Physical Map of the Ribosomal Ribonucleic Acid Gene from Tetrahymena pyriformis

A physical map of the rRNA gene from the ciliated protozoan Tetrahymena pyriformis has been determined. The isolated rDNA palindrome was labeled by nick translation and digested with the sequence-specific endonucleases KpnI, BeII, PvuII, PstI, SstI, AvaI, AvaII, HpaI, BamIII, BgIII, or Him1III, and the molecular weights of the products were determined by gel electrophoresis. The DNA fragments generated by digestion with each endonuclease were ordered into a unique sequence either by analyzing the products produced by concomitant cleavage with one or more additional restriction enzymes or by hybridizing to 17S and 25S rRNA. Hybridization of the 35S rRNA primary transcription product to HinAlll and BamHl restriction fragments localizes the promoter to the left of 16.9% and the terminator to the region between 71.6% and 78% on the physical map.