Adult T-cell leukemia-like disease in monkey naturally infected with simian retrovirus related to human T-cell leukemia virus type I

Spontaneous T-cell leukemia similar to human adult T-cell leukemia (ATL) was found in an African green monkey naturally infected with simian retrovirus closely related to human T-cell leukemia virus type I (HTLV-I). Monoclonal integration of the simian retrovirus was detected in the primary leukemic cells, suggesting an association of the retrovirus with ATL-like leukemia in the monkey.

Sequence homology of the simian retrovirus genome with human T-cell leukemia virus type I

A retrovirus highly related to human T-cell leukemia virus type I (HTLV-I) was isolated from a T-cell line established from a seropositive pig-tailed monkey and the provirus genome was molecularly cloned using HTLV-I as a probe. The monkey virus (STLV) had the genomic structure of the LTR-gag-pol-env-pX-LTR. Analysis of the env-pX-LTR region revealed the 90% homology of the nucleotide sequence with that of HTLV-I in each region. This high homology of the sequence indicates that STLV is a member of the HTLV family, but apparently different from HTLV-I. This suggests that the possibility of recent interspecies transmission from monkeys to humans in the endemic area is very small. From its similarity to HTLV, STLV should be useful as an animal model in studies on natural HTLV infection and leukemogenesis of HTLV in humans.

Expression of the pX gene of HTLV-I: general splicing mechanism in the HTLV family

Human T-cell leukemia virus type I (HTLV-I) is an etiological agent of adult T-cell leukemia. A viral gene pX encodes for p40X and it has been proposed that this protein trans-activates the viral long terminal repeat and possibly some cellular genes; this activation may be associated with T-cell transformation. The mechanism of pX gene expression and the primary structure of p40X are now reported. Two-step splicing generates the 2.1-kilobase pX mRNA; the initiator methionine for env becomes part of the pX protein. These splicing signals are conserved among all members of the HTLV family except for the acquired immune deficiency syndrome-associated viruses.

Detection and characterization of simian retroviruses homologous to human T-cell leukemia virus type I

Lymphoid cell lines were established from five different species of monkeys which were positive in antibodies cross-reactive with human T-cell leukemia virus type I (HTLV-I) and were shown to contain provirus sequences homologous to HTLV-I. Gene-specific probes of HTLV-I, gag, pol, env, pX, and LTR, hybridized efficiently with monkey DNAs from these cell lines under stringent conditions, indicating that the proviruses are very similar to HTLV-I along with whole viral genomes. However, the preliminary restriction mapping turned out the difference between simian retroviruses and HTLV-I and also among simian retroviruses. These findings suggest a common ancestor of simian and human retroviruses, but exclude the recent interspecies transmission between monkeys and humans.

Envelope proteins of human T-cell leukemia virus: expression in Escherichia coli and its application to studies of env gene functions

The DNA fragments of the 5' and 3' halves of the putative env gene predicted from the DNA sequence of human T-cell leukemia virus (HTLV) provirus were inserted into expression vectors pORF2 and pORF1, respectively, and two hybrid proteins composed of env polypeptides and beta-galactosidase were efficiently produced in Escherichia coli. The hybrid proteins containing the NH2-terminal (EH9) and COOH-terminal (EA1) halves were both immunologically reactive with sera from adult T-cell leukemia patients, demonstrating the utility of the hybrid proteins for diagnosis of HTLV infection. Rabbit antisera against these hybrid proteins detected the two glycoproteins gp62 and gp46, which were previously identified as HTLV env gene products. With these rabbit antisera, two properties of the env gene products were studied. (i) The antisera inhibited syncytia formation of cat S+L- cells induced by HTLV, suggesting that one or both of the env gene products of HTLV, gp62 and gp46, are involved in induction of cell fusion. (ii) The env product gp62 or gp46 or both products are exposed on the surface of HTLV-infected cells and might modulate the proliferation of HTLV-infected T cells in the host because the antisera against the hybrid proteins were cytotoxic on HTLV-producing cell lines. The latter conclusion also is supported by the fact that adult T-cell leukemia patients and healthy HTLV carriers have antibodies to the env gene products.

Identification of a protein (p40x) encoded by a unique sequence pX of human T-cell leukemia virus type I

A protein p40x was identified as a product encoded by frame IV in the pX region of human T-cell leukemia virus type I. Sera from patients with adult T-cell leukemia contained antibodies against p40x, indicating its expression in vivo. The occurrence of splicing to form pX mRNA is proposed and the possible significance of p40x is discussed.

Identification of gag and env gene products of human T-cell leukemia virus (HTLV)

The gag and env gene products of human T-cell leukemia virus (HTLV) were identified with rabbit antisera against the synthetic peptides and a polypeptide produced in Escherichia coli, which corresponded to parts of the proteins predicted from the nucleotide sequence of HTLV [M. Seiki, S. Hattori, Y. Hirayama, and M. Yoshida (1983). Proc. Natl. Acad. Sci. USA 80, 3618-3622]. Viral proteins were detected by immunoprecipitation in two HTLV-producing cell lines. The precursor of gag products was a protein with an apparent molecular weight of 53,000 (Pr53), and was shown to be processed into three mature gag proteins, p19, p24, and p15, in this order, from the 5' end of the gag gene. The processing sites were confirmed to be the same as those predicted from the nucleotide sequence. The env gene product was identified as a glycoprotein of 62,000 Da (gp62), which was processed into gp46 and p20E. All the viral antigens described above were also detected with sera from ATL patients, indicating that all these proteins are expressed in the patients.

Nonspecific integration of the HTLV provirus genome into adult T-cell leukaemia cells

Human T-cell leukaemia virus (HTLV), previously also reported as ATLV, is a recently identified retrovirus which is closely associated with adult T-cell leukaemia (ATL) endemic in southwestern Japan and the Caribbean. Determination of the total nucleotide sequence of the HTLV genome has revealed no typical onc gene acquired from the cellular sequence. Screening of the HTLV provirus genome in tumour cells has shown that in all cases of ATL examined, the primary tumour cells contained the provirus genome and were monoclonal with respect to the integration site of the provirus. These findings suggest that ATL leukaemogenesis may be due to insertional mutagenesis in which the provirus genome is integrated into a specific locus on the chromosomal DNA and then activates an adjacent cellular onc gene, a mechanism already demonstrated in avian lymphoma and erythroblastosis induced by avian leukosis viruses. A common site of HTLV provirus integration in leukaemic cells among some ATL patients was reported by Hahn et al. but subsequently retracted. However, this retraction does not imply the random integration of the proviruses. Independently, we have been testing this insertional mutagenesis model in ATL and report here that the provirus did not have a common locus of integration in 35 ATL patients and did not integrate on the same chromosome in 2 ATL patients.

The detection of human T cell leukemia virus proviral DNA and its application for classification and diagnosis of T cell malignancy

Adult T cell leukemia virus (HTLV or ATLV) proviral DNA integrated in the cellular DNA was examined by a modified Southern blotting method in the peripheral blood mononuclear cells and/or lymph node cells from 61 patients with adult T cell leukemia (ATL) and other hematologic diseases. Serum antibodies against ATL-associated antigens (ATLA) were also examined. The presence of human T cell leukemia virus (HTLV) proviral DNA was confirmed in all 20 patients with overt ATL and in 3 patients with T cell malignant lymphoma, who were seropositive but did not show clinical features characteristic of prototypic ATL. However, it was not detected in 6 antibody-positive healthy individuals and 8 seropositive patients with various hematologic disorders. Thus, the detection of proviral DNA by the method described here seems to be useful for the diagnosis of ATL in the endemic area and may provide a powerful tool for the classification of T cell malignancies.

Monoclonal integration of human T-cell leukemia provirus in all primary tumors of adult T-cell leukemia suggests causative role of human T-cell leukemia virus in the disease

The genome of human T-cell leukemia virus (HTLV) was surveyed in fresh tumor cells of 163 patients with lymphoma and leukemia from the southwest part of Japan where adult T-cell leukemia (ATL) is endemic. Leukemic cells of all 88 cases of ATL tested so far were found to contain the provirus genome and also found to be monoclonal with respect to the integration site of provirus genome. In most cases of ATL, leukemic cells contained one or two copies of the complete HTLV provirus genome, and it was shown that the single species of HTLV with a fully determined sequence is typical in ATL. Some cases of T-cell malignancies, diagnosed as chronic lymphocytic leukemia or non-Hodgkin lymphoma, also had the provirus genome in their tumor cells, whereas some cases with the same diagnosis did not. No cases of other types of lymphoma or leukemia contained the provirus genome in their tumor cells. Monoclonal integration of the HTLV provirus genome in all primary tumor cells of ATL not only indicates that HTLV directly interacts with target cells, which become leukemic, and that integration of the provirus genome is a prerequisite for development of ATL and possibly other related diseases but also indicates that the virus is not associated with other types of lymphoma or leukemia.

HTLV type I (U. S. isolate) and ATLV (Japanese isolate) are the same species of human retrovirus

Two independent isolates of human leukemia virus, human T-cell leukemia virus (HTLV) and adult T-cell leukemia virus (ATLV), are shown to be the same by blotting analysis using gene-specific probes and restriction enzymes. Therefore, Japanese ATL virus and Caribbean HTLV type I, which are exogenous for human, have a common origin.

Identification of envelope glycoprotein encoded by env gene of human T-cell leukemia virus

Envelope gene product of human T-cell leukemia virus was identified as a glycoprotein with an apparent molecular weight of 62,000 daltons, by using rabbit antiserum against a synthetic decapeptide whose structure had been predicted from the nucleotide sequence. Sera from patients with adult T-cell leukemia also reacted with this glycoprotein.

Human adult T-cell leukemia virus: complete nucleotide sequence of the provirus genome integrated in leukemia cell DNA

Human retrovirus adult T-cell leukemia virus (ATLV) has been shown to be closely associated with human adult T-cell leukemia (ATL) [Yoshida, M., Miyoshi, I. & Hinuma, Y. (1982) Proc. Natl. Acad. Sci. USA 79, 2031-2035]. The provirus of ATLV integrated in DNA of leukemia T cells from a patient with ATL was molecularly cloned and the complete nucleotide sequence of 9,032 bases of the proviral genome was determined. The provirus DNA contains two long terminal repeats (LTRs) consisting of 755 bases, one at each end, which are flanked by a 6-base direct repeat of the cellular DNA sequence. The nucleotides in the LTR could be arranged into a unique secondary structure, which could explain transcriptional termination within the 3' LTR but not in the 5' LTR. The nucleotide sequence of the provirus contains three large open reading frames, which are capable of coding for proteins of 48,000, 99,000, and 54,000 daltons. The three open frames are in this order from the 5' end of the viral genome and the predicted 48,000-dalton polypeptide is a precursor of gag proteins, because it has an identical amino acid sequence to that of the NH2 terminus of human T-cell leukemia virus (HTLV) p24. The open frames coding for 99,000- and 54,000-dalton polypeptides are thought to be the pol and env genes, respectively. On the 3' side of these three open frames, the ATLV sequence has four smaller open frames in various phases; these frames may code for 10,000-, 11,000-, 12,000-, and 27,000-dalton polypeptides. Although one or some of these open frames could be the transforming gene of this virus, in preliminary analysis, DNA of this region has no homology with the normal human genome.

Intraduodenally administered 14C-urokinase in Macaca Irus revealed by autoradiography

Intraduodenally administered 14C-urokinase (14C-UK) was located in Macaca Irus by autoradiography. Sagittal sections, approximately 40 micron thick, of a frozen monkey were applied against X-ray films. Autoradiograms thus obtained indicated that a part of intraduodenally administered 14C-UK was incorporated into the systemic blood circulation by transintestinal mucosal membrane.

Replication origin region of Bacillus subtilis chromosome contains two rRNA operons

The first replicating DNA fragment (BamHI-7) of the Bacillus subtilis chromosome contains two promoters for a rRNA operon. A map of restriction enzyme cleavage sites of the region of replication origin suggests the presence of a second rRNA operon in this region. Hybridization of rRNA genes (rDNA) with DNA fragments derived from the origin region by treatment with various enzymes clearly revealed two rRNA operons in this region, one at the B7-B3 junction and the other at the B5-B6 junction. The restriction enzyme cleavage sites surrounding the rRNA operons show that the operon at the B5-B6 junction corresponds to the rrnA operon. A novel operon at the B7-B3 junction was termed rrnO. Transformation by density-labeled fragments of the origin region showed that the first replicating marker, guaA, is located in the B3 fragment. From these results, a map was constructed for the first time to correlate the genetic markers with the physical structure of the replication origin region of the B. subtilis chromosome. The role of the rrnO operon in regulating the initiation of chromosomal replication is discussed, based on the fact that the promoter of the rrnO operon suppresses the replication of the plasmid carrying the promoter.

Human adult T-cell leukemia virus: molecular cloning of the provirus DNA and the unique terminal structure

Adult T-cell leukemia virus (ATLV) is a human retrovirus closely associated with adult T-cell leukemia. The integrated provirus DNA and cDNA from virion RNA were molecularly cloned and their structures were analyzed. Clone lambda ATM-1 of an integrated provirus DNA in the MT-1 cell line, established from adult T-cell leukemia cells by cocultivation with cord lymphocytes, contained DNA about 13,000 base pairs (bp) long and long terminal repeats (LTR) at both ends of the viral sequence that were about 8,000 bp long. These two LTR sequences were linked to cellular sequences with direct repeats of 7 bp. Each LTR consisted of 754 bp including inverted repeats of 2 bp at the ends and the T-A-T-A-A box, characteristics in common with those of LTRs of other known retroviruses. Adjacent to the 5' LTR there was a sequence identical to the tRNAPro binding site in murine leukemia virus, suggesting that tRNAPro is a primer for reverse transcription of the viral genome. From these structural features, the mechanism of ATLV replication was suggested to be the same as that of other known animal retroviruses. However, the length of the small terminal repeats at the ends of the RNA genome, 228 +/- 1 bases, is much longer than the lengths, up to 80 bases, of those in avian, mouse, or primate retroviruses so far analyzed. These findings suggest that ATLV should be classified in a distinct group of retroviruses with bovine leukemia virus which also makes unusually long strong-stop cDNA.

Identification of a suppressor sequence for DNA replication in the replication origin region of the Bacillus subtilis chromosome

The first replicating fragment of the Bacillus subtilis chromosome, B7, inhibited the replication of the plasmid that carried this fragment. In earlier work using sequential cleavage by Alu I, the suppressor function was located within a 489-base-pair segment. The nucleotide sequence of the entire segment now has been determined. The sequence is characterized by two promoter-like structures and several putative recognition sequences, such as termination signals, 2-fold symmetries, inverted repeats, and repeats. By means of sequential cleavage with exonuclease BAL-31, the essential region for suppression was located in a 200-base-pair region that contains the two promoters with the same orientation. Specific transcription was produced in vitro by using B. subtilis or Escherichia coli RNA polymerases. The transcription was mostly from the second promoter. Elimination of the -35 region of the second promoter dramatically affected both inhibitory activity and in vitro transcription, suggesting that the transcriptional activity of the second promoter is involved in the cis-inhibition of DNA replication. The significance of the suppressor sequence in the region of the replication origin of the B. subtilis chromosome is discussed.

Structure and function of the region of the replication origin of the Bacillus subtilis chromosome. I. Isolation and characterization of plasmids containing the origin region

A BamHI restriction endonuclease fragment, B7, which is replicated first among all other fragments derived from the Bacillus subtilis chromosome, was cloned in Escherichia coli using as vector a hybrid plasmid pMS102 that can replicate both in E. coli and B. subtilis. Digestion of pMS102 with BamHI produced two fragments and the smaller one was replaced by the B7 fragment. The cloned plasmid pMS102'-B7 exhibited some peculiar properties that were not observed with plasmids containing other fragments from the B. subtilis chromosome. (1) E. coli cells harboring this plasmid stuck to each other and to glass. This property was more apparent when cells were grown in poor media. (2) E. coli cells tended to lose the plasmid spontaneously when they were grown without the selective pressure favorable to the plasmid. (3) The frequency of transformation of B. subtilis by pMS102'-B7 was less than 1/1,000 of that by the vector plasmid pMS102'. The number of copies of pMS102'-B7 present in the transformants was also markedly reduced, although the pUB110 origin of replication on the vector was intact and should be functional in B. subtilis. This inhibitory effect of the B7 fragment on plasmid replication was confirmed more directly by developing a semi in vitro replication system using protoplasts. Both in E. coli and B. subtilis the B7 fragment affected replication of its own molecule but not that of the coexisting plasmid with an identical replication system. The implication of the function of the B7 fragment in the initiation of the B. subtilis chromosome will be discussed.

Structure and function of the region of the replication origin of the Bacillus subtilis chromosome. II. Identification of the essential regions for inhibitory functions shown by the DNA segment containing the replication origin

A BamHI restriction endonuclease fragment B7, which contains the replication origin of the Bacillus subtilis chromosome, showed inhibitory effects on cell growth and plasmid replication in Escherichia coli and Bacillus subtilis, when B7 was inserted into a composite plasmid pMS102' and introduced into these cells. In order to localize these properties in more limited regions within the B7 fragment, we developed a new and widely applicable method for deletion of DNA segments of various lengths from one or other end of a given region of the plasmid molecule. Using a set of deletions in the B7 fragments of pMS102'-B7, we determined the loci responsible for the inhibitory effects of B7 as described below. (1) Stickiness appearing in E. coli cells was caused by a segment residing in a region of approximately 2.2 kilobase pairs (kbp) overlapping the E19 and E22 fragments. (2) instability of the plasmid in E. coli was due to a segment localized in the 440 bp region of the E19-side terminal portion of the 2.2 kbp region. (3) The same 440 bp were also responsible for inhibition of the replication of the plasmid in B. subtilis. Hybridization of the cloned DNA fragments containing the 2.2 kbp region with the whole B. subtilis chromosome revealed that several regions of the chromosome are homologous to this characteristic sequence.