0 5 OBF-1 OBF-1 NNP 5 6 , , , 7 8 a a DT 9 14 novel novel JJ 15 16 B B NNP 17 30 cell-specific cell-specific JJ 31 42 coactivator coactivator NN 43 47 that that WDT 48 58 stimulates stimulate VBZ 59 73 immunoglobulin immunoglobulin NN 74 82 promoter promoter NN 83 91 activity activity NN 92 99 through through IN 100 111 association association NN 112 116 with with IN 117 132 octamer-binding octamer-binding JJ 133 141 proteins protein NNS 141 142 . . . 144 150 Recent recent JJ 151 162 biochemical biochemical JJ 163 166 and and CC 167 174 genetic genetic JJ 175 182 studies study NNS 183 191 indicate indicate VBP 192 196 that that IN 197 199 in in IN 200 208 addition addition NN 209 211 to to TO 212 215 the the DT 216 231 octamer-binding octamer-binding JJ 232 240 proteins protein NNS 241 246 Oct-1 oct-1 NN 247 250 and and CC 251 256 Oct-2 oct-2 NN 256 257 , , , 258 263 other other JJ 264 265 B B NNP 266 270 cell cell NN 271 281 components component NNS 282 285 are be VBP 286 294 required require VBN 295 298 for for IN 299 318 lymphoid-restricted lymphoid-restricted JJ 318 319 , , , 320 327 octamer octamer NN 328 341 site-mediated site-mediated JJ 342 356 immunoglobulin immunoglobulin NN 357 361 gene gene NN 362 370 promoter promoter NN 371 379 activity activity NN 379 380 . . . 381 386 Using use VBG 387 388 a a DT 389 396 genetic genetic JJ 397 403 screen screen NN 404 406 in in IN 407 412 yeast yeast NN 412 413 , , , 414 416 we we PRP 417 421 have have VBP 422 430 isolated isolate VBN 431 432 B B NNP 433 445 cell-derived cell-derived JJ 446 451 cDNAs cdna NNS 452 460 encoding encode VBG 461 472 Oct-binding oct-binding JJ 473 479 factor factor NN 480 481 1 1 CD 482 483 ( ( ( 483 488 OBF-1 obf-1 NN 488 489 ) ) ) 489 490 , , , 491 492 a a DT 493 498 novel novel JJ 499 506 protein protein NN 507 511 that that WDT 512 524 specifically specifically RB 525 535 associates associate VBZ 536 540 with with IN 541 546 Oct-1 oct-1 NN 547 550 and and CC 551 556 Oct-2 oct-2 NN 556 557 . . . 558 569 Biochemical biochemical JJ 570 577 studies study NNS 578 589 demonstrate demonstrate VBP 590 594 that that IN 595 600 OBF-1 obf-1 NN 601 604 has have VBZ 605 607 no no DT 608 617 intrinsic intrinsic JJ 618 629 DNA-binding dna-binding JJ 630 638 activity activity NN 639 642 and and CC 643 653 recognizes recognize VBZ 654 657 the the DT 658 661 POU POU NNP 662 669 domains domain NNS 670 672 of of IN 673 678 Oct-1 oct-1 NN 679 682 and and CC 683 688 Oct-2 oct-2 NN 688 689 , , , 690 693 but but CC 694 697 not not RB 698 703 those those DT 704 706 of of IN 707 712 Oct-4 oct-4 NN 713 716 and and CC 717 722 Oct-6 Oct-6 NNP 722 723 . . . 724 727 The the DT 728 733 OBF-1 OBF-1 NNP 734 738 mRNA mRNA NNP 739 741 is be VBZ 742 751 expressed express VBN 752 754 in in IN 755 756 a a DT 757 763 highly highly RB 764 777 cell-specific cell-specific JJ 778 784 manner manner NN 784 785 , , , 786 791 being be VBG 792 796 most most RBS 797 805 abundant abundant JJ 806 808 in in IN 809 810 B B NNP 811 816 cells cell NNS 817 820 and and CC 821 832 essentially essentially RB 833 839 absent absent JJ 840 842 in in IN 843 847 most most JJS 848 850 of of IN 851 854 the the DT 855 860 other other JJ 861 866 cells cell NNS 867 869 or or CC 870 877 tissues tissue NNS 878 884 tested test VBN 884 885 . . . 886 897 Furthermore furthermore RB 897 898 , , , 899 909 expression expression NN 910 912 of of IN 913 918 OBF-1 obf-1 NN 919 921 in in IN 922 926 HeLa HeLa NNP 927 932 cells cell NNS 933 944 selectively selectively RB 945 955 stimulates stimulate VBZ 956 959 the the DT 960 968 activity activity NN 969 971 of of IN 972 973 a a DT 974 981 natural natural JJ 982 996 immunoglobulin immunoglobulin NN 997 1005 promoter promoter NN 1006 1008 in in IN 1009 1011 an an DT 1012 1019 octamer octamer NN 1020 1034 site-dependent site-dependent JJ 1035 1041 manner manner NN 1041 1042 . . . 1043 1047 Thus thus RB 1047 1048 , , , 1049 1054 OBF-1 OBF-1 NNP 1055 1058 has have VBZ 1059 1062 all all PDT 1063 1066 the the DT 1067 1077 properties property NNS 1078 1086 expected expect VBN 1087 1090 for for IN 1091 1092 a a DT 1093 1094 B B NNP 1095 1108 cell-specific cell-specific JJ 1109 1124 transcriptional transcriptional JJ 1125 1136 coactivator coactivator NN 1137 1144 protein protein NN 1144 1145 . . .