p21rex protein of HTLV-1

Virion protein expression of the human T-cell leukemia virus type 1 (HTLV-1) is regulated by p27rex. This protein is expressed by a doubly spliced mRNA encoding an additional protein, p21rex. p27rex has been shown to increase the amount of unspliced viral mRNAs encoding envelope and capsid proteins. To assess a possible contribution of p21rex to the rex regulation, a point mutation was introduced into the p21rex initiation codon. Expression of env and gag plasmids, transfected in Jurkat cells, was dependent only upon p27rex expression and was not affected by the absence of p21rex. Consequently, the rex regulation of the HTLV-1 structural genes can be solely attributed to the p27rex protein.