0 3 The the DT 4 12 internal internal JJ 13 23 methionine methionine NN 24 30 codons codon NNS 31 33 of of IN 34 39 human human JJ 40 46 T-cell t-cell NN 47 55 leukemia leukemia NN 56 61 virus virus NN 62 66 type type NN 67 69 II ii CD 70 73 rex rex NN 74 78 gene gene NN 79 82 are be VBP 83 86 not not RB 87 95 required require VBN 96 99 for for IN 100 106 p24rex p24rex NN 107 117 production production NN 118 120 or or CC 121 126 virus virus NN 127 138 replication replication NN 139 142 and and CC 143 157 transformation transformation NN 157 158 . . . 160 165 Human human JJ 166 172 T-cell T-cell NNP 173 181 leukemia leukemia NN 182 187 virus virus NN 188 193 types type NNS 194 195 I i NN 196 197 ( ( ( 197 203 HTLV-I HTLV-I NNP 203 204 ) ) ) 205 208 and and CC 209 211 II ii CD 212 213 ( ( ( 213 220 HTLV-II HTLV-II NNP 220 221 ) ) ) 222 226 have have VBP 227 230 two two CD 231 244 nonstructural nonstructural JJ 245 257 trans-acting trans-acting JJ 258 268 regulatory regulatory JJ 269 274 genes gene NNS 274 275 , , , 276 279 tax tax NN 280 283 and and CC 284 287 rex rex NN 287 288 , , , 289 296 located located JJ 297 299 in in IN 300 303 the the DT 304 305 3 3 CD 305 306 ’ ' SYM 307 313 region region NN 314 316 of of IN 317 320 the the DT 321 326 viral viral JJ 327 333 genome genome NN 333 334 . . . 335 338 The the DT 339 342 tax tax NN 343 347 gene gene NN 348 355 product product NN 356 357 ( ( ( 357 363 HTLV-I HTLV-I NNP 364 370 p40tax p40tax NN 371 374 and and CC 375 382 HTLV-II HTLV-II NNP 383 389 p37tax p37tax NN 389 390 ) ) ) 391 393 is be VBZ 394 397 the the DT 398 413 transcriptional transcriptional JJ 414 423 activator activator NN 424 426 of of IN 427 430 the the DT 431 436 viral viral JJ 437 441 long long JJ 442 450 terminal terminal JJ 451 457 repeat repeat NN 457 458 . . . 459 462 The the DT 463 466 rex rex NN 467 471 gene gene NN 472 479 encodes encode VBZ 480 483 two two CD 484 491 protein protein NN 492 500 products product NNS 500 501 , , , 502 515 p27rex/p21rex p27rex/p21rex NN 516 519 and and CC 520 533 p26rex/p24rex p26rex/p24rex NN 534 536 in in IN 537 543 HTLV-I HTLV-I NNP 544 547 and and CC 548 555 HTLV-II HTLV-II NNP 555 556 , , , 557 569 respectively respectively RB 569 570 . . . 571 574 Rex Rex NNP 575 579 acts act VBZ 580 601 posttranscriptionally posttranscriptionally RB 602 604 to to TO 605 615 facilitate facilitate VB 616 628 accumulation accumulation NN 629 631 of of IN 632 643 full-length full-length JJ 644 651 gag/pol gag/pol NN 652 655 and and CC 656 662 singly singly RB 663 670 spliced splice VBN 671 674 env env NN 675 679 mRNA mrna NN 680 682 in in IN 683 686 the the DT 687 696 cytoplasm cytoplasm NN 697 699 of of IN 700 713 HTLV-infected htlv-infected JJ 714 719 cells cell NNS 719 720 . . . 721 729 Previous previous JJ 730 737 studies study NNS 738 744 showed show VBD 745 749 that that IN 750 753 the the DT 754 759 first first JJ 760 763 ATG atg NN 764 766 of of IN 767 770 the the DT 771 774 rex rex NN 775 779 gene gene NN 780 782 is be VBZ 783 791 critical critical JJ 792 795 for for IN 796 799 Rex Rex NNP 800 810 production production NN 811 814 and and CC 815 823 function function NN 823 824 . . . 825 828 The the DT 829 839 importance importance NN 840 842 of of IN 843 846 the the DT 847 855 internal internal JJ 856 860 ATGs atg NNS 861 863 to to TO 864 867 Rex Rex NNP 868 876 function function NN 877 879 is be VBZ 880 883 not not RB 884 889 known know VBN 889 890 . . . 891 898 However however RB 898 899 , , , 900 902 in in FW 903 908 vitro vitro FW 909 920 mutagenesis mutagenesis NN 921 923 of of IN 924 927 the the DT 928 934 HTLV-I HTLV-I NNP 935 938 rex rex NN 939 943 gene gene NN 944 947 has have VBZ 948 956 provided provide VBN 957 965 indirect indirect JJ 966 974 evidence evidence NN 975 980 which which WDT 981 989 suggests suggest VBZ 990 994 that that IN 995 1001 p21rex p21rex NN 1001 1002 , , , 1003 1006 and and CC 1007 1009 by by IN 1010 1017 analogy analogy NN 1018 1025 HTLV-II HTLV-II NNP 1026 1032 p24rex p24rex NN 1032 1033 , , , 1034 1041 results result VBZ 1042 1046 from from IN 1047 1057 initiation initiation NN 1058 1060 at at IN 1061 1063 an an DT 1064 1072 internal internal JJ 1073 1076 AUG aug NN 1077 1079 of of IN 1080 1083 the the DT 1084 1091 tax/rex tax/rex NN 1092 1096 mRNA mrna NN 1096 1097 . . . 1098 1100 By by IN 1101 1106 using use VBG 1107 1109 an an DT 1110 1120 infectious infectious JJ 1121 1130 molecular molecular JJ 1131 1136 clone clone NN 1137 1139 of of IN 1140 1147 HTLV-II HTLV-II NNP 1147 1148 , , , 1149 1151 we we PRP 1152 1164 investigated investigate VBD 1165 1168 the the DT 1169 1179 importance importance NN 1180 1182 of of IN 1183 1186 the the DT 1187 1195 internal internal JJ 1196 1200 ATGs atg NNS 1201 1203 of of IN 1204 1207 the the DT 1208 1211 rex rex NN 1212 1216 gene gene NN 1217 1219 on on IN 1220 1223 Rex Rex NNP 1224 1231 protein protein NN 1232 1242 production production NN 1243 1246 and and CC 1247 1255 function function NN 1255 1256 . . . 1257 1260 Our our PRP$ 1261 1268 results result NNS 1269 1277 indicate indicate VBP 1278 1282 that that IN 1283 1289 p24rex p24rex NN 1290 1292 of of IN 1293 1300 HTLV-II HTLV-II NNP 1301 1303 is be VBZ 1304 1307 not not RB 1308 1317 initiated initiate VBN 1318 1320 at at IN 1321 1323 an an DT 1324 1332 internal internal JJ 1333 1336 AUG aug NN 1337 1340 and and CC 1341 1345 that that IN 1346 1349 the the DT 1350 1358 internal internal JJ 1359 1369 methionine methionine NN 1370 1376 codons codon NNS 1377 1380 are be VBP 1381 1384 not not RB 1385 1392 crucial crucial JJ 1393 1395 to to TO 1396 1399 the the DT 1400 1408 function function NN 1409 1411 of of IN 1412 1415 the the DT 1416 1419 rex rex NN 1420 1424 gene gene NN 1425 1428 and and CC 1428 1429 , , , 1430 1440 ultimately ultimately RB 1440 1441 , , , 1442 1445 the the DT 1446 1458 transforming transform VBG 1459 1469 properties property NNS 1470 1472 of of IN 1473 1476 the the DT 1477 1482 virus virus NN 1482 1483 . . .