0 6 v-erbA v-erba NN 7 21 overexpression overexpression NN 22 24 is be VBZ 25 33 required require VBN 34 36 to to TO 37 47 extinguish extinguish VB 48 54 c-erbA c-erba NN 55 63 function function NN 64 66 in in IN 67 76 erythroid erythroid JJ 77 81 cell cell NN 82 97 differentiation differentiation NN 98 101 and and CC 102 112 regulation regulation NN 113 115 of of IN 116 119 the the DT 120 124 erbA erba NN 125 131 target target NN 132 136 gene gene NN 137 141 CAII CAII NNP 141 142 . . . 144 147 The the DT 148 154 v-erbA v-erba NN 155 166 oncoprotein oncoprotein NN 167 177 represents represent VBZ 178 179 a a DT 180 201 retrovirus-transduced retrovirus-transduced JJ 202 211 oncogenic oncogenic JJ 212 219 version version NN 220 222 of of IN 223 226 the the DT 227 234 thyroid thyroid NN 235 242 hormone hormone NN 243 244 ( ( ( 244 249 T3/T4 t3/t4 NN 249 250 ) ) ) 251 259 receptor receptor NN 260 266 c-erbA c-erbA NNP 267 268 ( ( ( 268 272 type type NN 273 278 alpha alpha NN 278 279 ) ) ) 279 280 . . . 281 283 It it PRP 284 295 contributes contribute VBZ 296 298 to to TO 299 312 virus-induced virus-induced JJ 313 328 erythroleukemia erythroleukemia NN 329 331 by by IN 332 343 efficiently efficiently RB 344 353 arresting arrest VBG 354 369 differentiation differentiation NN 370 372 of of IN 373 376 red red JJ 377 381 cell cell NN 382 393 progenitors progenitor NNS 394 397 and and CC 398 400 by by IN 401 412 suppressing suppress VBG 413 426 transcription transcription NN 427 429 of of IN 430 450 erythrocyte-specific erythrocyte-specific JJ 451 456 genes gene NNS 456 457 . . . 458 462 Here here RB 462 463 , , , 464 466 we we PRP 467 471 show show VBP 472 476 that that IN 477 483 v-erbA v-erba NN 484 487 and and CC 488 494 c-erbA c-erba NN 495 499 bind bind VBP 500 508 directly directly RB 509 511 to to TO 512 521 sequences sequence NNS 522 528 within within IN 529 532 the the DT 533 541 promoter promoter NN 542 544 of of IN 545 548 the the DT 549 569 erythrocyte-specific erythrocyte-specific JJ 570 578 carbonic carbonic JJ 579 588 anhydrase anhydrase NN 589 591 II ii CD 592 593 ( ( ( 593 597 CAII CAII NNP 597 598 ) ) ) 598 599 , , , 600 601 a a DT 602 606 gene gene NN 607 612 whose whose WP$ 613 626 transcription transcription NN 627 629 is be VBZ 630 641 efficiently efficiently RB 642 652 suppressed suppress VBN 653 655 by by IN 656 662 v-erbA v-erbA NNP 662 663 . . . 664 668 This this DT 669 681 erbA-binding erba-binding JJ 682 686 site site NN 687 694 confers confer VBZ 695 702 thyroid thyroid NN 703 710 hormone hormone NN 711 725 responsiveness responsiveness NN 726 728 to to TO 729 730 a a DT 731 743 heterologous heterologous JJ 744 752 promoter promoter NN 753 755 in in IN 756 765 transient transient JJ 766 776 expression expression NN 777 788 experiments experiment NNS 789 792 and and CC 793 795 is be VBZ 796 797 a a DT 798 804 target target NN 805 808 for for IN 809 818 efficient efficient JJ 819 834 down-regulation down-regulation NN 835 837 of of IN 838 842 CAII CAII NNP 843 856 transcription transcription NN 857 859 by by IN 860 863 the the DT 864 870 v-erbA v-erba NN 871 882 oncoprotein oncoprotein NN 882 883 . . . 884 886 In in IN 887 893 stably stably RB 894 905 transformed transform VBN 906 919 erythroblasts erythroblast NNS 920 932 coexpressing coexpresse VBG 933 936 the the DT 937 943 v-erbA v-erba NN 944 955 oncoprotein oncoprotein NN 956 959 and and CC 960 963 the the DT 964 973 c-erbA/T3 c-erba/t3 NN 974 982 receptor receptor NN 983 985 at at IN 986 988 an an DT 989 1002 approximately approximately RB 1003 1012 equimolar equimolar JJ 1013 1018 ratio ratio NN 1018 1019 , , , 1020 1026 c-erbA c-erba NN 1027 1035 activity activity NN 1036 1038 is be VBZ 1039 1047 dominant dominant JJ 1048 1052 over over IN 1053 1059 v-erbA v-erbA NNP 1059 1060 . . . 1061 1063 T3 T3 NNP 1064 1075 efficiently efficiently RB 1076 1083 induced induce VBD 1084 1093 erythroid erythroid JJ 1094 1109 differentiation differentiation NN 1110 1112 in in IN 1113 1118 these these DT 1119 1124 cells cell NNS 1124 1125 , , , 1126 1130 thus thus RB 1131 1141 overcoming overcome VBG 1142 1145 the the DT 1146 1161 v-erbA-mediated v-erba-mediated JJ 1162 1177 differentiation differentiation NN 1178 1184 arrest arrest NN 1184 1185 . . . 1186 1194 Likewise likewise RB 1194 1195 , , , 1196 1198 T3 T3 NNP 1199 1208 activated activate VBD 1209 1213 CAII CAII NNP 1214 1227 transcription transcription NN 1228 1230 as as RB 1231 1235 well well RB 1236 1238 as as IN 1239 1248 transient transient JJ 1249 1259 expression expression NN 1260 1262 of of IN 1263 1264 a a DT 1265 1278 T3-responsive t3-responsive JJ 1279 1287 reporter reporter NN 1288 1292 gene gene NN 1293 1303 containing contain VBG 1304 1307 the the DT 1308 1321 CAII-specific caii-specific JJ 1322 1334 erbA-binding erba-binding JJ 1335 1339 site site NN 1339 1340 . . . 1341 1344 The the DT 1345 1361 c-erbA-dependent c-erba-dependent JJ 1362 1372 activation activation NN 1373 1375 of of IN 1376 1380 this this DT 1381 1385 CAII CAII NNP 1386 1394 reporter reporter NN 1395 1404 construct construct NN 1405 1410 could could MD 1411 1415 only only RB 1416 1418 be be VB 1419 1429 suppressed suppress VBN 1430 1432 by by IN 1433 1437 very very RB 1438 1442 high high JJ 1443 1450 amounts amount NNS 1451 1453 of of IN 1454 1460 v-erbA v-erbA NNP 1460 1461 . . . 1462 1465 Our our PRP$ 1466 1473 results result NNS 1474 1481 suggest suggest VBP 1482 1486 that that IN 1487 1501 overexpression overexpression NN 1502 1504 of of IN 1505 1511 v-erbA v-erbA NNP 1512 1514 is be VBZ 1515 1523 required require VBN 1524 1527 for for IN 1528 1531 its its PRP$ 1532 1540 function function NN 1541 1543 as as IN 1544 1546 an an DT 1547 1558 oncoprotein oncoprotein NN 1558 1559 . . .