Previous Evidence of Regulation

Before this study, few targets of TAL1 had been identified in the different hematopoietic lineages, and only four of them in the context of T-cell leukemia. The complete list of previously identified targets for TAL1 is listed in the table below.

We have not detected significant binding of TAL1 to these promoters using our p<0.001 cutoff. Some of these genes may correspond to false negatives in our ChIP on chip analysis, however most of the targets previously described for TAL1 were identified in hematopoietic lineages different from thymocytes or leukemic T-cells and may not be accessible for TAL1 binding in the chromatin context of T-ALL. In the case of RALDH2, pT and CD4, these promoters are bound by TAL1 in intronic sequences (RALDH2) or in enhancers (pT and CD4) respectively, which are not present in the Hu13K array. In support of this explanation, we detected TAL1 binding to the intronic sequences that drive the expression of