The nucleotide sequence of the putative transcription initiation site of a cloned ribosomal RNA gene of the mouse

Abstract
Approximately one kilobase pairs surrounding and upstream the transcription initiation site of a cloned ribosomal DNA (rDNA) of the mouse were sequenced. The putative transcription initiation site was determined by two independent methods: one nuclease S1 protection and the other reverse transcriptase elongation mapping using isolated 45S ribosomal RNA precursor (45S RNA) and appropriate restriction fragments of rDNA. Both methods gave on identical result; 45S RNA had a structure starting from ACTCTTAG---.