0 10 Modulation modulation NN 11 13 of of IN 14 17 E2F E2F NNP 18 27 complexes complex NNS 28 34 during during IN 35 37 G0 g0 NN 38 40 to to TO 41 42 S S NNP 43 48 phase phase NN 49 59 transition transition NN 60 62 in in IN 63 68 human human JJ 69 76 primary primary JJ 77 90 B-lymphocytes b-lymphocyte NNS 90 91 . . . 93 96 The the DT 97 103 pocket pocket NN 104 115 protein-E2F protein-e2f JJ 116 125 complexes complex NNS 126 129 are be VBP 130 141 convergence convergence NN 142 148 points point NNS 149 152 for for IN 153 157 cell cell NN 158 163 cycle cycle NN 164 173 signaling signaling NN 173 174 . . . 175 177 In in IN 178 181 the the DT 182 189 present present JJ 190 196 report report NN 196 197 , , , 198 200 we we PRP 201 211 identified identify VBD 212 215 and and CC 216 225 monitored monitor VBD 226 229 the the DT 230 236 pocket pocket NN 237 248 protein-E2F protein-e2f NN 249 258 complexes complex NNS 259 261 in in IN 262 267 human human JJ 268 275 primary primary JJ 276 289 B-lymphocytes b-lymphocyte NNS 290 295 after after IN 296 306 activation activation NN 307 309 by by IN 310 317 phorbol phorbol NN 318 330 12-myristate 12-myristate NN 331 341 13-acetate 13-acetate NN 341 342 . . . 343 353 Consistent consistent JJ 354 358 with with IN 359 367 previous previous JJ 368 372 data datum NNS 373 377 from from IN 378 383 human human JJ 384 387 and and CC 388 393 mouse mouse NN 394 405 fibroblasts fibroblast NNS 406 409 and and CC 410 423 T-lymphocytes t-lymphocyte NNS 423 424 , , , 425 429 E2F4 e2f4 NN 430 433 and and CC 434 437 DP1 dp1 NN 438 442 form form VBP 443 446 the the DT 447 458 predominant predominant JJ 459 462 E2F e2f NN 463 475 heterodimers heterodimer NNS 476 480 both both CC 481 483 in in IN 484 486 G0 G0 NNP 487 490 and and CC 491 493 G1 g1 NN 494 500 phases phase NNS 501 503 of of IN 504 507 the the DT 508 513 human human JJ 514 526 B-lymphocyte B-lymphocyte NNP 527 531 cell cell NN 532 537 cycle cycle NN 537 538 , , , 539 546 whereas whereas IN 547 551 E2F1 E2F1 NNP 552 555 and and CC 556 558 -3 -3 CD 559 562 are be VBP 563 568 first first RB 569 577 detected detect VBN 578 580 in in IN 581 585 late late JJ 586 588 G1 g1 NN 588 589 , , , 590 593 and and CC 594 599 their their PRP$ 600 610 expression expression NN 611 617 levels level NNS 618 626 increase increase VBP 627 634 towards towards IN 635 636 S S NNP 637 642 phase phase NN 642 643 . . . 644 656 Intriguingly intriguingly RB 656 657 , , , 658 661 the the DT 662 667 major major JJ 668 671 E2F e2f NN 672 679 complex complex NN 680 684 that that WDT 685 687 we we PRP 688 696 detected detect VBD 697 699 in in IN 700 709 quiescent quiescent JJ 710 715 human human JJ 716 729 B-lymphocytes b-lymphocyte NNS 730 732 is be VBZ 733 742 consisted consist VBN 743 745 of of IN 746 749 pRB pRB NNP 749 750 , , , 751 755 E2F4 E2F4 NNP 755 756 , , , 757 760 and and CC 761 764 DP1 DP1 NNP 764 765 . . . 766 772 Though though IN 773 776 the the DT 777 783 levels level NNS 784 786 of of IN 787 790 DP1 DP1 NNP 791 794 and and CC 795 797 -2 -2 CD 798 806 increase increase VBP 807 811 when when WRB 812 817 cells cell NNS 818 826 progress progress VBP 827 831 from from IN 832 834 G0 g0 NN 835 837 to to TO 838 839 S S NNP 839 840 , , , 841 844 the the DT 845 855 proportion proportion NN 856 858 of of IN 859 862 DP1 dp1 NN 863 865 to to TO 866 869 DP2 dp2 NN 870 877 remains remain VBZ 878 888 relatively relatively RB 889 897 constant constant JJ 898 904 during during IN 905 908 the the DT 909 913 cell cell NN 914 919 cycle cycle NN 919 920 . . . 921 923 We we PRP 924 928 also also RB 929 937 observed observe VBD 938 940 an an DT 941 949 increase increase NN 950 952 in in IN 953 968 electrophoretic electrophoretic JJ 969 977 mobility mobility NN 978 980 of of IN 981 984 the the DT 985 996 predominant predominant JJ 997 1000 E2F e2f NN 1001 1011 components component NNS 1011 1012 , , , 1013 1016 DP1 DP1 NNP 1017 1020 and and CC 1021 1025 E2F4 E2F4 NNP 1025 1026 , , , 1027 1029 as as IN 1030 1043 B-lymphocytes b-lymphocyte NNS 1044 1054 progressed progress VBN 1055 1059 from from IN 1060 1062 G0 g0 NN 1063 1067 into into IN 1068 1073 early early JJ 1074 1076 G1 g1 NN 1076 1077 . . . 1078 1082 This this DT 1083 1091 increase increase NN 1092 1094 in in IN 1095 1103 mobility mobility NN 1104 1107 was be VBD 1108 1120 attributable attributable JJ 1121 1123 to to TO 1124 1141 dephosphorylation dephosphorylation NN 1141 1142 , , , 1143 1145 as as IN 1146 1152 lambda lambda NN 1153 1164 phosphatase phosphatase NN 1165 1174 treatment treatment NN 1175 1180 could could MD 1181 1188 convert convert VB 1189 1192 the the DT 1193 1199 slower slow JJR 1200 1209 migrating migrating JJ 1210 1215 forms form NNS 1216 1220 into into IN 1221 1224 the the DT 1225 1238 corresponding correspond VBG 1239 1245 faster fast JJR 1246 1254 mobility mobility NN 1255 1260 forms form NNS 1260 1261 . . . 1262 1264 We we PRP 1265 1272 further further RB 1273 1285 demonstrated demonstrate VBD 1286 1290 that that IN 1291 1295 this this DT 1296 1302 change change NN 1303 1305 in in IN 1306 1321 phosphorylation phosphorylation NN 1322 1328 status status NN 1329 1339 correlates correlate VBZ 1340 1344 with with IN 1345 1346 a a DT 1347 1355 decrease decrease NN 1356 1358 in in IN 1359 1362 DNA DNA NNP 1363 1370 binding binding NN 1371 1379 activity activity NN 1379 1380 . . . 1381 1385 This this DT 1386 1396 modulation modulation NN 1397 1399 of of IN 1400 1403 DNA DNA NNP 1404 1411 binding binding NN 1412 1420 activity activity NN 1421 1429 mediated mediate VBN 1430 1437 through through IN 1438 1441 the the DT 1442 1459 dephosphorylation dephosphorylation NN 1460 1462 of of IN 1463 1466 DP1 DP1 NNP 1467 1470 and and CC 1471 1475 E2F4 E2F4 NNP 1476 1481 could could MD 1482 1486 help help VB 1487 1489 to to TO 1490 1497 explain explain VB 1498 1501 the the DT 1502 1506 lack lack NN 1507 1509 of of IN 1510 1512 in in FW 1513 1517 vivo vivo FW 1518 1521 DNA dna NN 1522 1534 footprinting footprinting NN 1535 1537 in in IN 1538 1542 late late JJ 1543 1545 G1 G1 NNP 1546 1549 and and CC 1550 1551 S S NNP 1552 1558 phases phase NNS 1559 1561 of of IN 1562 1566 gene gene NN 1567 1576 promoters promoter NNS 1577 1587 negatively negatively RB 1588 1597 regulated regulate VBN 1598 1605 through through IN 1606 1609 E2F E2F NNP 1610 1615 sites site NNS 1616 1619 and and CC 1620 1628 suggests suggest VBZ 1629 1630 a a DT 1631 1636 novel novel JJ 1637 1646 mechanism mechanism NN 1647 1650 for for IN 1651 1662 controlling control VBG 1663 1666 E2F E2F NNP 1667 1682 transcriptional transcriptional JJ 1683 1691 activity activity NN 1692 1698 during during IN 1699 1702 the the DT 1703 1713 transition transition NN 1714 1718 from from IN 1719 1729 quiescence quiescence NN 1730 1732 to to TO 1733 1746 proliferation proliferation NN 1746 1747 . . .