0 9 USF/c-Myc USF/c-Myc NNP 10 18 enhances enhance VBZ 18 19 , , , 20 25 while while IN 26 34 Yin-Yang yin-yang NN 35 36 1 1 CD 37 47 suppresses suppress VBZ 47 48 , , , 49 52 the the DT 53 61 promoter promoter NN 62 70 activity activity NN 71 73 of of IN 74 79 CXCR4 CXCR4 NNP 79 80 , , , 81 82 a a DT 83 93 coreceptor coreceptor NN 94 97 for for IN 98 103 HIV-1 HIV-1 NNP 104 109 entry entry NN 109 110 . . . 112 125 Transcription Transcription NNP 126 133 factors factor NNS 134 138 USF1 USF1 NNP 139 142 and and CC 143 147 USF2 USF2 NNP 148 159 up-regulate up-regulate VBP 160 164 gene gene NN 165 175 expression expression NN 176 177 ( ( ( 177 181 i.e. i.e. FW 181 182 , , , 183 188 HIV-1 HIV-1 NNP 189 193 long long JJ 194 202 terminal terminal JJ 203 210 repeats repeat NNS 210 211 ) ) ) 212 215 via via IN 216 227 interaction interaction NN 228 232 with with IN 233 235 an an DT 236 237 E e NN 238 241 box box NN 242 244 on on IN 245 250 their their PRP$ 251 257 target target NN 258 267 promoters promoter NNS 267 268 , , , 269 274 which which WDT 275 277 is be VBZ 278 282 also also RB 283 284 a a DT 285 292 binding bind VBG 293 297 site site NN 298 301 for for IN 302 307 c-Myc c-myc NN 307 308 . . . 309 312 The the DT 313 318 c-Myc c-myc NN 319 330 oncoprotein oncoprotein NN 331 333 is be VBZ 334 343 important important JJ 344 346 in in IN 347 354 control control NN 355 357 of of IN 358 366 cellular cellular JJ 367 380 proliferation proliferation NN 381 384 and and CC 385 400 differentiation differentiation NN 400 401 , , , 402 407 while while IN 408 416 Yin-Yang Yin-Yang NNP 417 418 1 1 CD 419 420 ( ( ( 420 423 YY1 yy1 NN 423 424 ) ) ) 425 428 has have VBZ 429 433 been be VBN 434 439 shown show VBN 440 442 to to TO 443 450 control control VB 451 454 the the DT 455 465 expression expression NN 466 468 of of IN 469 470 a a DT 471 477 number number NN 478 480 of of IN 481 489 cellular cellular JJ 490 493 and and CC 494 499 viral viral JJ 500 505 genes gene NNS 505 506 . . . 507 512 These these DT 513 516 two two CD 517 525 proteins protein NNS 526 536 physically physically RB 537 545 interact interact VBP 546 550 with with IN 551 555 each each DT 556 561 other other JJ 562 565 and and CC 566 574 mutually mutually RB 575 582 inhibit inhibit VBP 583 588 their their PRP$ 589 599 respective respective JJ 600 610 biological biological JJ 611 620 functions function NNS 620 621 . . . 622 624 In in IN 625 629 this this DT 630 635 study study NN 635 636 , , , 637 639 we we PRP 640 644 show show VBP 645 649 that that IN 650 659 USF/c-Myc USF/c-Myc NNP 660 672 up-regulates up-regulate VBZ 672 673 , , , 674 679 while while IN 680 683 YY1 YY1 NNP 684 698 down-regulates down-regulate VBZ 699 702 the the DT 703 711 promoter promoter NN 712 720 activity activity NN 721 723 of of IN 724 729 CXCR4 CXCR4 NNP 729 730 , , , 731 732 a a DT 733 743 coreceptor coreceptor NN 744 747 for for IN 748 749 T t NN 750 761 cell-tropic cell-tropic JJ 762 767 HIV-1 HIV-1 NNP 768 773 entry entry NN 773 774 . . . 775 777 We we PRP 778 782 have have VBP 783 793 identified identify VBN 794 796 an an DT 797 798 E e NN 799 802 box box NN 803 809 around around IN 810 814 -260 -260 CD 815 818 and and CC 819 820 a a DT 821 824 YY1 yy1 NN 825 832 binding binding NN 833 837 site site NN 838 844 around around IN 845 849 -300 -300 CD 850 858 relative relative JJ 859 861 to to TO 862 865 the the DT 866 879 transcription transcription NN 880 885 start start NN 886 890 site site NN 890 891 . . . 892 900 Mutation mutation NN 901 903 of of IN 904 907 the the DT 908 909 E e NN 910 913 box box NN 914 923 abolished abolish VBD 924 934 USF/c-Myc- usf/c-myc- NN 935 943 mediated mediate VBN 944 957 up-regulation up-regulation NN 958 960 of of IN 961 966 CXCR4 cxcr4 NN 967 975 promoter promoter NN 976 984 activity activity NN 984 985 , , , 986 989 and and CC 990 998 mutation mutation NN 999 1001 of of IN 1002 1005 the the DT 1006 1009 YY1 yy1 NN 1010 1017 binding binding NN 1018 1022 site site NN 1023 1026 was be VBD 1027 1037 associated associate VBN 1038 1042 with with IN 1043 1059 unresponsiveness unresponsiveness NN 1060 1062 to to TO 1063 1075 YY1-mediated yy1-mediated JJ 1076 1086 inhibition inhibition NN 1086 1087 . . . 1088 1093 These these DT 1094 1098 data datum NNS 1099 1106 suggest suggest VBP 1107 1111 that that IN 1112 1121 USF/c-Myc USF/c-Myc NNP 1122 1125 and and CC 1126 1129 YY1 YY1 NNP 1130 1133 may may MD 1134 1138 play play VB 1139 1141 an an DT 1142 1151 important important JJ 1152 1156 role role NN 1157 1159 in in IN 1160 1163 the the DT 1164 1181 HIV-1-replicative hiv-1-replicative JJ 1182 1187 cycle cycle NN 1187 1188 , , , 1189 1191 by by IN 1192 1202 modulating modulate VBG 1203 1207 both both CC 1208 1211 the the DT 1212 1217 viral viral JJ 1218 1230 fusion/entry fusion/entry NN 1231 1238 process process NN 1239 1242 and and CC 1243 1248 viral viral JJ 1249 1259 expression expression NN 1259 1260 . . .