Homo sapiens U105B snoRNA. This C/D box snoRNA was characterized by Yang et al. (2006) using the snoSeeker software. Its expression was not experimentally demonstrated. Both U105 and U105B reside in the same host gene (PPAN), and are predicted to guide the 2’O-ribose methylation of 18S rRNA U799. They probably result from an ancient intragenic duplication. Whereas the rRNA anti-sense sequence of SNORD105 is highly conserved from human to fishes, the anti-sense sequence of U105B is partially deleted in several species including rhesus monkey. In tetraodon, fugu, stickleback and medaka, the PPAN gene contains a third paralog, U105C, with a 2bp insertion between the rRNA anti-sense sequence and the D box, possibly shifting upstream by 2 bases the methylation target.