lineage assignment of every case of SIg-, E- NHL. However, combined immunophenotypic, functional, and genotypic analysis allowed us to assign every SIg-, E-NHL to the B- or T-cell lineage and to demonstrate that truly "null-cell" NHLs are probably very uncommon.

Human T-cell leukemia-lymphoma virus (HTLV): cloning of an integrated defective provirus and flanking cellular sequences

Human T-cell leukemia-lymphoma virus (HTLV) is the first unequivocal human retrovirus. Seroepidemiological and virus isolation studies indicate that HTLV is etiologically associated with a subtype of adult T-cell malignancy. We have molecularly cloned approximately 1 kilobase of sequences derived from the 5' and 3' termini of the HTLV genome. Use of these clones as probes allowed isolation of a 9.8-kilobase EcoRI fragment from a genomic DNA library of an HTLV-infected neoplastic T-cell line (CR). Analysis of this clone revealed the presence of cellular sequences flanking approximately 5 kilobases of viral sequences including one long terminal repeat sequence. The 5' and 3' clones, as well as subclones derived from different regions of the genomic clone, were used as probes to compare integrated proviruses and viral RNA expression in different HLTV-infected neoplastic T cell lines. The results indicate that the infected cells are of clonal origin with respect to the virus integration sites and they express multiple viral mRNA species including a 35S RNA.

Abundant transcription of a cellular gene in T cells infected with human T-cell leukemia-lymphoma virus

Human T-cell leukemia-lymphoma virus (HTLV) is a type C retrovirus associated with a subtype of mature T-cell malignancy in humans. HTLV also infects normal human cord blood mature T lymphocytes in vitro and induces a number of phenotypic changes in these cells, including their continuous growth and partial or complete independence of T-cell growth factor (TCGF). As part of our initial study designed to analyze gene(s) specifically activated by HTLV infection, we have isolated a recombinant DNA clone by differential screening of a cDNA library made from mRNA of a human T-cell lymphoma cell line producing HTLV. This cDNA identifies a single-copy gene in all human DNAs and a single mRNA species of 2.3 kilobases expressed at several hundred copies per cell in five HTLV-positive neoplastic T-cell lines. In addition, cord blood T lymphocytes infected with HTLV, but not the uninfected counterparts, express high levels of mRNA from this gene. A survey of different human hematopoietic cell types showed that this gene is expressed at low or undetectable levels (less than 10 copies) in human T, B, myeloid, or erythroid cell lines; in moderate amounts in lymphoid precursor (immature) cell lines; and in high amounts in lectin-activated mature T-cells, comparable to those of HTLV-infected T-cell lines. The precise function of this gene has not yet been determined.

Human c-myc onc gene is located on the region of chromosome 8 that is translocated in Burkitt lymphoma cells

Human sequences related to the transforming gene (v-myc) of avian myelocytomatosis virus (MC29) are represented by at least one gene and several related sequences that may represent pseudogenes. By using a DNA probe that is specific for the complete gene (c-myc), different somatic cell hybrids possessing varying numbers of human chromosomes were analyzed by the Southern blotting technique. The results indicate that the human c-myc gene is located on chromosome 8. The analysis of hybrids between rodent cells and human Burkitt lymphoma cells, which carry a reciprocal translocation between chromosomes 8 and 14, allowed the mapping of the human c-myc gene on region (q24 leads to qter) of chromosome 8. This chromosomal region is translocated to either human chromosome 2, 14, or 22 in Burkitt lymphoma cells.

Cloning and characterization of different human sequences related to the onc gene (v-myc) of avian myelocytomatosis virus (MC29)

We have studied the genomic organization of human cellular sequences (c-myc) homologous to the transforming gene (v-myc) of avian myelocytomatosis virus (MC29). Southern blotting experiments using v-myc probes showed that several fragments of the human genome contain sequences related to the central part of v-myc but only few of them are homologous to the 3' portion of the viral gene. Several recombinant phages which represent different regions of the genome containing c-myc-related sequences were isolated from a human DNA library. Two clones (lambda-LMC-12 and -41) overlap over approximately 17 kilobases of DNA where a sequence homologous to that of the entire v-myc is present. Restriction mapping experiments and heteroduplex analysis show that c-myc sequences of this locus are interrupted by one intron, suggesting that lambda-LMC-12 and -41 contain the complete functional c-myc gene. Three other clones (lambda-LMC-3, -4, and -26) do not overlap and contain sequences related to only approximately 0.3 kilobase of v-myc but lack 5' and 3' portions of the gene. These sequences are not interrupted by introns and are more divergent from v-myc than is the complete gene, suggesting that they may represent either pseudogenes or parts of distantly related genes.

Molecular cloning of circular unintegrated DNA of two types of the SEATO strain of gibbon ape leukemia virus

Closed circular unintegrated DNA of the SEATO strain of gibbon ape leukemia virus (GaLV-S) was isolated from canine thymus fibroblasts after cocultivation with chronically infected bat lung fibroblasts. Restriction endonuclease HindIII cleaves GaLV-S DNA once, thus allowing isolation and cloning of HindIII-digested unintegrated DNA in a permitted form. Two clones isolated in the vector, Charon 21A, were nearly identical by restriction enzyme mapping to each of the two types of GaLV-S previously observed. These two types differ at a single SalI site. Unlike previous maps of GaLV-S proviral DNA, however, both clones lack SstI sites in the long-terminal-repeat units. Both the GaLV-S clones and the major species of GaLV-S proviral DNA contain an EcoRI site in the long-terminal-repeat units. The presence of this EcoRI site and the absence of an SstI site in the GaLV-S long-terminal-repeat units differentiate it from all other known GaLV strains and from the closely related nononcogenic simian sarcoma-associated virus. Heteroduplex comparisons of each of the two clones to clones of simian sarcoma-associated virus show no obvious deletion or substitution loops. This suggests that the ability of GaLV-S to induce myeloid leukemia in gibbon apes in not due to an acquired onc gene.

Chromosomal assignment of the human homologues of feline sarcoma virus and avian myeloblastosis virus onc genes

Retroviral transforming genes, v-onc genes, are derived from normal cellular sequences that are called cellular onc (c-onc) genes. DNA from mouse-human somatic cell hybrids that have selectively lost human chromosomes was used in Southern blots to map the chromosomal location of two human onc genes. Cloned human homologues of retroviral onc genes were used as probes. Because the human c-fes gene, which is homologous to feline sarcoma virus, segregates concordantly with human chromosome 15, and the human c-myb gene, which is homologous to avian myeloblastosis virus onc genes, segregates concordantly with human chromosome 6, we have assigned the c-fes and the c-myb genes to human chromosomes 15 and 6, respectively. Nonrandom chromosomal defects involving these human chromosomes have been observed in neoplasms. These studies should be valuable in determining whether specific rearrangements involving these chromosomes result in the abnormal expression of these onc genes in human malignancies.

Comparative restriction endonuclease maps of proviral DNA of the primate type C simian sarcoma-associated virus and gibbon ape leukemia virus group

Extrachromosomal DNA was purified from canine thymus cells acutely infected with different strains of infectious primate type C viruses of the woolly monkey (simian) sarcoma helper virus and gibbon ape leukemia virus group. All DNA preparations contained linear proviral molecules of 9.1 to 9.2 kilobases, at least some of which represent complete infectious proviral DNA. Cells infected with a replication-defective fibroblast-transforming sarcoma virus and its helper, a replication-competent nontransforming helper virus, also contained a 6.6- to 6.7-kilobase DNA. These proviral DNA molecules were digested with different restriction endonucleases, and the resultant fragments were oriented to the viral RNA by a combination of partial digestions, codigestion with more than one endonuclease, digestion of integrated proviral DNA, and hybridization with 3'- and 5'-specific viral probes. The 3'- and 5'-specific probes each hybridized to fragments from both ends of proviral DNA, indicating that, in common with those of other retroviruses, these proviruses contain a large terminal redundancy at both ends, each of which consists of sequences derived from both the 3' and 5' regions of the viral RNA. The proviral sequences are organized 3',5'-unique-3',5'. Four restriction enzymes (KpnI, SmaI, PstI, and SstI) recognized sites within the large terminal redundancies, and these sites were conserved within all the isolates tested. This suggests that both the 3' and 5' ends of the genomic RNA of these viruses are extremely closely related. In contrast, the restriction sites within the unique portion of the provirus were not strongly conserved within this group of viruses, even though they were related along most of their genomes. Whereas the 5' 60 to 70% of the RNA of these viruses was more closely related by liquid hybridization experiments than was the 3' 30 to 40%, restriction sites within this region were not preferentially conserved, suggesting that small sequence differences or point mutations or both exist throughout the entire unique portion of the genome among these viruses.

Isolation and identification of lymphocytic and myelogenous leukemia-specific sequences in genomes of gibbon oncornaviruses

Five gibbon ape leukemia virus substrains (two from gibbons with lymphocytic leukemia and three from gibbons with myelogenous leukemia) were examined for unique genomic sequences specific for each form of leukemia. By using sequential adsorption procedures, the genome from each gibbon ape leukemia virus was fractionated into four sets of distinct nucleotide sequences. Based on their hybridization specificities toward DNAs of leukemic tissues, these sequences were designated as follows: (i) "COM," (ii) "LYM" or "MYE," (iii) "UNI," and (iv) "UND." The COM fraction represented sequences common to all of the viral genomes. The LYM fraction, which was isolated only from gibbon ape leukemia viruses associated with lymphocytic leukemia, represented genomic sequences associated with lymphocytic leukemia since the RNA hybridized at a 4- to 15-fold-higher rate to infected tissue DNA from lymphocytic leukemic gibbons than to infected tissue DNA from myelogenous leukemic gibbons. The MYE fraction, which was isolated only from gibbon ape leukemia viruses associated with myelogenous leukemia, represented genomic sequences associated with myelogenous leukemia since the RNA hybridized at a 5- to 15-fold-higher rate to infected tissue DNA from myelogenous leukemic gibbons than to infected tissue DNA from lymphocytic leukemic gibbons. The UNI fraction contained sequences unique to one virus substrain. The UND fraction contained sequences which varied depending upon the substrains involved in the adsorption procedures. These findings suggest that each gibbon ape leukemia virus examined in this study contains subgenomic sequences that are specifically identifiable only with the form of leukemia from which the virus was isolated.

Detection of integrated type-C viral DNA fragments in two primates (human and gibbon) by the restriction enzyme blotting technique

We have shown that 1. partial provirus integration can be a possible result of a natural infection, and may serve as a model in animal systems where a viral etiology is implicated but detection of a major fraction of the virus genome is rare; 2. All human DNA contains some sequences that hybridize specifically with genomes of SiSV-SiSAV, suggesting that viruses of this group have infected humans in the past and recombined with human cellular DNA. 3. Finally, DNA from uncultured leukocytes of two leukemic patients, one being HL23, which yielded the virus HL23V in culture, was shown to have virus specific fragments related to BaEV. Another human DNA sample revealed virus specific fragments related to SiSV(SiSAV). These fragments are probably acquired by infection.