0 7 Ectopic ectopic JJ 8 18 expression expression NN 19 21 of of IN 22 23 a a DT 24 35 conditional conditional JJ 36 51 GATA-2/estrogen GATA-2/estrogen NNP 52 60 receptor receptor NN 61 68 chimera chimera NN 69 76 arrests arrest VBZ 77 86 erythroid erythroid JJ 87 102 differentiation differentiation NN 103 105 in in IN 106 107 a a DT 108 125 hormone-dependent hormone-dependent JJ 126 132 manner manner NN 132 133 . . . 135 138 The the DT 139 143 GATA GATA NNP 144 151 factors factor NNS 152 155 are be VBP 156 157 a a DT 158 164 family family NN 165 167 of of IN 168 183 transcriptional transcriptional JJ 184 194 regulatory regulatory JJ 195 203 proteins protein NNS 204 206 in in IN 207 217 eukaryotes eukaryote NNS 218 222 that that WDT 223 228 share share VBP 229 238 extensive extensive JJ 239 247 homology homology NN 248 250 in in IN 251 256 their their PRP$ 257 268 DNA-binding dna-binding JJ 269 276 domains domain NNS 276 277 . . . 278 281 One one CD 282 291 enigmatic enigmatic JJ 292 298 aspect aspect NN 299 301 of of IN 302 306 GATA GATA NNP 307 313 factor factor NN 314 324 expression expression NN 325 327 is be VBZ 328 332 that that IN 333 340 several several JJ 341 345 GATA GATA NNP 346 354 proteins protein NNS 354 355 , , , 356 361 which which WDT 362 372 ostensibly ostensibly RB 373 378 share share VBP 379 382 the the DT 383 387 same same JJ 388 399 DNA-binding dna-binding JJ 400 404 site site NN 405 416 specificity specificity NN 416 417 , , , 418 421 are be VBP 422 433 coexpressed coexpresse VBN 434 436 in in IN 437 446 erythroid erythroid JJ 447 452 cells cell NNS 452 453 . . . 454 456 To to TO 457 466 elucidate elucidate VB 467 470 the the DT 471 476 roles role NNS 477 479 of of IN 480 490 individual individual JJ 491 495 GATA GATA NNP 496 503 factors factor NNS 504 506 in in IN 507 521 erythropoiesis erythropoiesis NN 521 522 , , , 523 534 conditional conditional JJ 535 542 alleles allele NNS 543 545 of of IN 546 552 GATA-1 gata-1 NN 552 553 , , , 554 560 GATA-2 gata-2 NN 560 561 , , , 562 565 and and CC 566 572 GATA-3 GATA-3 NNP 573 577 were be VBD 578 586 prepared prepare VBN 587 589 by by IN 590 596 fusing fuse VBG 597 601 each each DT 602 604 of of IN 605 608 the the DT 609 616 factors factor NNS 617 619 to to TO 620 623 the the DT 624 639 hormone-binding hormone-binding JJ 640 646 domain domain NN 647 649 of of IN 650 653 the the DT 654 659 human human JJ 660 668 estrogen estrogen NN 669 677 receptor receptor NN 678 679 ( ( ( 679 681 ER ER NNP 681 682 ) ) ) 682 683 . . . 684 689 These these DT 690 697 GATA/ER gata/er NN 698 706 chimeric chimeric JJ 707 714 factors factor NNS 715 719 were be VBD 720 725 shown show VBN 726 728 to to TO 729 731 be be VB 732 749 hormone-inducible hormone-inducible JJ 750 766 trans-activating trans-activating JJ 767 775 proteins protein NNS 776 778 in in IN 779 788 transient transient JJ 789 801 transfection transfection NN 802 808 assays assay NNS 808 809 . . . 810 814 When when WRB 815 821 stably stably RB 822 832 introduced introduce VBN 833 837 into into IN 838 845 primary primary JJ 846 859 erythroblasts erythroblast NNS 860 862 or or CC 863 876 conditionally conditionally RB 877 888 transformed transform VBN 889 898 erythroid erythroid JJ 899 910 progenitors progenitor NNS 911 916 cells cell NNS 916 917 , , , 918 927 exogenous exogenous JJ 928 937 GATA-2/ER gata-2/er NN 938 946 promoted promote VBD 947 960 proliferation proliferation NN 961 964 and and CC 965 974 inhibited inhibit VBD 975 983 terminal terminal JJ 984 999 differentiation differentiation NN 1000 1002 in in IN 1003 1005 an an DT 1006 1024 estrogen-dependent estrogen-dependent JJ 1025 1031 manner manner NN 1031 1032 . . . 1033 1038 These these DT 1039 1049 phenotypic phenotypic JJ 1050 1057 effects effect NNS 1058 1061 are be VBP 1062 1074 specifically specifically RB 1075 1087 attributable attributable JJ 1088 1090 to to TO 1091 1094 the the DT 1095 1101 action action NN 1102 1104 of of IN 1105 1116 ectopically ectopically RB 1117 1126 expressed express VBN 1127 1136 GATA-2/ER gata-2/er NN 1137 1144 because because IN 1145 1158 erythroblasts erythroblast NNS 1159 1169 expressing express VBG 1170 1179 exogenous exogenous JJ 1180 1186 GATA-2 gata-2 NN 1187 1190 are be VBP 1191 1205 constitutively constitutively RB 1206 1214 arrested arrest VBN 1215 1217 in in IN 1218 1233 differentiation differentiation NN 1234 1237 and and CC 1238 1245 because because IN 1246 1255 erythroid erythroid JJ 1256 1267 progenitors progenitor NNS 1268 1278 expressing express VBG 1279 1285 either either CC 1286 1292 Gal/ER Gal/ER NNP 1293 1295 or or CC 1296 1305 GATA-3/ER GATA-3/ER NNP 1306 1308 do do VBP 1309 1312 not not RB 1313 1320 display display VB 1321 1322 a a DT 1323 1341 hormone-responsive hormone-responsive JJ 1342 1347 block block NN 1348 1350 in in IN 1351 1366 differentiation differentiation NN 1366 1367 . . . 1368 1372 Thus thus RB 1372 1373 , , , 1374 1377 the the DT 1378 1384 GATA-2 gata-2 NN 1385 1398 transcription transcription NN 1399 1405 factor factor NN 1406 1413 appears appear VBZ 1414 1416 to to TO 1417 1421 play play VB 1422 1423 a a DT 1424 1428 role role NN 1429 1431 in in IN 1432 1442 regulating regulate VBG 1443 1446 the the DT 1447 1459 self-renewal self-renewal JJ 1460 1468 capacity capacity NN 1469 1471 of of IN 1472 1477 early early JJ 1478 1487 erythroid erythroid JJ 1488 1498 progenitor progenitor NN 1499 1504 cells cell NNS 1504 1505 . . .