Integration of Bovine Leukemia Virus DNA in the Genomes of Bovine Lymphosarcoma Cells

Abstract

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: I) 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.

Integration of bovine leukaemia virus at all stages of enzootic bovine leukosis

“…In tumour tissue, integrated provirus has been reported to occur in most cells, but at only a small number of sites in the genome [14]. Onuma et al [20] showed that tumours were of monoclonal origin in an individual animal, but different integration patterns existed among tumours from different animals.…”

Molecular Cloning and Sequencing of an Australian Isolate of Proviral Bovine Leukaemia Virus DNA: Comparison with other Isolates

“…Tumour tissue contains one to four BLV proviral copies per genome, at very few sites (Kettmann et al, 1979(Kettmann et al, , 1980Onuma et al, 1982), and at a large number of sites in a quarter to a third of circulating leukocytes (Kettmann et al, 1980). There is no evidence of a preferential integration site for the provirus (Kettmann et al, 1983 ;Gregoire et al, 1984), thus diminishing the possibility of BLV exerting its transforming effect by downstream promotion of a particular proximal cellular sequence.…”

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

“…Curiously, its productively infected cell line has rarely been established (13) and, in fact, it does not replicate efficiently in the natural target B lymphocytes (14). Finally, BLV is not integrated into a common site in the tumor cell chromosome (15,16) and does not activate a downstream host cell gene (14). In the present study, we examined the nucleotide sequence of the cloned BLV LTR, which we expected to show some unique structural features, because of its essential role in viral replication.…”