Allelic exclusion is a process in which only one allele of a gene is expressed in a diploid cell, while expression of another allele is suppressed .
There are two different mechanisms of allelic exclusion. In the first case, the gene allele can be suppressed at the stage of transcription , which leads to the expression of only the second allele. In the second case, both alleles can be transcribed, but post-transcriptional and post - translational mechanisms lead to the elimination of the product of one of the alleles.
Allelic exclusion mechanisms are not fully understood. [one]
Allelic exclusion in B cells
Allelic exclusion is most often found in genes encoding surface cell receptors , and has been studied in most detail for cells of the immune system - B-lymphocytes. [2] Upon the maturation of B-lymphocytes, successful V (D) J recombination of the gene encoding the immunoglobulin heavy chain on one chromosome leads to the fact that in the other chromosome V (D) J, rearrangement is blocked. In case of unsuccessful rearrangement in one chromosome, rearrangement in the homologous chromosome occurs. If gene rearrangement in both chromosomes does not end in success, the cell dies.
As a result of allelic exclusion, all antigenic receptors of one lymphocyte have the same amino acid sequence in the variable domains of heavy chains. Since the specificity of the antigen binding site is determined by both the variable region of the heavy chain and the variable region of the light chain encoded at the corresponding locus of the genome, B-lymphocytes having the same recombination products of heavy chains will most likely differ due to differences in the genes of the light chains.
Notes
- ↑ Mostoslavsky R., Alt FW, Rajewsky K. The lingering enigma of the allelic exclusion mechanism (English) // Cell : journal. - Cell Press 2004. - Vol. 118 , no. 5 . - P. 539-544 . - DOI : 10.1016 / j.cell.2004.08.0.023 . - PMID 15339659 .
- ↑ Chess A. Expansion of the allelic exclusion principle? (English) // Science. - 1998. - Vol. 279 , no. 5359 . - P. 2067-2068 . - DOI : 10.1126 / science.279.5359.2067 . - PMID 9537917 .
Literature
- Cellular and Molecular Immunology (5th Ed.) Abbas AK, and Lichtman AH., Editor: Saunders, Philadelphia, 2003.