title: T cell receptor (TCR) alpha/delta locus enhancer identity and position are critical for the assembly of TCR delta and alpha variable region genes.
abstract: T cell receptor (TCR) delta and alpha variable region genes are assembled from germ-line gene segments located in a single chromosomal locus in which TCR delta segments are situated between TCR alpha segments. The TCR alpha enhancer (E alpha) located at the 3' end of the TCR alpha/delta locus functions over a long chromosomal distance to promote TCR alpha rearrangement and maximal TCR delta expression; whereas the TCR delta enhancer (E delta) is located among the TCR delta segments and functions with additional element(s) to mediate TCR delta rearrangement. We used gene-targeted mutation to evaluate whether the identity of E alpha and the position of E delta are critical for the developmental stage-specific assembly of TCR delta and alpha variable region genes. Specific replacement of E alpha with E delta, the core E alpha element (E alpha C), or the Ig heavy chain intronic enhancer (iE mu), all of which promote accessibility in the context of transgenic V(D)J recombination substrates, did not promote a significant level of TCR alpha rearrangement beyond that observed in the absence of E alpha. Therefore, the identity and full complement of E alpha-binding sites are critical for promoting accessibility within the TCR alpha locus. In the absence of the endogenous E delta element, specific replacement of E alpha with E delta also did not promote TCR delta rearrangement. However, deletion of intervening TCR alpha/delta locus sequences to restore the inserted E delta to its normal chromosomal position relative to 5' sequences rescued TCR delta rearrangement. Therefore, unlike E alpha, E delta lacks ability to function over the large intervening TCR alpha locus and or E delta function requires proximity to additional upstream element(s) to promote TCR delta accessibility.
authors.affiliation: Howard Hughes Medical Institute, Children's Hospital, Harvard Medical School and Center for Blood Research, Boston, MA 02115, USA.
authors.forename: Craig H
authors.initials: CH
authors.lastname: Bassing
authors.forename: Robert E
authors.initials: RE
authors.lastname: Tillman
authors.forename: Barbara B
authors.initials: BB
authors.lastname: Woodman
authors.forename: David
authors.initials: D
authors.lastname: Canty
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Monroe
authors.forename: Barry P
authors.initials: BP
authors.lastname: Sleckman
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Alt
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D015704:CD4 Antigens / Q000096:biosynthesis; D016827:CD8 Antigens / Q000096:biosynthesis; D004742:Enhancer Elements, Genetic; D005434:Flow Cytometry; D015321:Gene Rearrangement; D019673:Genes, T-Cell Receptor alpha / Q000502:physiology*; D019676:Genes, T-Cell Receptor delta / Q000502:physiology*; D006720:Homozygote; D006825:Hybridomas / Q000378:metabolism; D008214:Lymphocytes / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens