Homo sapiens C/D box snoRNA U57. This snoRNA was cloned from HeLa cells by Kiss-Laszlo et al. (1996). It is predicted to guide the 2'O-ribose methylation of 18S rRNA A99. The C/D box snoRNAs U57, U56, U86 and HBII-55, and the H/ACA box snoRNA ACA51 share the same host gene (NOL5A). This gene encodes the Nucleolar Protein 5A (also known as NOP56), one of the four core proteins of C/D box snRNPs.