Figure 8. Effects of the MITF isoforms A and M are comparable. A: Full-length (FL) MITF isoforms A and M and their known domains are shown with the corresponding amino acids: MITF-A domains A, B1b, and AD, common domains bHLH-LZ and S, and the MITF-M specific N-terminal region (M). Additional six amino acids of the M isoform (aa187–192) are shown. B: Interactions of the full-length OTX2 and domains from the MITF isoform A (FL: aa1–520; A-B1b-AD: aa1–297) or M (FL: aa1–419; M-AD: aa1–196) were measured and are shown with gray columns. The level of MITF auto-activation is indicated by white columns. Assays were performed as in Figure 7 from three independent experiments each performed in quadruplicate. C: ARPE-19 cells were cotransfected with the proximal TYR promoter lacking any OTX2 sites but with intact (−152: black columns) or mutated MITF binding sites (−152mMmE: gray columns). Normalized luciferase activities are relative to TYR promoter construct −152 (=1) cotransfected with the empty expression vector pCR3 (=no TF). Data are means±SEM from two independent transfections each performed in triplicate.