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N Sagata

Publications and source records attributed to N Sagata.

At least 55 records · Page 3Linked to original sources
PubMed1987

Structure of a defective provirus of bovine leukemia virus.

Defective proviruses of bovine leukemia virus (BLV) in the genomes of infected cells were investigated by using Southern blotting hybridization analysis with various portions of a cloned BLV DNA as probes. When nine independent tumors of enzootic bovine leukosis with a single proviral copy per cell were examined, a single defective provirus of BLV was found in one tumor and also in a bovine B cell line derived from this tumor. Hybridization analysis of this defective provirus revealed that it underwent deletion between the pol and env genes and contained no major deletion in the other regions.

Animals↗
PubMed1987

The bovine leukemia virus X region encodes a trans-activator of its long terminal repeat.

We constructed a fusion plasmid, pMX-I, by which the major open reading frame, X-I, of the bovine leukemia virus (BLV) X gene was expressed under control of the mouse metallothionein promoter. pMX-I was cotransfected into CV1 monkey kidney cells together with another construct containing the BLV long terminal repeat (LTR) linked to the chloramphenicol acetyltransferase (CAT) structural gene. The result of assay of CAT synthesis suggests that the X-I product functions as a trans-acting activation factor of the BLV LTR.

Acetyltransferases↗
PubMed1986

Protease gene structure and env gene variability of the AIDS virus.

The protease gene structure and the env gene variability have been precisely compared between the AIDS virus and members of the HTLV/BLV family. The conserved amino acid sequence (LVDT) which is repeated in the proteases of the HTLV/BLV family is not repeated in AIDS virus. Comparative analysis of the env gene sequences reveals the striking fact that the env gene of AIDS virus is 8-12-times more variable than those of the HTLV/BLV family. Within the AIDS virus env gene, the surface glycoprotein region is more liable to vary than is the transmembrane region; unexpectedly, however, this liability is not a characteristic feature of the AIDS virus because it is more prominent in other retroviruses including members of the HTLV/BLV family.

Acquired Immunodeficiency Syndrome↗
PubMed1986

No involvement of bovine leukemia virus in sporadic bovine lymphosarcoma.

Using various portions of a molecularly cloned bovine leukemia virus (BLV) DNA as probes, the possible integration of a BLV genome or a BLV-related sequence into the chromosomal DNA of sporadic bovine leukosis (SBL) tumor cells was investigated by Southern blotting analysis. Under stringent as well as nonstringent conditions of hybridization, neither BLV nor BLV-related sequence specific to SBL DNAs was detected in any SBL tumor examined. These results provide conclusive evidence for lack of the relation of BLV or a BLV-related agent to SBL.

Animals↗
PubMed1985

Two distinct polypeptides may be translated from a single spliced mRNA of the X genes of human T-cell leukemia and bovine leukemia viruses.

Human T-cell leukemia and bovine leukemia viruses have a potential transforming gene, termed X. In addition to the major open reading frame known to encode a functional protein, the X gene harbors another short open reading frame which overlaps this major one. Both of these open reading frames are found on a single spliced X mRNA in a potentially functional form. Circumstantial evidence strongly suggests that they are both translated from the single X mRNA molecule, showing striking similarity to the translation mechanism of an adenovirus Elb gene mRNA. We note that the short open reading frame has the capability to encode a putative nuclear protein with structural features similar to those of an AIDS virus trans-acting protein.

Amino Acid Sequence↗
PubMed1985

Identification and some biochemical properties of the major XBL gene product of bovine leukemia virus.

Using a rabbit antiserum directed against a synthetic oligopeptide whose sequence was deduced from the nucleotide sequence of the XBL gene of bovine leukemia virus, we detected a 38-kDa protein in virus-producing cell lines. In vitro translation of hybrid-selected RNA unequivocally demonstrates that this protein, designated p38(XBL), is indeed encoded by the XBL gene. Unlike the other virus-encoded proteins, however, p38(XBL) resides within the cells without being incorporated into virions. It undergoes no gross post-translational modifications and has a relatively short half-life (5-6 hr) in vivo. Furthermore, cell fractionation combined with pulse-chase experiment reveals that a significant fraction (more than half) of the p38(XBL) localizes to the nucleus of the infected cell after synthesis. We conclude that the XBL gene of bovine leukemia virus is a functional gene encoding a nonvirion protein p38(XBL), which possibly functions within the nucleus of the infected cell to regulate viral or cellular gene expression. p38(XBL) is presumably translated from a doubly spliced, bicistronic mRNA that has the capability to encode another small polypeptide in a different reading frame.

Antibodies, Viral↗
PubMed1985

Complete nucleotide sequence of the genome of bovine leukemia virus: its evolutionary relationship to other retroviruses.

We report the complete 8714-nucleotide sequence of the integrated bovine leukemia virus genome and deduce the following genomic organization: 5' LTR-gag-pol-env-pXBL-3' LTR, where LTR represents a long terminal repeat and pXBL represents a region containing unidentified open reading frames. This genomic structure is similar to that of human T-cell leukemia virus. The LTR contains a putative splice donor site in the R region. The gag gene encodes a precursor protein with the form NH2-p15-p24-p12-COOH. The NH2- and COOH-terminal regions of the pol product show stronger homologies with those of avian, rather than murine, type C retrovirus, and its structure is identical to that of avian virus. The env gene encodes a surface glycoprotein (gp51) and a transmembrane protein (gp30). In contrast to the pol product, the gp30 shows stronger sequence homology with a murine, rather than avian homologue, indicating the chimeric nature of the bovine leukemia virus genome. Comparisons of the best conserved pol sequences and overall genomic organizations between several major oncoviruses allow us to propose that bovine leukemia and human T-cell leukemia viruses constitute a group, designated as type "E," of Oncovirinae.

Amino Acid Sequence↗
PubMed1985

Methylation pattern of the bovine leukemia provirus genome in bovine leukemic cells.

All the known genes of the bovine leukemia proviral genome were found to be heavily methylated in both fresh and short-term-cultured leukemic cells, the latter of which expressed viral antigens. However, the pXBL region appeared to be mostly demethylated or at least hypomethylated in both cells, indicating that there is a non-uniform methylation pattern of the proviral genome.

Animals↗
PubMed1985

[Modified env gene in Friend spleen focus forming virus--structure, origin, and its role in leukemogenesis].

Modified env gene or gp55 gene in Spleen Focus Forming Virus, polycythemic strain, K-1 was molecularly cloned and its structure was characterized gp55 is a fusion glycoprotein consisting of N terminal 2/3 of xenotropic virus-related gp70 and C terminal half of F-MuLV p15E. A unique structure at the 3' and of the gp55 gene with 6 base pairs + 1 base pairs insert was identified. Gp55 may be hooked by the lipid bilayer of the cell membrane of the SFFV-intected cells, and additional glycosylation on the cell surface may modify the growth regulation of the cells. Possible origin of SFFV-specific gp55 gene was discussed.

Animals↗
PubMed1984

Comparison of the entire genomes of bovine leukemia virus and human T-cell leukemia virus and characterization of their unidentified open reading frames.

We have compared the sequence of the entire genomes of bovine leukemia virus (BLV) and human T-cell leukemia virus type I (HTLV-I). Both the gag and pol genes show overall strong homologies indicating the close evolutionary relationship of the two retroviruses. However, a surface glycoprotein portion of the env gene shows no appreciable homology, which probably reflects a difference in their host ranges. The 3' end portion of the BLV genome (designated as pXBL) contains an unidentified long open reading frame that has a typical protein-coding property. The potential product of this open reading frame may be a glycoprotein of approximately 40 000 daltons. We note that its amino acid sequence shows low but appreciable homology, especially in its N-terminal quarter, to that of the HTLV-I counterpart (pX product), and we thus suggest that BLV pXBL and HTLV-I pX have diverged from a common ancestral gene. It is tentatively concluded that both the putative pXBL and pX products are respectively produced from a spliced mRNA.

Amino Acid Sequence↗
PubMed1984

Identification of a potential protease-coding gene in the genomes of bovine leukemia and human T-cell leukemia viruses.

The genomes of bovine leukemia and human T-cell leukemia viruses both contain an unidentified region between the gag and pol genes. These regions harbor an open reading frame that is in a different phase from the reading frames of the gag and pol genes. Based on the deduced amino acid sequences, we show here that they potentially encode a gag precursor-cleaving protease, which is known to be fused to the gag and pol products of avian and murine retroviruses, respectively. This finding raises the interesting question of the expression and evolution of retroviral genes.

Amino Acid Sequence↗
PubMed1984

env-Related leukemogenic genes (gp55 genes) of two closely related polycythemic strains of Friend spleen focus-forming virus possess different recombination points with an endogenous mink cell focus-forming virus env gene.

The unintegrated circular provival DNA of the replication-competent, helper Friend murine leukemia virus (F-MuLV) in a polycythemic strain of Friend leukemia virus complex (FLV, K-1 strain) was molecularly cloned after insertion into the EcoRI site of the plasmid pBR322. The nucleotide sequence of its env gene has been determined. Sequences of this F-MuLV env gene, and the previously reported env-related gene (gp55 gene) of Friend spleen focus-forming virus (SFFV) (K-1 strain) were compared to that of the same gene of the other polycythemic SFFV isolate, SFFV (502), recently reported by Clark and Mak. The gp55 genes of the two SFFV isolates are almost identical to each other and have several common characteristic structures. However, the two gp55 genes are different in that the gp55 gene of SFFV (K-1) has a longer nonecotropic MuLV env sequence than that of SFFV (502). This finding may suggest that each SFFV isolate has been generated independently by recombination between a putative defective variant of F-MuLV and an endogenous mink cell focus-forming virus env sequence.

Amino Acid Sequence↗
PubMed1984

Bovine leukemia virus: unique structural features of its long terminal repeats and its evolutionary relationship to human T-cell leukemia virus.

The nucleotide sequence of the long terminal repeat (LTR) of bovine leukemia virus, a unique oncogenic retrovirus of cattle, was determined. The LTR consisted of 530 base pairs (bp) with an inverted repeat of 6 bp at its 5' and 3' ends, flanked by a direct repeat of 6 bp of host cell origin. A tRNAPro binding site for minus-strand DNA synthesis followed the 5' LTR. The U3 region contained putative transcriptional promoters, "CAT" box and "TATA" box, but they had peculiar sequences (C-C-A-A-C-T and G-A-T-A-A-A-T). The U3 region also contained a potential enhancer element, whose sequence partially resembled those of other viral and cellular, especially of immunoglobulin, enhancers. The most striking structural feature of the LTR was an exceptionally long R region (228 bp), which separated a poly(A) addition signal (A-A-T-A-A-A) from a poly(A) site as far apart as 260 bp. The long R region was suggested to form a large stable hairpin structure on a nascent RNA chain, making the two transcription termination signals close together and thus ensuring normal termination of the chain. This structural feature of the bovine leukemia virus LTR was analogous to that of human T-cell leukemia virus LTR and, in fact, slight sequence homology (at most 50%) was observed between the R regions of these two retroviruses, indicating their evolutionary relationship. The unique structural feature of bovine leukemia virus and human T-cell leukemia virus LTRs may thus bear some relation to the biological features commonly shared by these retroviruses.

Base Sequence↗
PubMed1984

BLV and HTLV-I: their unique genomic structures and evolutionary relationship.

We have compared the sequences of the entire genomes of bovine leukemia virus (BLV) and human T-cell leukemia virus type I (HTLV-I). Both the gag and pol genes show overall strong homologies between the two retroviruses, indicating their close evolutionary relationship. However, a surface glycoprotein portion of the env gene shows little if any homology, probably reflecting a difference in their host range. These retroviruses appear to harbour a gag precursor-cleaving protease, a not yet experimentally identified viral protein, between their gag and pol genes. Most interestingly, the 3' end portion of the BLV genome (designated pXBL) contains a long open reading frame that has a typical protein-coding property. The product of this open reading frame has now been identified as a protein of 38,000 daltons, which is produced by a spliced mRNA. We note that its amino acid sequence shows appreciable homology, especially in its N-terminal quarter, to that of the HTLV-I counterpart (pX), and we thus suggest that BLV pXBL and HTLV-I pX has diverged from a common ancestral gene. Finally and very importantly, comparisons of the best conserved pol sequences and overall genomic organizations between BLV and several other oncoviruses allow us to propose that BLV and HTLV-I constitute a novel group of Oncovirinae, designated here as type "E."

Biological Evolution↗
PubMed1983

Molecular cloning of bovine leukemia virus DNA integrated into the bovine tumor cell genome.

The bovine leukemia virus (BLV) DNA harbored in the bovine tumor cell genome was cloned in lambda Charon 4A phage. Using either representative or 3' half-enriched BLV cDNA as a blot hybridization probe, clone lambda BLV-1 was shown to carry 9 kb of the BLV genome, flanked by cellular sequences at both ends. Restriction mapping with twelve endonucleases and hybridization of the DNA fragments to BLV cDNA representing a 3'-end portion of the viral genome revealed the presence and precise location of two long terminal repeats (LTRs) and virus-cell junctions. Thus, lambda BLV-1 appears to contain the complete BLV genome and flanking tumor cellular sequences. The restriction map of the cloned BLV proviral DNA closely resembles that previously reported for unintegrated linear proviral DNA, but differs significantly from that of the integrated provirus of another BLV isolate, the difference occurring preferentially in the putative gag and pol genes.

Animals↗
PubMed1983

Complete nucleotide sequence of the gene for the specific glycoprotein (gp55) of Friend spleen focus-forming virus.

The complete nucleotide sequence of the gene for the specific glycoprotein (gp55) of the polycythemic strain of Friend spleen focus-forming virus (SFFV) was derived from the cloned SFFV DNA intermediate. The gp55 gene is present within 1.4 kilobases of the 5' side of the 3'long terminal repeat sequence. The open reading frame predicts the primary translation product has a total of 409 amino acids with a Mr of 44,752. Comparisons of the deduced amino acid sequence of gp55 with those of the envelope (env) gene products of murine leukemia viruses (MuLVs) revealed that gp55 is composed of three distinct regions. The amino-terminal 80% of the molecule has a high degree of sequence homology with the amino-terminal portion of the gp70 of the Moloney mink cell focus-forming virus (BALB/Mo-MCFV). This portion of the BALB/Mo-MCFV gp70 is known to be coded for by the acquired xenotropic env-like sequence. The sequence of the following 66 amino acids of gp55 is highly homologous to that of the middle portion of the p15E of Moloney MuLV (Mo-MuLV). The sequence of the Carboxyl-terminal 12 amino acids is specific to gp55 and a comparison of the nucleotide sequence showed that this specific amino acid sequence is due to the presence of seven extra nucleotides compared with the sequence of the Mo-MuLV.

Amino Acid Sequence↗
PubMed1982

Integration of bovine leukemia virus DNA in the genomes of bovine lymphosarcoma cells.

Integration of bovine leukemia virus (BLV) in the genomes of infected cells was investigated in cattle with enzootic bovine leukosis (EBL) and sporadic bovine leukosis (SBL). Southern blot hybridization of BLV cDNA to Eco RI and Xba I restriction fragments of EBL tumor DNAs revealed that: 1) one to four or more copies of proviral DNA were integrated per genome; 2) the restriction pattern of the integrated proviral DNA was the same in two or three different tumors from the same animals; and 3) different patterns were observed among tumors from four different animals. These findings suggest the monoclonal origin of different tumors in an individual animal and the existence of multiple chromosomal integration sites of BLV provirus. DNAs from several SBL tumors were also analyzed with the same restriction enzymes, but with both representative and cDNA3'-enriched's of BLV RNA. No hybridization bands reactive with representative BLV cDNA could be detected, while several bands appeared to hybridize with cDNA3'-enriched.

Animals↗