Figure 2. Pre-rRNA processing in human cells.
The early 47S precursor is processed along different pathways depending on the order of the cleavages. Given the higher abundance of 30S pre-rRNA relative to the 41S species, cleavage of the ITS1 at site 2 appears to occur most frequently before processing of the 5′-ETS. Arrowheads indicate the pre-rRNA endonucleolytic cleavage sites, although some processing steps involve exonucleases rather than endonucleases. Dashed lines indicate the hypothetical pathway induced by RPL26 depletion.