In vitro transcription of cloned yeast ribosomal DNA by yeast RNA polymerase A

Summary A hybrid plasmid, containing yeast ribosomal DNA, was transcribed by purified yeast RNA polymerase A in the presence of the stimulation factor P37. The transcription was not random. The yeast sequences were copied highly asymetrically, as shown by competition hybridization with yeast ribosomal RNA. Using the same DNA, truncated by different restriction enzymes, it appeared, however, that the in vitro preferential initiation region was located upstream of the presumptive in vivo initiation site for the 37S pre-rRNA.