Small Drosophila zinc finger C2H2 protein with an N-terminal zinc finger-associated domain demonstrates the architecture functions.

Recently, the concept has arisen that a special class of architectural proteins exists, which are responsible not only for global chromosome architecture but also for the local regulation of enhancer-promoter interactions. Here, we describe a new architectural protein, with a total size of only 375 aa, which contains an N-terminal zinc finger-associated domain (ZAD) and a cluster of five zinc finger C2H2 domains at the C-terminus. This new protein, named ZAD and Architectural Function 1 protein (ZAF1 protein), is weakly and ubiquitously expressed, with the highest expression levels observed in oocytes and embryos. The cluster of C2H2 domains recognizes a specific 15-bp consensus site, located predominantly in promoters, near transcription start sites. The expression of ZAF1 by a tissue-specific promoter led to the complete blocking of the eye enhancer when clusters of ZAF1 binding sites flanked the eye enhancer in transgenic lines, suggesting that the loop formed by the ZAF1 protein leads to insulation. The ZAF1 protein also supported long-range interactions between the yeast GAL4 activator and the white promoter in transgenic Drosophila lines. A mutant protein lacking the ZAD failed to block the eye enhancer or to support distance interactions in transgenic lines. Taken together, these results suggest that ZAF1 is a minimal architectural protein that can be used to create a convenient model for studying the mechanisms of distance interactions.