0 2 An an DT 3 20 enhancer-blocking enhancer-blocking JJ 21 28 element element NN 29 36 between between IN 37 42 alpha alpha NN 43 46 and and CC 47 52 delta delta NN 53 57 gene gene NN 58 66 segments segment NNS 67 73 within within IN 74 77 the the DT 78 83 human human JJ 84 85 T t NN 86 90 cell cell NN 91 99 receptor receptor NN 100 111 alpha/delta alpha/delta NN 112 117 locus locus NN 117 118 . . . 120 121 T t NN 122 126 cell cell NN 127 135 receptor receptor NN 136 137 ( ( ( 137 140 TCR TCR NNP 140 141 ) ) ) 142 147 alpha alpha NN 148 151 and and CC 152 157 delta delta NN 158 162 gene gene NN 163 171 segments segment NNS 172 175 are be VBP 176 185 organized organize VBN 186 192 within within IN 193 194 a a DT 195 201 single single JJ 202 209 genetic genetic JJ 210 215 locus locus NN 216 219 but but CC 220 223 are be VBP 224 238 differentially differentially RB 239 248 regulated regulate VBN 249 255 during during IN 256 257 T t NN 258 262 cell cell NN 263 274 development development NN 274 275 . . . 276 278 An an DT 279 296 enhancer-blocking enhancer-blocking JJ 297 304 element element NN 305 306 ( ( ( 306 312 BEAD-1 BEAD-1 NNP 312 313 , , , 314 317 for for IN 318 326 blocking block VBG 327 334 element element NN 335 346 alpha/delta alpha/delta NN 347 348 1 1 CD 348 349 ) ) ) 350 353 was be VBD 354 363 localized localized JJ 364 366 to to TO 367 368 a a DT 369 375 2.0-kb 2.0-kb JJ 376 382 region region NN 383 384 3 3 CD 384 385 ’ ' SYM 386 388 of of IN 389 392 TCR TCR NNP 393 398 delta delta NN 399 403 gene gene NN 404 412 segments segment NNS 413 416 and and CC 417 418 5 5 CD 418 419 ’ ' SYM 420 422 of of IN 423 426 TCR TCR NNP 427 432 alpha alpha NN 433 440 joining joining NN 441 445 gene gene NN 446 454 segments segment NNS 455 461 within within IN 462 466 this this DT 467 472 locus locus NN 472 473 . . . 474 480 BEAD-1 BEAD-1 NNP 481 488 blocked block VBD 489 492 the the DT 493 500 ability ability NN 501 503 of of IN 504 507 the the DT 508 511 TCR TCR NNP 512 517 delta delta NN 518 526 enhancer enhancer NN 527 528 ( ( ( 528 534 Edelta Edelta NNP 534 535 ) ) ) 536 538 to to TO 539 547 activate activate VB 548 549 a a DT 550 558 promoter promoter NN 559 563 when when WRB 564 571 located located JJ 572 579 between between IN 580 583 the the DT 584 587 two two CD 588 590 in in IN 591 592 a a DT 593 613 chromatin-integrated chromatin-integrated JJ 614 623 construct construct NN 623 624 . . . 625 627 We we PRP 628 635 propose propose VBP 636 640 that that IN 641 647 BEAD-1 bead-1 NN 648 657 functions function VBZ 658 660 as as IN 661 662 a a DT 663 671 boundary boundary NN 672 676 that that WDT 677 686 separates separate VBZ 687 690 the the DT 691 694 TCR TCR NNP 695 706 alpha/delta alpha/delta NN 707 712 locus locus NN 713 717 into into IN 718 726 distinct distinct JJ 727 737 regulatory regulatory JJ 738 745 domains domain NNS 746 756 controlled control VBN 757 759 by by IN 760 766 Edelta Edelta NNP 767 770 and and CC 771 774 the the DT 775 778 TCR TCR NNP 779 784 alpha alpha NN 785 793 enhancer enhancer NN 793 794 , , , 795 798 and and CC 799 803 that that IN 804 806 it it PRP 807 815 prevents prevent VBZ 816 822 Edelta Edelta NNP 823 827 from from IN 828 835 opening open VBG 836 839 the the DT 840 849 chromatin chromatin NN 850 852 of of IN 853 856 the the DT 857 860 TCR TCR NNP 861 866 alpha alpha NN 867 874 joining joining NN 875 879 gene gene NN 880 888 segments segment NNS 889 892 for for IN 893 896 VDJ VDJ NNP 897 910 recombination recombination NN 911 913 at at IN 914 916 an an DT 917 922 early early JJ 923 928 stage stage NN 929 931 of of IN 932 933 T t NN 934 938 cell cell NN 939 950 development development NN 950 951 . . .