snoRNA (small nucleolar RNA) is a small RNA of 60-300 nucleotides in length, containing a family of nuclear RNAs present in all eukaryotic cells. snoRNAs are concentrated in the nucleolus, and most serve as guide RNA for post-transcriptional modification of ribosomal RNA and some spliceosomal RNAs. The post-transcriptional modification are important for the production of efficient and accurate ribosomes. And others are involved in nuclear lysis of the original rRNA transcript.