[Primary structure of the 3'-terminal region of the cloned DNA of the bovine leukemia virus].

The nucleotide sequence of the 3'-terminal region of the cloned bovine leukaemia virus cDNA (1474 bp) was elucidated using both Sanger and Maxam-Gilbert techniques. This DNA region contains U3 and R parts of the BLV LTR and an upstream sequence with four open reading frames (ORF) of unknown function. The comparison of the nucleotide substitutions in these ORF with the two variants of proviral BLV DNA suggests that the only pX1 ORF possesses a coding function. The role of the pX1 protein is discussed.