A retrovirus causing leukaemia and sometimes a mild immunodeficiency. In addition to gag, pol and env, the virus carries a coding sequence pX that does not seem to have a normal genomic homologue and is not a conventional oncogene. The protein product of the pX region is a short-lived nuclear protein (around 40 kD). T-cells transformed with HTLV-1 continue to proliferate and are independent of interleukin-2.
Dictionary of molecular biology. 2004.