TAL1 and acute lymphoblastic leukemia: When we examine the interaction between the TAL1 promoter-IV and +19 enhancer in a TAL1-negative primary T-ALL patient sample (08H028) and a TAL1-positive patient sample (08H125), the TAL1 promoter-IV only weakly interacts with the +19 enhancer in the TAL1-negative patient (08H028) (Figure 3B).