Subcellular localization of the product of the long open reading frame of human T-cell leukemia virus type I.

Human T-cell leukemia virus type I (HTLV-I) is a retrovirus associated with adult T-cell leukemia and lymphoma. In addition to containing the gag, pol, and env genes of the chronic leukemia viruses, the genome of HTLV-I contains a long open reading frame (LOR) located between the 3' end of the envelope gene and the 3' long terminal repeat sequence (LTR). It has been suggested that a protein of 42 kilodaltons that is encoded by the LOR region may participate in both trans-acting transcriptional regulation of the viral LTR as well as in the transforming properties of HTLV-I. It is reported here that a significant fraction of the 42-kilodalton HTLV LOR product is located in the nucleus of HTLV-I-infected transformed lymphocytes, a finding that is consistent with its proposed functions.