MOLECULAR MECHANISMS INVOLVED IN RECEPTOR EDITING AT THE IG HEAVY-CHAIN LOCUS

In receptor editing, a phenomenon that has recently come to light and into favor, a rearranged VDJ or VJ gene segment encoding a variable re gion of an Ig chain is replaced by another. In this commentary, the mo lecular mechanisms involved in the editing process are examined in som e detail, Editing is most likely mediated by the same V(D)J recombinas e activity responsible for the formation of the original VDJ or VJ seg ment. An embedded heptamer, which is present near the 3' end of many V -H elements, is used as the recombination signal sequence at the Ig he avy chain locus, It has been postulated that the mediation of receptor editing is the evolutionary force maintaining the embedded heptamer. Some of the evidence for and against this hypothesis is discussed.