Makarova Julia A, Kramerov Dmitri A
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilov St., Moscow 119991, Russia.
Genomics. 2009 Jul;94(1):11-9. doi: 10.1016/j.ygeno.2009.02.003. Epub 2009 Mar 9.
C/D box small nucleolar RNAs (snoRNAs) guide site-specific 2'-O-methylation of RNAs. Nearly all C/D box snoRNAs with known targets are involved in rRNA modification. In vertebrates, snoRNAs are encoded in introns of various genes and their processing is coupled with splicing of host gene pre-mRNA. Here, the genes encoding C/D box snoRNAs that guide 2'-O-methylation of rRNA were identified and analyzed in vertebrate genomes. The number of copies of most C/D box snoRNA genes proved to be lower in placental mammals compared to other vertebrates. This can be due to smaller oocytes and accordingly lower number of ribosomes in them in eutherians. The targets of snoRNAs encoded by single-copy and multiple-copy genes proved to have different distribution in rRNAs. The causes of this difference are discussed. In some cases, the transcripts of homologous C/D box RNA genes were shown to guide the modification of neighboring nucleotides in rRNA. C/D box snoRNA pseudogenes were found in all vertebrate classes. Three novel C/D box snoRNAs were found in Xenopus tropicalis that may guide 2'-O-methylation of Xenopus-specific rRNA sites. A list of 922 annotated C/D box snoRNA genes is presented.
C/D盒小核仁RNA（snoRNAs）指导RNA的位点特异性2'-O-甲基化。几乎所有已知靶标的C/D盒snoRNAs都参与核糖体RNA（rRNA）修饰。在脊椎动物中，snoRNAs编码于各种基因的内含子中，其加工与宿主基因前体mRNA的剪接偶联。在此，在脊椎动物基因组中鉴定并分析了编码指导rRNA 2'-O-甲基化的C/D盒snoRNAs的基因。与其他脊椎动物相比，胎盘哺乳动物中大多数C/D盒snoRNA基因的拷贝数较低。这可能是由于真兽类动物的卵母细胞较小，因此其中的核糖体数量也较少。单拷贝和多拷贝基因编码的snoRNAs的靶标在rRNAs中具有不同的分布。讨论了这种差异的原因。在某些情况下，同源C/D盒RNA基因的转录本被证明可指导rRNA中相邻核苷酸的修饰。在所有脊椎动物类别中均发现了C/D盒snoRNA假基因。在热带爪蟾中发现了三种新型C/D盒snoRNAs，它们可能指导爪蟾特异性rRNA位点的2'-O-甲基化。列出了922个注释的C/D盒snoRNA基因。
