T cell receptor DJ but not VDJ rearrangement within a recombination substrate introduced into a pre-B cell line

To elucidate mechanisms that regulate ordered and tissue-specific assembly of Ig and TCR variable region gene segments, we have Introduced a recombination substrate comprised of germline TCR beta V, D, and J gene segments Into an Abelson murine leukemia virus-transformed pre-B cell line that actively rearranges endogenous Ig H chain variable region gene segments but does not rearrange endogenous light chain or TCR variable region gene segments. We find that these cells efficiently Join D beta segments to J beta segments within the mini-locus, but that they do not make any detectable site-specific rearrangements of the Introduced V beta segment even though It is closely linked in the same construct to the D beta. These findings suggest that factors necessary for V beta to (D beta)J beta Joining may be absent in these pre-B cells and also Imply that the order in which TCR V beta, D beta, and J beta segments are rearranged can be influenced by factors other than the 12/23 recombination rule. Furthermore, In agreement with the an accessibility model of VDJ recombinase control, the D beta region of the construct was found to be relatively more sensitive to DNAase I digestion in isolated nuclei when compared to the unrearranged V beta region.