Nuclear Matrix Bound V(D)J Recombination Activity in Rat Thymus Nuclei: An in Vitro System

We report here that a high level of V(D)J recombination activity is tightly associated with high-salt-resistant nuclear matrix isolated from thymus glands from 2- to 3-week-old rats. The soluble nuclear fractions either were devoid of or contained a very low level of recombinase activity. This is the first time that the process mimicking V(D)J recombination has been achieved in an in vitro system. The matrix-bound V(D)J recombinase activity was further found to be lymphoid specific, detectable only during early stages of development. These observations suggest that in vitro recombination of V(D)J segments of genes encoding antigen-binding proteins could be a matrix-bound process and that the nuclear matrix may be an important intranuclear domain for the functional organization of the V(D)J recombinase system.