Messenger RNA editing

Fitzgerald LW, Iyer G, Conklin DS, et al. Messenger RNA editing of the human serotonin 5-HT2C receptor. Neuropsychopharmacology 1999 21 82S-90S. 

Cattaneo R. (1991) Different types of messenger RNA editing. Annu. Rev. Genet. 25 71. 

Teng, B., Burant, C. F., and Davidson, N. O. (1993). Molecular cloning of an apolipo-protein B messenger RNA editing protein. Science 260, 1816-1819. 

Wedekind, J. E., Dance, G. S., Sowden, M. P., and Smith, H. C. (2003). Messenger RNA editing in mammals New members of the APOBEC family seeking roles in the family business, [erratum appears in Trends Genet. 2003 Jul 19(7) 369]. Trends Genet. 19, 207-216. 

The total number of proteins found in nature is extremely large. The 1992 edition of the Enzyme List (Webb, 1992) lists 3196 enzymes. The total number of proteins in a eukaryotic cell has been estimated to be between 10,000 and 20,000 (Alberts et al., 1989), based upon the number of different messenger RNAs in a typical eukaryotic cell. This number does not reflect the thousands of natural mutants of any one protein that may occur. (Approximately 500 naturally occurring mutants of human hemoglobin have been identified to date.) Nor does it take into account the fact that there are often very substantial differences in homologous proteins that perform the same function in different species. A minimal estimate of the number of different proteins in living systems on earth would be on the order of 10,000 x 500 X the number of species i.e., literally, billions. 

RNA editing is a term used to describe the structural alteration, insertion, or deletion of nucleotides in RNA that changes its coding properties. When the modification occurs in messenger RNA (mRNA), it can result in the translation of a protein sequence different from that predicted by the DNA sequence of the gene. Thus, this process plays an important role in creating functional diversity in the protein products of gene expression. 

Messenger RNA (mRNA) is synthesized in the nucleus, as a copy of one strand of DNA (the process of transcription section 9-2.2.1). After some editing of the message, it is transferred into the cytosol, where it binds to ribosomes. The information carried by the mRNA is then translated into the amino acid sequence of the protein. 

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