Figure S1 A B C * * * * * * * * * * * * * * * * * * * * * * * * * * * Mi-2 081 Mi-2 081 Mi-2 081 * * * * * * * * * * * * * * * * * * * Fraction of inputt * * * * Fraction of inputt * * * Fraction of inputt * Mi-2 082 Mi-2 082 Mi-2 082 * * * * * * * * * * * * * * * * * * * * Fraction of inputt * * Fraction of inputt * * * * Fraction of inputt * *

Figure S2 A B C D * * * * * * * * * * * * * * * * * * * * * * * * * * Fraction of inputt * * * * * * * * * * * C D * * * * * * * * * * Fraction of inputt * * *

Figure S3 fetal liver megakaryocytes * * * * * * * * 0.01 0.02 0.03 0.04 0.05 0.06 0.07 * * * * * * Fraction of inputt gIgG MTA2 RbAp46 Ib Mpl Gp9 Gp1b Pf4 neg. Ctr Hbb-b1 pro

Figure S4 A  B  % activity 5% input triple mut GST K5A WT   MTA-1  MTA-2  RbAp48 RbAp46  Coomassie B 140 120 100 % activity 80 60 40 20 GAL4 WT K5A triple mut

Figure S5 (-) Fold Activation 70 P=0.06 None GATA-1 FOG-1 GATA-1/FOG-1 60 50 40 Fold Activation 30 20 10 (-) mock siRNA ctr1 siRNA/MTA

Figure S6 A B Ctr. Agouti mice 1 2 3 4 5 6 8 7 9 10 M 13.5kb 11.4kb WT Locus Targeting Vector HSV-TK 5’ Arm, 12kb 3’ Arm, 5kb FRT exon 2 MSRRKQSNPRQIK neo probe exon 1 EcoRV 13.5kb 11.4kb R3GR4GK5A (Sac1) MSGGAQSNPRQIK Targeted neo excised Locus A Ctr. Agouti mice 1 2 3 4 5 6 8 7 B 9 10 M 13.5kb 11.4kb

Figure S6 C D E MK Ery Ery FOG-1 ß-actin +/+ ki/ki +/+ ki/ki +/+ ki/ki wt targeted neo excised PCR products: 208bp > 2kb 278bp C 278bp 208bp D 1 2 3 4 5 6 8 7 100 200 300 400 500 600 M Mice from +/ki and +/ki crosses E MK Ery Ery FOG-1 ß-actin +/+ ki/ki +/+ ki/ki +/+ ki/ki FOG-1 FOG-1 ß-actin ß-actin