[Identification of a snoRNA47 gene cluster in Oryza sativa]

Small nucleolar RNAs (snoRNAs) are required for ribose 2'-O-methylation of eukaryotic ribosomal RNA. By researching in international rice genome databases, a snoRNA gene cluster, consisting of three box C/D snoRNA gene candidates, was found on chromosome 6. All of snoRNA coding sequences in this cluster exhibited the characteristic structure of box C/D antisense snoRNA. They shared conserved box C and box D motifs, a stable terminal stem formed by a 4-6 nt-long inverted repetition sequence located upstream of box C and downstream of box D. All candidates had a 12 nt-long sequence complementary to the region from 621 nt to 6 32 nt in rice 18 S rRNA (nt numbering according to GenBank accession No. X00755), and might mediate the ribose 2'-O-methylation of A(623) in rice 18 S rRNA. Comparison of these sequences showed that these three rice snoRNAs were homologue of yeast snR47. These three rice snoRNAs were named as OSsnR47.1, OSsnR47.2 and OSsnR47.3, respectively. Primer extension assay showed that these three snoRNAs were transcribed in vivo and determined the 5' ends of each snoRNA. RT-PCR detected transcripts containing linked snoRNA47s and this suggested that the snoRNAs encoded in the cluster might be transcribed as a polycistronic transcript under the control of a single upstream promoter. The gene sequences encoding these three snoRNAs had been deposited in GenBank under accession number of AF453504 AF453503 an d AF453502.