A synthetic tyrosine suppressor tRNA gene with an altered promoter sequence. Its cloning and relative expression in vivo.

The total synthesis of a tyrosine suppressor tRNA gene with a modified promoter is described. The alteration involves the replacement of the four G:C base pairs immediately preceding the start point of transcription by A:T base pairs. The new sequence contains the recognition sequence for the HindIII restriction endonuclease at the transcriptional start point, thus permitting fusion of the structural gene with promoters containing independent sequence modifications. The construction, cloning, and biological activity of several recombinant DNAs containing the tRNA gene with the modified promoter are described. The expression of this gene in vivo is compared with that of both the unmodified synthetic suppressor gene and a naturally occurring tyr su3+ gene cloned onto a multicopy plasmid.