 There are 11 pseudouridines in the "Escherichia coli" rRNA, 30 in yeast cytoplasmic rRNA and a single modification in mitochondrial 21S rRNA and about 100 pseudouridines in human rRNA indicating that the extent of pseudouridylation increases with the complexity of an organism.Pseudouridine in rRNA and tRNA has been shown to fine-tune and stabilize the regional structure and help maintain their functions in mRNA decoding, ribosome assembly, processing and translation.Pseudouridine in snRNA has been shown to enhance spliceosomal RNA-pre-mRNA interaction to facilitate splicing regulation.