The T cell receptor β enhancer promotes access and pairing of Dβ and Jβ gene segments during V(D)J recombination

Abstract

The precise function of cis elements in regulating V(D)J recombination is still controversial. Here, we determined the effect of inactivation of the TCRβ enhancer (Eβ) on cleavage and rearrangement of Dβ1, Dβ2, Jβ1, and Jβ2 gene segments in CD4-CD8 - [double-negative (DN)] and CD4+CD8+ [double-positive (DP)] thymocytes. In Eβ-deficient mice, (i) Dβ1 rearrangements were more severely impaired than Dβ2 rearrangements; (ii) most of the Dβ and Jβ cleavages and rearrangements occurred in DP, rather than in DN, thymocytes; and (iii) most of the 3′ Dβ1 cleavages were coupled to 5′ Dβ2 cleavages instead of to Jβ cleavages, resulting in nonstandard Dβ1-Dβ2-Jβ2 joints. These findings suggest that the Eβ regulates TCRβ rearrangement by promoting accessibility of Dβ and Jβ gene segments in DN thymocytes and proper pairing between Dβ1 and Jβ gene segments for cleavage and joining in DP thymocytes.