0 1 A a DT 2 7 novel novel JJ 8 9 B B NNP 10 22 cell-derived cell-derived JJ 23 34 coactivator coactivator NN 35 46 potentiates potentiate VBZ 47 50 the the DT 51 61 activation activation NN 62 64 of of IN 65 79 immunoglobulin immunoglobulin NN 80 89 promoters promoter NNS 90 92 by by IN 93 108 octamer-binding octamer-binding JJ 109 122 transcription transcription NN 123 130 factors factor NNS 130 131 . . . 133 134 A a DT 135 140 novel novel JJ 141 142 B B NNP 143 158 cell-restricted cell-restricted JJ 159 167 activity activity NN 167 168 , , , 169 177 required require VBN 178 181 for for IN 182 186 high high JJ 187 193 levels level NNS 194 196 of of IN 197 218 octamer/Oct-dependent octamer/oct-dependent JJ 219 232 transcription transcription NN 233 237 from from IN 238 240 an an DT 241 255 immunoglobulin immunoglobulin NN 256 261 heavy heavy JJ 262 267 chain chain NN 268 269 ( ( ( 269 272 IgH IgH NNP 272 273 ) ) ) 274 282 promoter promoter NN 282 283 , , , 284 287 was be VBD 288 296 detected detect VBN 297 299 in in IN 300 302 an an DT 303 305 in in FW 306 311 vitro vitro FW 312 318 system system NN 319 329 consisting consist VBG 330 332 of of IN 333 337 HeLa HeLa NNP 338 350 cell-derived cell-derived JJ 351 359 extracts extract NNS 360 372 complemented complement VBN 373 377 with with IN 378 390 fractionated fractionate VBN 391 392 B B NNP 393 397 cell cell NN 398 405 nuclear nuclear JJ 406 414 proteins protein NNS 414 415 . . . 416 419 The the DT 420 426 factor factor NN 427 438 responsible responsible JJ 439 442 for for IN 443 447 this this DT 448 456 activity activity NN 457 460 was be VBD 461 471 designated designate VBN 472 475 Oct Oct NNP 476 487 coactivator coactivator NN 488 492 from from IN 493 494 B B NNP 495 500 cells cell NNS 501 502 ( ( ( 502 507 OCA-B OCA-B NNP 507 508 ) ) ) 508 509 . . . 510 515 OCA-B OCA-B NNP 516 526 stimulates stimulate VBZ 527 530 the the DT 531 544 transcription transcription NN 545 549 from from IN 550 552 an an DT 553 556 IgH IgH NNP 557 565 promoter promoter NN 566 568 in in IN 569 580 conjunction conjunction NN 581 585 with with IN 586 592 either either CC 593 598 Oct-1 oct-1 NN 599 601 or or CC 602 607 Oct-2 oct-2 NN 608 611 but but CC 612 617 shows show VBZ 618 620 no no DT 621 632 significant significant JJ 633 639 effect effect NN 640 642 on on IN 643 646 the the DT 647 668 octamer/Oct-dependent octamer/oct-dependent JJ 669 682 transcription transcription NN 683 685 of of IN 686 689 the the DT 690 702 ubiquitously ubiquitously RB 703 712 expressed express VBN 713 720 histone histone NN 721 724 H2B h2b NN 725 733 promoter promoter NN 734 737 and and CC 738 741 the the DT 742 755 transcription transcription NN 756 758 of of IN 759 763 USF- usf- NN 764 767 and and CC 768 781 Sp1-regulated sp1-regulated JJ 782 791 promoters promoter NNS 791 792 . . . 793 798 Taken take VBN 799 807 together together RB 807 808 , , , 809 812 our our PRP$ 813 820 results result NNS 821 828 suggest suggest VBP 829 833 that that IN 834 839 OCA-B oca-b NN 840 842 is be VBZ 843 844 a a DT 845 852 tissue- tissue- NN 852 853 , , , 854 863 promoter- promoter- NN 863 864 , , , 865 868 and and CC 869 884 factor-specific factor-specific JJ 885 896 coactivator coactivator NN 897 900 and and CC 901 905 that that IN 906 911 OCA-B oca-b NN 912 915 may may MD 916 918 be be VB 919 920 a a DT 921 926 major major JJ 927 938 determinant determinant NN 939 942 for for IN 943 944 B B NNP 945 958 cell-specific cell-specific JJ 959 969 activation activation NN 970 972 of of IN 973 987 immunoglobulin immunoglobulin NN 988 997 promoters promoter NNS 997 998 . . . 999 1001 In in IN 1002 1007 light light NN 1008 1010 of of IN 1011 1014 the the DT 1015 1023 evidence evidence NN 1024 1031 showing show VBG 1032 1040 physical physical JJ 1041 1044 and and CC 1045 1055 functional functional JJ 1056 1068 interactions interaction NNS 1069 1076 between between IN 1077 1080 Oct Oct NNP 1081 1088 factors factor NNS 1089 1092 and and CC 1093 1098 OCA-B oca-b NN 1098 1099 , , , 1100 1102 we we PRP 1103 1110 propose propose VBP 1111 1112 a a DT 1113 1122 mechanism mechanism NN 1123 1125 of of IN 1126 1132 action action NN 1133 1136 for for IN 1137 1142 OCA-B OCA-B NNP 1143 1146 and and CC 1147 1154 discuss discuss VBP 1155 1158 the the DT 1159 1171 implications implication NNS 1172 1174 of of IN 1175 1180 OCA-B oca-b NN 1181 1184 for for IN 1185 1188 the the DT 1189 1204 transcriptional transcriptional JJ 1205 1215 regulation regulation NN 1216 1218 of of IN 1219 1224 other other JJ 1225 1240 tissue-specific tissue-specific JJ 1241 1250 promoters promoter NNS 1250 1251 . . .