Cotranscriptional recognition of human intronic box H/ACA snoRNAs occurs in a splicing-independent manner

Mol Cell Biol. 2006 Apr;26(7):2540-9. doi: 10.1128/MCB.26.7.2540-2549.2006.


Processing from pre-mRNA introns is a widespread mechanism to generate human box C/D and H/ACA snoRNAs. Recent studies revealed that an optimal position relative to the 3' splice site is important for efficient processing of most box C/D snoRNAs and that assembly of box C/D snoRNPs is stimulated by splicing factors likely bound to the branch point region. Here we have investigated the processing of another major class of human intron-encoded RNAs, the box H/ACA snoRNAs. Analysis of 80 H/ACA RNA genes revealed that human H/ACA RNAs possess no preferential localization close to the 3' or 5' splice site. In vivo processing experiments confirmed that H/ACA intronic snoRNAs are processed in a position-independent manner, indicating that there is no synergy between H/ACA RNA processing and splicing. We also showed that recognition of intronic H/ACA snoRNAs and assembly of pre-snoRNPs is an early event that occurs during transcription elongation parallel with pre-mRNA splice site selection. Finally, we found that efficient processing and correct nucleolar localization of the human U64 H/ACA snoRNA requires RNA polymerase II-mediated synthesis of the U64 precursor. This suggests that polymerase II-associated factors direct the efficient assembly and determine the correct subnuclear trafficking of human H/ACA snoRNPs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / metabolism
  • DNA Polymerase II / metabolism
  • DNA, Intergenic / genetics
  • Globins / genetics
  • Humans
  • Introns / genetics*
  • Nuclear Proteins / metabolism
  • RNA Precursors / genetics
  • RNA Processing, Post-Transcriptional / genetics
  • RNA Splice Sites / genetics
  • RNA Splicing / genetics
  • RNA, Small Nucleolar / genetics*
  • RNA-Binding Proteins / metabolism
  • Transcription, Genetic / genetics*


  • Cell Cycle Proteins
  • DKC1 protein, human
  • DNA, Intergenic
  • Nuclear Proteins
  • RNA Precursors
  • RNA Splice Sites
  • RNA, Small Nucleolar
  • RNA-Binding Proteins
  • Globins
  • DNA Polymerase II