0 10 Expression expression NN 11 13 of of IN 14 19 tal-1 tal-1 NN 20 23 and and CC 24 36 GATA-binding gata-binding JJ 37 45 proteins protein NNS 46 52 during during IN 53 58 human human JJ 59 72 hematopoiesis hematopoiesis NN 72 73 . . . 75 80 Tal-1 tal-1 NN 81 95 rearrangements rearrangement NNS 96 99 are be VBP 100 110 associated associate VBN 111 115 with with IN 116 122 nearly nearly RB 123 125 30 30 CD 125 126 % % NN 127 129 of of IN 130 135 human human JJ 136 137 T t NN 138 143 acute acute JJ 144 157 lymphoblastic lymphoblastic JJ 158 166 leukemia leukemia NN 166 167 . . . 168 173 Tal-1 tal-1 NN 174 178 gene gene NN 179 186 encodes encode VBZ 187 188 a a DT 189 197 putative putative JJ 198 211 transcription transcription NN 212 218 factor factor NN 219 223 with with IN 224 225 a a DT 226 231 basic basic JJ 232 248 helix-loop-helix helix-loop-helix JJ 249 255 domain domain NN 256 259 and and CC 260 262 is be VBZ 263 268 known know VBN 269 271 to to TO 272 274 be be VB 275 288 predominantly predominantly RB 289 298 expressed express VBN 299 301 in in IN 302 315 hematopoietic hematopoietic JJ 316 321 cells cell NNS 321 322 . . . 323 325 We we PRP 326 338 investigated investigate VBD 339 342 the the DT 343 350 pattern pattern NN 351 353 of of IN 354 359 tal-1 tal-1 NN 360 370 expression expression NN 371 373 in in IN 374 382 purified purify VBN 383 388 human human JJ 389 402 hematopoietic hematopoietic JJ 403 408 cells cell NNS 409 411 by by IN 412 414 in in FW 415 419 situ situ FW 420 433 hybridization hybridization NN 434 437 and and CC 438 445 reverse reverse JJ 446 459 transcriptase transcriptase NN 460 470 polymerase polymerase NN 471 476 chain chain NN 477 485 reaction reaction NN 486 494 analysis analysis NN 494 495 . . . 496 500 Both both DT 501 508 methods method NNS 509 521 demonstrated demonstrate VBD 522 526 that that IN 527 530 the the DT 531 536 tal-1 tal-1 NN 537 541 gene gene NN 542 544 is be VBZ 545 554 expressed express VBN 555 557 in in IN 558 572 megakaryocytes megakaryocyte NNS 573 576 and and CC 577 590 erythroblasts erythroblast NNS 591 593 as as RB 594 598 well well RB 599 601 as as IN 602 604 in in IN 605 615 basophilic basophilic JJ 616 628 granulocytes granulocyte NNS 628 629 . . . 630 632 In in IN 633 641 addition addition NN 641 642 , , , 643 646 our our PRP$ 647 654 results result NNS 655 663 indicate indicate VBP 664 668 that that IN 669 672 the the DT 673 678 tal-1 tal-1 NN 679 681 1A 1a NN 682 690 promoter promoter NN 690 691 , , , 692 697 which which WDT 698 706 contains contain VBZ 707 710 two two CD 711 720 consensus consensus NN 721 733 GATA-binding gata-binding JJ 734 739 sites site NNS 739 740 , , , 741 743 is be VBZ 744 750 active active JJ 751 757 mainly mainly RB 758 760 in in IN 761 766 these these DT 767 775 lineages lineage NNS 775 776 . . . 777 784 Because because IN 785 788 the the DT 789 795 GATA-1 gata-1 NN 796 800 gene gene NN 801 803 is be VBZ 804 809 known know VBN 810 812 to to TO 813 826 transactivate transactivate VB 827 834 several several JJ 835 840 genes gene NNS 841 849 specific specific JJ 850 853 for for IN 854 857 the the DT 858 867 erythroid erythroid JJ 867 868 , , , 869 883 megakaryocytic megakaryocytic JJ 883 884 , , , 885 888 and and CC 889 910 mastocytic/basophilic mastocytic/basophilic JJ 911 919 lineages lineage NNS 919 920 , , , 921 923 we we PRP 924 931 studied study VBD 932 938 GATA-1 gata-1 NN 939 949 expression expression NN 950 952 in in IN 953 958 these these DT 959 967 purified purify VBN 968 981 hematopoietic hematopoietic JJ 982 987 cells cell NNS 987 988 . . . 989 991 We we PRP 992 997 found find VBD 998 1002 that that IN 1003 1009 GATA-1 gata-1 NN 1010 1013 and and CC 1014 1019 tal-1 tal-1 NN 1020 1025 genes gene NNS 1026 1029 are be VBP 1030 1041 coexpressed coexpresse VBN 1042 1044 in in IN 1045 1050 these these DT 1051 1056 three three CD 1057 1065 lineages lineage NNS 1065 1066 . . . 1067 1077 Remarkably remarkably RB 1077 1078 , , , 1079 1082 the the DT 1083 1093 expression expression NN 1094 1096 of of IN 1097 1101 both both DT 1102 1107 genes gene NNS 1108 1110 is be VBZ 1111 1124 downmodulated downmodulate VBN 1125 1131 during during IN 1132 1141 erythroid erythroid JJ 1142 1145 and and CC 1146 1160 megakaryocytic megakaryocytic JJ 1161 1169 terminal terminal JJ 1170 1180 maturation maturation NN 1180 1181 . . . 1182 1184 In in IN 1185 1193 immature immature JJ 1194 1207 hematopoietic hematopoietic JJ 1208 1213 cells cell NNS 1213 1214 , , , 1215 1220 tal-1 tal-1 NN 1221 1224 and and CC 1225 1231 GATA-1 gata-1 NN 1232 1237 genes gene NNS 1238 1241 are be VBP 1242 1253 coexpressed coexpresse VBN 1254 1256 in in IN 1257 1266 committed commit VBN 1267 1278 progenitors progenitor NNS 1279 1284 cells cell NNS 1285 1286 ( ( ( 1286 1301 CD34+/CD38(2+)) CD34+/CD38(2+)) NNP 1301 1302 , , , 1303 1310 whereas whereas IN 1311 1315 they they PRP 1316 1319 are be VBP 1320 1323 not not RB 1324 1334 detectable detectable JJ 1335 1337 in in IN 1338 1341 the the DT 1342 1346 most most RBS 1347 1356 primitive primitive JJ 1357 1362 cells cell NNS 1363 1364 ( ( ( 1364 1379 CD34(2+)/CD38-) cd34(2+)/cd38-) JJ 1379 1380 . . . 1381 1383 In in IN 1384 1392 contrast contrast NN 1392 1393 , , , 1394 1400 GATA-2 gata-2 NN 1401 1403 is be VBZ 1404 1412 strongly strongly RB 1413 1422 expressed express VBN 1423 1425 in in IN 1426 1430 both both CC 1431 1435 most most RBS 1436 1445 primitive primitive JJ 1446 1449 and and CC 1450 1459 committed commit VBN 1460 1471 progenitors progenitor NNS 1472 1477 cells cell NNS 1477 1478 , , , 1479 1486 whereas whereas IN 1487 1493 GATA-3 GATA-3 NNP 1494 1496 is be VBZ 1497 1503 mostly mostly RB 1504 1512 detected detect VBN 1513 1515 in in IN 1516 1520 most most JJS 1521 1530 primitive primitive JJ 1531 1535 ones one NNS 1535 1536 . . . 1537 1547 Altogether altogether RB 1548 1551 our our PRP$ 1552 1559 results result NNS 1560 1568 strongly strongly RB 1569 1576 suggest suggest VBP 1577 1581 that that IN 1582 1588 GATA-1 gata-1 NN 1589 1598 modulates modulate VBZ 1599 1602 the the DT 1603 1616 transcription transcription NN 1617 1619 of of IN 1620 1625 tal-1 tal-1 NN 1626 1632 during during IN 1633 1636 the the DT 1637 1652 differentiation differentiation NN 1653 1655 of of IN 1656 1659 the the DT 1660 1669 erythroid erythroid JJ 1669 1670 , , , 1671 1685 megakaryocytic megakaryocytic JJ 1685 1686 , , , 1687 1690 and and CC 1691 1703 basosophilic basosophilic JJ 1704 1712 lineages lineage NNS 1712 1713 . . .