Figure 4.
The 22-nt motif associated with the phased 21-mer clusters. (A) The phased and unphased small RNAs comprising a representative 21-mer cluster are shown. The location of the motif is shown by the arrow at the top, below “motif.” The polarity of the small RNAs is indicated by the arrows, and the number of times the small RNA was sequenced is indicated above the arrow. This 21-mer cluster is located at chr1:34554118..34554411. The probability that this cluster is phased by chance alone is 2.6 × 10−17, and the probability that the indicated motif matches the consensus by chance alone is 2.4 × 10−8. (B) The approximate probability of a nucleotide occurring at specific positions of the motif is shown in the top matrix, and the consensus sequence of the motif is shown below the matrix. (C) The positions of the 705 motifs that are offset 12 nt from the phase of the 21-mer clusters are shown.