Figure 4.

HTLV-1 viral RNA splicing and Tax oncogene expression. (A) Functional domains and motifs are indicated for the HTLV-1 Tax oncoprotein. (B) Alternative RNA splicing products of HTLV-1 viral genes. Seven positive-strand transcripts (1-E, 1-2-3, 1-2-A, 1-A, 1-2-B, 1-C and 1-3) and one negative strand transcript (HBZ) are produced by alternative RNA splicing of the transcripts derived from either a 5′ or 3′ long terminal repeat (LTR). The HTLV-1 Tax ORF in blue is present in the 1–2–3 mRNA, which is spliced from the nt 119 5′ ss to the nt 4641 3′ ss and then from the nt 4831 5′ ss to the nt 6950 3′ ss. Nucleotide positions are numbered according to the HTLV-1 genomic RNA sequence, starting from the first nucleotide in the pre-mRNA.¹⁵³