User:Linguard/sandbox

The Z box is made of 2 different sequences(Za & Zb) in the insulin gene.

The Z box behaves as an enhancer for the transcription of insulin gene in fetal and mature primary islet cells. However, it acts as a repressor for all other cells including immortalized beta cells and beta tumor cells. The deletion of the Z box sequence from the insulin gene of primary islet cells results in a decreased insulin production while similar deletions in other cells increases insulin production.