0 7 Various various JJ 8 13 modes mode NNS 14 16 of of IN 17 22 basic basic JJ 23 39 helix-loop-helix helix-loop-helix JJ 40 56 protein-mediated protein-mediated JJ 57 67 regulation regulation NN 68 70 of of IN 71 77 murine murine JJ 78 86 leukemia leukemia NN 87 92 virus virus NN 93 106 transcription transcription NN 107 109 in in IN 110 118 lymphoid lymphoid JJ 119 123 cell cell NN 124 129 lines line NNS 129 130 . . . 132 135 The the DT 136 153 transcriptionally transcriptionally RB 154 164 regulatory regulatory JJ 165 172 regions region NNS 173 175 of of IN 176 179 the the DT 180 193 lymphomagenic lymphomagenic JJ 194 197 Akv Akv NNP 198 201 and and CC 202 207 SL3-3 SL3-3 NNP 208 214 murine murine JJ 215 223 leukemia leukemia NN 224 236 retroviruses retrovirus NNS 237 238 ( ( ( 238 242 MLVs MLV NNPS 242 243 ) ) ) 244 251 contain contain VBP 252 255 two two CD 256 261 types type NNS 262 264 of of IN 265 270 E-box e-box NN 271 280 consensus consensus NN 281 287 motifs motif NNS 287 288 , , , 289 295 CAGATG CAGATG NNP 295 296 . . . 297 300 One one CD 301 305 type type NN 305 306 , , , 307 311 EA/S EA/S NNP 311 312 , , , 313 315 is be VBZ 316 323 located located JJ 324 326 in in IN 327 330 the the DT 331 339 upstream upstream JJ 340 348 promoter promoter NN 349 355 region region NN 355 356 , , , 357 360 and and CC 361 364 the the DT 365 370 other other JJ 370 371 , , , 372 378 E(gre) E(gre) NNP 378 379 , , , 380 382 is be VBZ 383 390 located located JJ 391 393 in in IN 394 395 a a DT 396 402 tandem tandem JJ 403 409 repeat repeat NN 410 414 with with IN 415 423 enhancer enhancer NN 424 434 properties property NNS 434 435 . . . 436 438 We we PRP 439 443 have have VBP 444 452 examined examine VBN 453 456 the the DT 457 469 requirements requirement NNS 470 472 of of IN 473 476 the the DT 477 487 individual individual JJ 488 495 E-boxes e-box NNS 496 498 in in IN 499 502 MLV MLV NNP 503 518 transcriptional transcriptional JJ 519 529 regulation regulation NN 529 530 . . . 531 533 In in IN 534 542 lymphoid lymphoid JJ 543 547 cell cell NN 548 553 lines line NNS 554 558 only only RB 558 559 , , , 560 563 the the DT 564 578 E(gre)-binding e(gre)-binding JJ 579 586 protein protein NN 587 596 complexes complex NNS 597 605 included include VBD 606 610 ALF1 ALF1 NNP 611 613 or or CC 614 617 HEB HEB NNP 618 621 and and CC 622 625 E2A E2A NNP 626 631 basic basic JJ 632 648 helix-loop-helix helix-loop-helix JJ 649 657 proteins protein NNS 657 658 . . . 659 666 Ectopic ectopic JJ 667 671 ALF1 ALF1 NNP 672 675 and and CC 676 679 E2A E2A NNP 680 688 proteins protein NNS 689 697 required require VBD 698 704 intact intact JJ 705 711 E(gre) e(gre) NN 712 718 motifs motif NNS 719 722 for for IN 723 732 mediating mediate VBG 733 748 transcriptional transcriptional JJ 749 759 activation activation NN 759 760 . . . 761 765 ALF1 alf1 NN 766 780 transactivated transactivate VBD 781 794 transcription transcription NN 795 797 of of IN 798 801 Akv Akv NNP 802 805 MLV MLV NNP 806 813 through through IN 814 817 the the DT 818 821 two two CD 822 828 E(gre) e(gre) NN 829 835 motifs motif NNS 836 843 equally equally RB 843 844 , , , 845 852 whereas whereas IN 853 856 E2A E2A NNP 857 864 protein protein NN 865 873 required require VBD 874 877 the the DT 878 895 promoter-proximal promoter-proximal JJ 896 902 E(gre) e(gre) NN 903 908 motif motif NN 908 909 . . . 910 912 In in IN 913 915 T- T- NNP 916 919 and and CC 920 926 B-cell b-cell NN 927 932 lines line NNS 932 933 , , , 934 937 the the DT 938 944 E(gre) e(gre) NN 945 951 motifs motif NNS 952 956 were be VBD 957 959 of of IN 960 965 major major JJ 966 976 importance importance NN 977 980 for for IN 981 984 Akv Akv NNP 985 988 MLV MLV NNP 989 1004 transcriptional transcriptional JJ 1005 1013 activity activity NN 1013 1014 , , , 1015 1020 while while IN 1021 1024 the the DT 1025 1029 EA/S EA/S NNP 1030 1035 motif motif NN 1036 1039 had have VBD 1040 1044 some some DT 1045 1051 effect effect NN 1051 1052 . . . 1053 1055 In in IN 1056 1064 contrast contrast NN 1064 1065 , , , 1066 1073 neither neither CC 1074 1080 E(gre) E(gre) NNP 1081 1084 nor nor CC 1085 1089 EA/S EA/S NNP 1090 1096 motifs motif NNS 1097 1108 contributed contribute VBD 1109 1121 pronouncedly pronouncedly RB 1122 1124 to to TO 1125 1128 Akv Akv NNP 1129 1132 MLV MLV NNP 1133 1146 transcription transcription NN 1147 1149 in in IN 1150 1153 NIH NIH NNP 1154 1157 3T3 3t3 NN 1158 1163 cells cell NNS 1164 1171 lacking lack VBG 1172 1183 DNA-binding dna-binding JJ 1184 1188 ALF1 ALF1 NNP 1189 1191 or or CC 1192 1195 HEB HEB NNP 1196 1199 and and CC 1200 1203 E2A E2A NNP 1204 1212 proteins protein NNS 1212 1213 . . . 1214 1217 The the DT 1218 1221 Id1 id1 NN 1222 1229 protein protein NN 1230 1233 was be VBD 1234 1239 found find VBN 1240 1242 to to TO 1243 1250 repress repress VB 1251 1255 ALF1 alf1 NN 1256 1264 activity activity NN 1265 1267 in in FW 1268 1273 vitro vitro FW 1274 1277 and and CC 1278 1280 in in FW 1281 1285 vivo vivo FW 1285 1286 . . . 1287 1295 Moreover moreover RB 1295 1296 , , , 1297 1304 ectopic ectopic JJ 1305 1308 Id1 id1 NN 1309 1318 repressed repress VBD 1319 1334 E(gre)-directed e(gre)-directed JJ 1335 1338 but but CC 1339 1342 not not RB 1343 1356 EA/S-directed ea/s-directed JJ 1357 1360 MLV MLV NNP 1361 1374 transcription transcription NN 1375 1377 in in IN 1378 1386 lymphoid lymphoid JJ 1387 1391 cell cell NN 1392 1397 lines line NNS 1397 1398 . . . 1399 1401 In in IN 1402 1412 conclusion conclusion NN 1412 1413 , , , 1414 1420 E(gre) e(gre) NN 1421 1427 motifs motif NNS 1428 1431 and and CC 1432 1443 interacting interact VBG 1444 1449 basic basic JJ 1450 1466 helix-loop-helix helix-loop-helix JJ 1467 1475 proteins protein NNS 1476 1479 are be VBP 1480 1489 important important JJ 1490 1502 determinants determinant NNS 1503 1506 for for IN 1507 1510 MLV MLV NNP 1511 1526 transcriptional transcriptional JJ 1527 1535 activity activity NN 1536 1538 in in IN 1539 1550 lymphocytic lymphocytic JJ 1551 1555 cell cell NN 1556 1561 lines line NNS 1561 1562 . . .