0 1 c c SYM 1 2 - - : 2 5 Myb Myb NNP 6 9 and and CC 10 13 Ets Ets NNP 14 22 proteins protein NNS 23 32 synergize synergize VBP 33 35 to to TO 36 44 overcome overcome VB 45 60 transcriptional transcriptional JJ 61 71 repression repression NN 72 74 by by IN 75 78 ZEB ZEB NNP 78 79 . . . 81 84 The the DT 85 88 Zfh Zfh NNP 89 95 family family NN 96 98 of of IN 99 103 zinc zinc NN 104 122 finger/homeodomain finger/homeodomain NN 123 131 proteins protein NNS 132 135 was be VBD 136 141 first first RB 142 152 identified identify VBN 153 155 in in IN 156 166 Drosophila drosophila FW 167 172 where where WRB 173 175 it it PRP 176 178 is be VBZ 179 187 required require VBN 188 191 for for IN 192 207 differentiation differentiation NN 208 210 of of IN 211 218 tissues tissue NNS 219 223 such such JJ 224 226 as as IN 227 230 the the DT 231 238 central central JJ 239 246 nervous nervous JJ 247 253 system system NN 254 257 and and CC 258 264 muscle muscle NN 264 265 . . . 266 269 ZEB ZEB NNP 269 270 , , , 271 272 a a DT 273 283 vertebrate vertebrate JJ 284 291 homolog homolog NN 292 294 of of IN 295 300 Zfh-1 Zfh-1 NNP 300 301 , , , 302 307 binds bind VBZ 308 309 a a DT 310 316 subset subset NN 317 319 of of IN 320 321 E e NN 322 327 boxes box NNS 328 331 and and CC 332 338 blocks block VBZ 339 349 myogenesis myogenesis NN 350 357 through through IN 358 373 transcriptional transcriptional JJ 374 384 repression repression NN 385 387 of of IN 388 394 muscle muscle NN 395 400 genes gene NNS 400 401 . . . 402 404 We we PRP 405 412 present present VBP 413 421 evidence evidence NN 422 426 here here RB 427 431 that that IN 432 435 ZEB ZEB NNP 436 440 also also RB 441 444 has have VBZ 445 447 an an DT 448 457 important important JJ 458 462 role role NN 463 465 in in IN 466 477 controlling control VBG 478 491 hematopoietic hematopoietic JJ 492 496 gene gene NN 497 510 transcription transcription NN 510 511 . . . 512 515 Two two CD 516 524 families family NNS 525 527 of of IN 528 541 transcription transcription NN 542 549 factors factor NNS 550 554 that that WDT 555 558 are be VBP 559 567 required require VBN 568 571 for for IN 572 578 normal normal JJ 579 592 hematopoiesis hematopoiesis NN 593 596 are be VBP 597 602 c-Myb c-myb NN 603 606 and and CC 607 610 Ets ets NN 610 611 . . . 612 617 These these DT 618 625 factors factor NNS 626 629 act act VBP 630 645 synergistically synergistically RB 646 648 to to TO 649 657 activate activate VB 658 671 transcription transcription NN 671 672 , , , 673 676 and and CC 677 681 this this DT 682 689 synergy synergy NN 690 692 is be VBZ 693 701 required require VBN 702 705 for for IN 706 719 transcription transcription NN 720 722 of of IN 723 725 at at IN 726 731 least least JJS 732 739 several several JJ 740 749 important important JJ 750 763 hematopoietic hematopoietic JJ 764 769 genes gene NNS 769 770 . . . 771 774 ZEB ZEB NNP 775 781 blocks block VBZ 782 785 the the DT 786 794 activity activity NN 795 797 of of IN 798 803 c-Myb c-myb NN 804 807 and and CC 808 811 Ets ets NN 812 824 individually individually RB 824 825 , , , 826 829 but but CC 830 838 together together RB 839 842 the the DT 843 850 factors factor NNS 851 860 synergize synergize VBP 861 863 to to TO 864 870 resist resist VB 871 875 this this DT 876 886 repression repression NN 886 887 . . . 888 892 Such such JJ 893 903 repression repression NN 904 911 imposes impose VBZ 912 913 a a DT 914 925 requirement requirement NN 926 929 for for IN 930 934 both both CC 935 940 c-Myb c-myb NN 941 944 and and CC 945 948 Ets ets NN 949 952 for for IN 953 968 transcriptional transcriptional JJ 969 977 activity activity NN 977 978 , , , 979 988 providing provide VBG 989 992 one one CD 993 1004 explanation explanation NN 1005 1008 for for IN 1009 1012 why why WRB 1013 1020 synergy synergy NN 1021 1028 between between IN 1029 1034 these these DT 1035 1042 factors factor NNS 1043 1045 is be VBZ 1046 1055 important important JJ 1055 1056 . . . 1057 1060 The the DT 1061 1068 balance balance NN 1069 1076 between between IN 1077 1087 repression repression NN 1088 1090 by by IN 1091 1094 ZEB ZEB NNP 1095 1098 and and CC 1099 1114 transcriptional transcriptional JJ 1115 1125 activation activation NN 1126 1128 by by IN 1129 1138 c-Myb/Ets c-myb/ets NN 1139 1147 provides provide VBZ 1148 1149 a a DT 1150 1158 flexible flexible JJ 1159 1169 regulatory regulatory JJ 1170 1179 mechanism mechanism NN 1180 1183 for for IN 1184 1195 controlling control VBG 1196 1200 gene gene NN 1201 1211 expression expression NN 1212 1214 in in IN 1215 1228 hematopoietic hematopoietic JJ 1229 1234 cells cell NNS 1234 1235 . . . 1236 1238 We we PRP 1239 1250 demonstrate demonstrate VBP 1251 1255 that that IN 1256 1259 one one CD 1260 1266 target target NN 1267 1269 of of IN 1270 1274 this this DT 1275 1292 positive/negative positive/negative JJ 1293 1303 regulation regulation NN 1304 1306 in in FW 1307 1311 vivo vivo FW 1312 1314 is be VBZ 1315 1318 the the DT 1319 1325 alpha4 alpha4 NN 1326 1334 integrin integrin NN 1334 1335 , , , 1336 1341 which which WDT 1342 1346 play play VBP 1347 1348 a a DT 1349 1352 key key JJ 1353 1357 role role NN 1358 1360 in in IN 1361 1367 normal normal JJ 1368 1381 hematopoiesis hematopoiesis NN 1382 1385 and and CC 1386 1394 function function NN 1395 1397 of of IN 1398 1404 mature mature JJ 1405 1415 leukocytes leukocyte NNS 1415 1416 . . .