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 generegulation, chromatin remodelling, Polycomb-dependent silencing, and insulator functions (1). GAFrecognizes and specifically binds GAGAG consensus DNA motif by its C2H2-type zinc-finger domain, andinteracts with other regulatory factors by its BTB/POZ domain. We have identified plGaga, a cDNA codingfor a putative GAF of the sea urchin P. lividus, which showed significant sequence similarity withDrosophila and vertebrate GAFs. Real time RT-PCR revealed that the plGaga RNA is always present duringembryo development decreasing rapidly in abundance at the larval pluteus stage. We raised a specificantibody against the sea urchin GAF and used it in whole-mount immunofluorescence assays, showing thatthe protein was distributed predominantly to the nuclei of the whole embryo. By ChromatinImmunoprecipitation 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 GAGAcontaining sequences in the early-histone gene cluster.1 Matharu NK et al. 2010 JMB 400 (3): 434–4472 Melfi R et Al. 2001 JMB (1); 304:753-633 Cavalieri V et al. 2013 Nucleic Acids Res 37: 7407-7415