Recombination Signal Sequences
Encyclopedia
The regional genes used to generate T-cell receptors
T cell receptor
The T cell receptor or TCR is a molecule found on the surface of T lymphocytes that is responsible for recognizing antigens bound to major histocompatibility complex molecules...

 and Immunoglobulin molecules
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

, are flanked by Recombination Signal Sequences (RSSs) that are recognized by a group of enzymes known collectively as the VDJ recombinase. RSSs are composed of seven conserved nucleotides (a heptamer) that reside next to the gene encoding sequence followed by a spacer (containing either 12 or 23 unconserved nucleotides) followed by a conserved nonamer (9 base pairs). The RSSs are present on the 3’ side
Directionality (molecular biology)
Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. The chemical convention of naming carbon atoms in the nucleotide sugar-ring numerically gives rise to a 5′-end and a 3′-end...

 (downstream) of a V region and the 5’
Directionality (molecular biology)
Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. The chemical convention of naming carbon atoms in the nucleotide sugar-ring numerically gives rise to a 5′-end and a 3′-end...

 side (upstream) of the J region. These are the sides that will be involved in the joining. Only a pair of dissimilar spacer RSSs are efficiently recombined
Genetic recombination
Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...

(i.e. one with a spacer of 12 nucleotides will be recombined with one that has a spacer containing 23 nucleotides). This is known as the 12/23 rule of recombination (or the one-turn/two-turn rule).
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK