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Preferential transcription of HTLV-I LTR in cell-free extracts of human T cells producing HTLV-I viral proteins.

The promoters of the adenovirus 2 major late gene, the mouse beta-globin gene, the mouse immunoglobulin VH gene and the LTR of the human T-lymphotropic retrovirus type I were tested for their transcription activities in cell-free extracts of four cell lines; HeLa, CESS (Epstein-Barr virus-transformed human B cell line), MT-1 (HTLV-I-infected human T cell line without viral protein synthesis), and MT-2 (HTLV-I-infected human T cell line producing viral proteins). LTR was preferentially transcribed in the extracts of MT-2 although the other three genes were transcribed with relatively constant efficiencies in different extracts. The results agree well with the previous in vivo studies on the promoter activity of HTLV-I LTR. Mixing of HeLa and MT-2 extracts revealed the presence of a LTR-specific stimulating activity in MT-2 extracts.