Content and conservation properties of each sequenced fraction. a) The count of small RNAs mapping to specific types of annotation is shown as histograms for the short and long libraries. Classifications are based on the process described in Fig 2 and Methods. b) The mean PhastCons  scores for the region -300 to +300 relative to the midpoint of each small RNA cluster are shown, broken up into two fractions. Position 0 indicates the midpoint of each cluster. For comparison, 500 equally sized randomly selected regions where the midpoint was either exonic, intronic, or intergenic was analyzed in the same way. The small fraction is generally highly conserved, which is expected due to many potential miRNA sequences it contains. The longer fraction is on average less conserved than exonic sequences, but considerably higher conserved than intergenic or intronic regions.
Kawaji et al. BMC Genomics 2008 9:157 doi:10.1186/1471-2164-9-157