Figure 4: Regulation of transcription of the rearranged Tcrd and Tcra genes by distant enhancers in γδ and αβ T lymphocytes, respectively. The V, D, and J gene segments are represented by black narrow rectangles. The Cδ and Cα regions are represented by black large rectangles. Red lines indicate the areas occupied by Trav/Trdv and Traj gene segments. The rearranged Tcrd VDJ and Tcra VJ transcripts are written in bold blue characters. The position of the functionally relevant described regulatory elements is indicated as follows: Eδ as a blue circle, TEAp as a purple circle, E3´-Jα as an orange circle, LCR as a pink line, Eα as a red circle, HS-1´as a black rectangle, and HS2-6 as brown ovals. Curved arrows represent the predicted enhancer-promoter interactions based on the functional experiments [34,43,62]. In γδ T lymphocytes, Eα, and also presumably Eδ, functionally interact with the rearranged Trav/Trdv promoter. The black arrow represents the functionally relevant interaction between Eα and the rearranged Trav/Trdv promoter in comparison to the presumed interaction between Eδ and the rearranged Trav/Trdv promoter, which is represented in grey. In αβ T lymphocytes, Eα is strongly inhibited and its contribution to the transcription of the rearranged Tcra locus is uncertain. The contribution of the recently described E3´-Jα enhancer to the transcription of the rearranged Tcra locus is also unknown. The putatively weak or uncertain interactions between these enhancers and the rearranged Trav/Trdv promoters are represented as dashed light lines.