Effect of a large deletion of the basic domain of mitranscription factor on differentiation of mast cells

Abstract
The mi transcription factor (MITF) is a basic-helix-loop-helix-leucine zipper transcription factor that is important for the development of mast cells. Cultured mast cells (CMCs) of mi/mi genotype express abnormal MITF (mi-MITF), but CMCs of tg/tg genotype do not express any MITFs. It was previously reported thatmi/mi CMCs showed more severe abnormalities thantg/tg CMCs, indicating that mi-MITF had inhibitory function. Whereas mi-MITF contains a single amino acid deletion in the basic domain, MITF encoded bymiewallele (ew-MITF) deletes 16 of 21 amino acids of the basic domain. Here the effect of a large deletion of the basic domain was examined. Inmiew/miew CMCs, the expression pattern of genes whose transcription was affected by MITF was comparable to that of tg/tg CMCs rather than to that ofmi/mi CMCs. This suggested that ew-MITF lacked any functions. The part of the basic domain deleted inew-MITF appeared necessary for either transactivation or inhibition of transactivation.