Molecular Cloning and Characterization of SRAM, a Novel Insect Rel/Ankyrin-Family Protein Present in Nuclei

Previously, we purified a 59-kDa protein that binds to the κB motif of the Sarcophaga lectin gene. Here we report its cDNA cloning and some of its characteristics as a novel member of the Rel/Ankyrin-family. This protein, named SRAM, contained a Rel homology domain, a nuclear localization signal and 4 ankyrin repeats, but lacked the Ser-rich domain and PEST sequence that Relish contained. We found that SRAM was localized in the nuclei of NIH-Sape-4 cells, which are an embryonic cell line of Sarcophaga. The Sarcophaga lectin gene promoter containing tandem repeats of the κB motifs was activated in NIH-Sape-4 cells. In Drosophila mbn-2 cells, Dif alone activated this reporter gene and a cooperative effect was detected when SHAM and Dif were co-transfected, although SEAM alone did not activate it. This is the first report of a Rel/Ankyrin molecule that exists in the nuclei.