2 CIS-ACTING SIGNALS CONTROL RIBOSOMAL FRAMESHIFT BETWEEN HUMAN T-CELL LEUKEMIA-VIRUS TYPE-II GAG AND PRO GENES

The open reading frame of the human T-cell leukemia virus type II pro gene is arranged at a - 1 position relative to the gag gene. Synthesis of the Gag-Pro fusion polyprotein is facilitated by ribosomal framesh ift into the reading frame of the pro gene. Cloning of a synthetic 41- bp oligonucleotide corresponding to the gag-pro junction within a hete rologous gene (nef of human immunodeficiency virus type I) and mutatio n analysis revealed that two cis-acting signals, an adenosine residue stretch and a dyad symmetry sequence, flanking the UAA termination cod on, are required for efficient ribosomal frameshifting between gag and pro. The stability of the stem-loop structure is crucial for frameshi fting.