Identification of a putative regulator of early-histone gene expression of Paracentrotus lividus

Drosophila GAGA factor (GAF) is a nuclear protein, conserved along evolution, with multiple roles in gene regulation, chromatin remodelling, Polycomb-dependent silencing, and insulator functions (1). GAF recognizes and specifically binds GAGAG consensus DNA motif by its C2H2-type zinc-finger domain, and interacts with other regulatory factors by its BTB/POZ domain. We have identified plGaga, a cDNA coding for a putative GAF of the sea urchin P. lividus, which showed significant sequence similarity with Drosophila and vertebrate GAFs. Real time RT-PCR revealed that the plGaga RNA is always present during embryo development decreasing rapidly in abundance at the larval pluteus stage. We raised a specific antibody against the sea urchin GAF and used it in whole-mount immunofluorescence assays, showing that the protein was distributed predominantly to the nuclei of the whole embryo. By Chromatin Immunoprecipitation experiments, we showed that the sea urchin GAF not only binds the sns5 insulator, which is essential for the regulation of the sea urchin early-histone genes (2,3), but also to other GAGA containing sequences in the early-histone gene cluster. 1 Matharu NK et al. 2010 JMB 400 (3): 434–447 2 Melfi R et Al. 2001 JMB (1); 304:753-63 3 Cavalieri V et al. 2013 Nucleic Acids Res 37: 7407-7415