The Cajal body: a meeting place for spliceosomal snRNPs in the nuclear maze

Chromosoma. 2006 Oct;115(5):343-54. doi: 10.1007/s00412-006-0056-6. Epub 2006 Mar 31.

Abstract

Spliceosomal small nuclear ribonucleoprotein particles (snRNPs) are essential pre-mRNA splicing factors that consist of small nuclear RNAs (snRNAs) complexed with specific sets of proteins. A considerable body of evidence has established that snRNP assembly is accomplished after snRNA synthesis in the nucleus through a series of steps involving cytoplasmic and nuclear phases. Recent work indicates that snRNPs transiently localize to the Cajal body (CB), a nonmembrane-bound inclusion present in the nuclei of most cells, for the final steps in snRNP maturation, including snRNA base modification, U4/U6 snRNA annealing, and snRNA-protein assembly. Here, we review these findings that suggest a crucial role for CBs in the spliceosome cycle in which production of new snRNPs--and perhaps regenerated snRNPs after splicing--is promoted by the concentration of substrates in this previously mysterious subnuclear organelle. These insights allow us to speculate on the role of nuclear bodies in regulating the dynamics of RNP assembly to maintain a functional pool of factors available for key steps in gene expression.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Coiled Bodies / genetics
  • Coiled Bodies / metabolism*
  • Histones / genetics
  • Histones / metabolism
  • Humans
  • Models, Biological
  • Nuclear Proteins / deficiency
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA Splicing
  • RNA, Small Nuclear / chemistry
  • RNA, Small Nuclear / genetics
  • RNA, Small Nuclear / metabolism
  • Ribonucleoproteins, Small Nuclear / chemistry
  • Ribonucleoproteins, Small Nuclear / genetics
  • Ribonucleoproteins, Small Nuclear / metabolism*
  • Spliceosomes / genetics
  • Spliceosomes / metabolism*

Substances

  • Histones
  • Nuclear Proteins
  • RNA, Small Nuclear
  • Ribonucleoproteins, Small Nuclear
  • p80-coilin