Homo sapiens C/D box U8 snoRNA. U8 was initially sequenced from Novikoff hepatoma cells after immunoprecipitation with anti-Sm antibodies (Reddy et al., 1985). The human U8 was sequenced by Tyc and Steitz (1989) after immunoprecipatation with anti-fibrillarin and anti-TMG antibodies. U8 snRNA is transcribed from an independent transcriptional unit by RNA polII and possess an m227G trimethylguanosine cap. In addition to the four C/D snoRNP proteins, Xenopus U8 snoRNA binds LSm (like Sm) proteins at the conserved motive GCUGAUUA (nts 78-85 in the human sequence). Xenopus U8 snoRNA also binds a nucleolar protein , X29, that displays decapping activity on U8 m227G cap, and may be a negative regulator of U8 snoRNA in vivo (Gosh et al., 2004). A potential human orthologue of X29 may be the hypothetical protein FLJ31265.
The disruption of U8 RNA in Xenopus oocytes showed that U8 snRNP is essential for correct maturation of the 5.8S and 28S rRNAs at both their 5' and 3' ends (Peculis and Steitz, 1993). The 5' most 15 nts of U8 are essential for U8snRNP functionning. These 15 nucleotides have the potential to base pair with the 5' end of 28S rRNA in a region where, in the mature ribosome, the 5' end of 28S interacts with the 3' end of 5.8S. An U8 mutant with increased complementarity with 28S rRNA is not functional in vivo, consistent with the notion that U8 must be displaced from pre-28S rRNA by 5.8S rRNA for processing to occur (Peculis, 1997).
GenBank accession number :
Host gene : Independent transcriptional unit(s)
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