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Cajal body

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Definition

noun

plural: Cajal bodies

(cell biology) A nuclear body involved in RNA processing (i.e. post-translational modification of small nuclear and small nucleolar RNAs), and in mammals, has a diameter ranging from 0.3 µm to 1.0 µm and coilin-positive


Details

Overview

In eukaryotic cell, the nucleus is the organelle responsible for maintaining the integrity of DNA and for controlling cellular activities such as metabolism, growth, and reproduction by regulating gene expression. It is a double-membraned organelle containing nuclear structures, e.g. chromatin and nuclear bodies. A nuclear body refers to any of the prominent non-membraned structures in the nucleus of the eukaryotic cell. Nuclear bodies are prominent structures of non-chromatinic fibrillary material and mostly proteinaceous. Examples of nuclear bodies are nucleolus, Cajal bodies and gems (Gemini of Cajal bodies), polymorphic interphase karyosomal association (PIKA) domains, promyelocytic leukaemia protein (PML) bodies, splicing speckles, paraspeckles, perichromatin fibrils, and clastosomes.


Characteristics

Cajal bodies (0.3–1.0 µm in diameter) are nuclear bodies that resemble balls of tangled thread. The nucleus could contain one to ten Cajal bodies.[1] It resembles another type of nuclear body, theGemini of Cajal bodies(also called gems). The latter derived its name from its semblance in size and shape of Cajal bodies, making them twins (Gemini). However, Gemini of Cajal bodies do not contain snRNPs (small nuclear ribonucleoproteins). Rather, they have SMN (survival of motor neuron) proteins. Furthermore, they are coilin-negative as opposed to Cajal bodies that are coilin-positive. The structure has dense foci of distribution of coilin. [2] Coilin is a protein structure and is one of the major components of Cajal bodies. It aids in the binding of the Cajal bodies to the nucleolus. Other proteins present in the Cajal bodies are snRNPs (small nuclear ribonucleoproteins) and snoRNPs (small nucleolar ribonucleoproteins). snRNP is a complex of RNA (particularly, small nuclear RNA or snRNA) and protein and is responsible for the recognition and removal of specific introns from the pre-mRNA. snoRNPs, in turn, is a complex of RNA and protein; the RNA constituent of snoRNP is the small nucleolar RNA or snoRNA. The snoRNPs are involved in the modification and processing of pre-rRNA in the nucleolus.


Biological functions

Cajal bodies are involved in RNA processing, e.g. in the maturation of snRNA and snoRNA, and in the modification of histone mRNA. Gemini of Cajal bodies assist the Cajal bodies in snRNP biogenesis. Post-transcriptional modification is a set of processes whereby the RNA primary transcript is modified after being transcribed in order to generate a mature and functional RNA molecule, and one of which is the splicing of introns.


Supplementary

Abbreviation(s)

  • CB

Synonym(s)

  • coiled body


Further reading

See also


Reference

  1. Pollard, T., Earnshaw, W., Schwartz, J. & Johnson, G. (2008). Cell biology. Philadelphia, PA: Saunders/Elsevier.
  2. Matera, A. G. & Frey, M. R. (August 1998). "Coiled bodies and gems: Janus or gemini?". American Journal of Human Genetics. 63 (2): 317–21. doi:10.1086/301992



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