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

Abstract

Human retrovirus adult T-cell leukemia virus (ATLV) has been shown to be closely associated with human adult T-cell leukemia (ATL). 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 9032 bases of the proviral genome was determined. The provirus DNA contains 2 long terminal repeats (LTR) 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 3 large open reading frames, which are capable of coding for proteins of 48,000, 99,000 and 54,000 daltons. The 3 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 3 open frames, the ATLV sequence has 4 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.