Class II transactivator suppresses transcription of thyroid-specific genes

Class II transactivator (CIITA) is the master regulator of MHC class II gen es, and mediates their induction by interferon gamma (IFN gamma). To study the role of CIITA in modulating the expression of thyroid-specific genes, w e cloned the full-length rat CIITA and use it to transfect a rat thyroid ce ll line. We found that only one type of CIITA, type TV, is induced in thyro id cells upon IFN gamma stimulation, and that CIITA is capable not only of inducing the expression of MHC genes in the thyroid, but also of differenti ally suppressing the expression of thyroid-specific genes. These findings s uggest new avenues for the development of thyroid autoimmune diseases. (C) 2000 Academic Press.