Zic1 is a transcriptional repressor through the lamin A/C promoter and has an intrinsic repressive domain

Zic family proteins are expressed in the cerebellum and play important roles in vertebrate development. However, very few observations have been made regarding the function of Zic proteins in transcription. We previously showed, using P19 cells as a model system, that the lamin A/C promoter has a retinoic acid responsive element (L-RARE), and that Sp1 and Sp3 bind the CACCC box of the L-RARE. Here, Zic1 is identified as a binding protein of the L-RARE by yeast one-hybrid screening. We show that Zic1 can bind to and repress transcription through the CACCC box of the L-RARE. Moreover, reporter assays using various fusion proteins of Zic1 with the GAL4 DNA binding domain reveal that Zic1 has an intrinsic transcriptional repressive and activation domain.