Primary sequence of the 5'-terminal region of mouse 18 S rRNA and adjacent spacer. Implications for rRNA processing.

Among the stepwise cleavage reactions involved in the processing of rRNA precursors in mammalian cells, an early event corresponds to the removal of the so-called 'external transcribed regions' which are located upstream 18 S rRNA sequence within the primary transcript. We have determined the primary sequence of the domain of mouse pre-rRNA which encompasses this early processing site and analyzed its structural features with reference to the other eukaryotic homologs available. The potential involvement of secondary structure features of rRNA precursors in the recognition process for cleavage is discussed.