0 11 Involvement involvement NN 12 14 of of IN 15 16 a a DT 17 23 second second JJ 24 41 lymphoid-specific lymphoid-specific JJ 42 50 enhancer enhancer NN 51 58 element element NN 59 61 in in IN 62 65 the the DT 66 76 regulation regulation NN 77 79 of of IN 80 94 immunoglobulin immunoglobulin NN 95 106 heavy-chain heavy-chain JJ 107 111 gene gene NN 112 122 expression expression NN 122 123 . . . 125 127 To to TO 128 137 determine determine VB 138 145 whether whether IN 146 154 enhancer enhancer NN 155 163 elements element NNS 164 166 in in IN 167 175 addition addition NN 176 178 to to TO 179 182 the the DT 183 189 highly highly RB 190 199 conserved conserve VBN 200 207 octamer octamer NN 208 209 ( ( ( 209 225 OCTA)-nucleotide octa)-nucleotide JJ 226 231 motif motif NN 232 235 are be VBP 236 245 important important JJ 246 249 for for IN 250 267 lymphoid-specific lymphoid-specific JJ 268 278 expression expression NN 279 281 of of IN 282 285 the the DT 286 300 immunoglobulin immunoglobulin NN 301 312 heavy-chain heavy-chain NN 313 314 ( ( ( 314 317 IgH IgH NNP 317 318 ) ) ) 319 323 gene gene NN 323 324 , , , 325 327 we we PRP 328 332 have have VBP 333 345 investigated investigate VBN 346 349 the the DT 350 356 effect effect NN 357 359 of of IN 360 368 mutating mutate VBG 369 372 the the DT 373 380 binding bind VBG 381 385 site site NN 386 389 for for IN 390 391 a a DT 392 400 putative putative JJ 401 411 additional additional JJ 412 429 lymphoid-specific lymphoid-specific JJ 430 443 transcription transcription NN 444 450 factor factor NN 450 451 , , , 452 462 designated designate VBN 463 472 NF-microB NF-microB NNP 472 473 , , , 474 476 in in IN 477 480 the the DT 481 487 murine murine JJ 488 491 IgH igh NN 492 500 enhancer enhancer NN 500 501 . . . 502 504 We we PRP 505 516 demonstrate demonstrate VBP 517 521 that that IN 522 525 the the DT 526 543 NF-microB-binding nf-microb-binding JJ 544 548 site site NN 549 554 plays play VBZ 555 556 a a DT 557 565 critical critical JJ 566 570 role role NN 571 573 in in IN 574 577 the the DT 578 581 IgH IgH NNP 582 590 enhancer enhancer NN 590 591 , , , 592 599 because because IN 600 608 mutation mutation NN 609 611 of of IN 612 615 the the DT 616 622 microB microb NN 623 626 DNA dna NN 627 632 motif motif NN 633 642 decreased decrease VBD 643 658 transcriptional transcriptional JJ 659 667 activity activity NN 668 670 of of IN 671 674 the the DT 675 678 IgH IgH NNP 679 687 enhancer enhancer NN 688 690 in in IN 691 696 cells cell NNS 697 699 of of IN 700 703 the the DT 704 710 B-cell b-cell NN 711 718 lineage lineage NN 719 722 but but CC 723 726 not not RB 727 729 in in IN 730 741 nonlymphoid nonlymphoid JJ 742 747 cells cell NNS 747 748 . . . 749 753 This this DT 754 760 effect effect NN 761 764 was be VBD 765 775 comparable comparable JJ 776 778 to to TO 779 781 or or CC 782 786 even even RB 787 795 stronger strong JJR 796 800 than than IN 801 804 the the DT 805 811 effect effect NN 812 814 of of IN 815 816 a a DT 817 825 mutation mutation NN 826 828 in in IN 829 832 the the DT 833 837 OCTA OCTA NNP 838 842 site site NN 842 843 . . . 844 852 Moreover moreover RB 852 853 , , , 854 862 combined combine VBN 863 871 mutation mutation NN 872 874 of of IN 875 879 both both CC 880 886 microB microB NNP 887 890 and and CC 891 895 OCTA OCTA NNP 896 901 sites site NNS 902 909 further further RBR 910 917 reduced reduce VBD 918 926 enhancer enhancer NN 927 935 activity activity NN 936 938 in in IN 939 947 lymphoid lymphoid JJ 948 953 cells cell NNS 953 954 . . . 955 968 Interestingly interestingly RB 968 969 , , , 970 980 alteration alteration NN 981 983 of of IN 984 990 either either CC 991 994 the the DT 995 1001 microB microb NN 1002 1004 or or CC 1005 1007 E3 e3 NN 1008 1012 site site NN 1013 1015 in in IN 1016 1017 a a DT 1018 1030 70-base-pair 70-base-pair JJ 1031 1039 fragment fragment NN 1040 1042 of of IN 1043 1046 the the DT 1047 1050 IgH IgH NNP 1051 1059 enhancer enhancer NN 1060 1064 that that WDT 1065 1070 lacks lack VBZ 1071 1074 the the DT 1075 1082 binding bind VBG 1083 1087 site site NN 1088 1091 for for IN 1092 1096 OCTA OCTA NNP 1097 1106 abolished abolish VBD 1107 1115 enhancer enhancer NN 1116 1124 activity activity NN 1125 1127 in in IN 1128 1136 lymphoid lymphoid JJ 1137 1142 cells cell NNS 1143 1153 completely completely RB 1153 1154 . . . 1155 1167 Nevertheless nevertheless RB 1167 1168 , , , 1169 1170 a a DT 1171 1179 multimer multimer NN 1180 1182 of of IN 1183 1186 the the DT 1187 1193 microB microb NN 1194 1199 motif motif NN 1200 1205 alone alone RB 1206 1212 showed show VBD 1213 1215 no no DT 1216 1224 enhancer enhancer NN 1225 1233 activity activity NN 1233 1234 . . . 1235 1240 DNase DNase NNP 1241 1253 footprinting footprinting NN 1254 1262 analysis analysis NN 1263 1275 corroborated corroborate VBD 1276 1279 the the DT 1280 1290 functional functional JJ 1291 1295 data datum NNS 1296 1303 showing show VBG 1304 1308 that that IN 1309 1310 a a DT 1311 1328 lymphoid-specific lymphoid-specific JJ 1329 1336 protein protein NN 1337 1342 binds bind VBZ 1343 1345 to to TO 1346 1349 the the DT 1350 1356 microB microb NN 1357 1360 DNA dna NN 1361 1366 motif motif NN 1366 1367 . . . 1368 1371 Our our PRP$ 1372 1379 results result NNS 1380 1387 suggest suggest VBP 1388 1392 that that IN 1393 1396 the the DT 1397 1403 microB microb NN 1404 1411 element element NN 1412 1414 is be VBZ 1415 1416 a a DT 1417 1420 new new JJ 1421 1428 crucial crucial JJ 1429 1436 element element NN 1437 1446 important important JJ 1447 1450 for for IN 1451 1468 lymphoid-specific lymphoid-specific JJ 1469 1479 expression expression NN 1480 1482 of of IN 1483 1486 the the DT 1487 1490 IgH IgH NNP 1491 1495 gene gene NN 1496 1499 but but CC 1500 1504 that that IN 1505 1516 interaction interaction NN 1517 1521 with with IN 1522 1529 another another DT 1530 1538 enhancer enhancer NN 1539 1546 element element NN 1547 1549 is be VBZ 1550 1559 essential essential JJ 1560 1563 for for IN 1564 1567 its its PRP$ 1568 1576 activity activity NN 1576 1577 . . .