Identification of the reaction products of (2′‐5′)oligoadenylate synthetase in the marine sponge

Abstract

Previously we reported on the presence of a high (2′-5′)oligoadenylate synthetase activity in the marine sponge Geodia cydonium [Kuusksalu, A., Pihlak, A., Müller, W. E. G. & Kelve, M. (1995) Eur. J. Biochem. 232, 351Ϫ357]. The presence of (2′-5′)oligoadenylates [(2′-5′)A] in crude sponge extract was shown by radioimmunoassay and by their HPLC comigration with authentic (2′-5′)A oligomers. In addition, the sponge (2′-5′)oligoadenylates displayed biological activity, as determined by inhibition studies of protein biosynthesis in rabbit reticulocyte lysate. In the present study individual (2′-5′)oligoadenylates synthesized by sponge enzyme were separated by HPLC. The exact composition of every oligonucleotide peak eluted was determined by matrix-assisted laser-desorption-ionization mass spectrometry (MALDI-MS) analysis. The 2′-5′ phosphodiester bond in oligoadenylates was verified by NMR analysis. Based on the high concentration of (2′-5′)A oligomers in G. cydonium and their similarity with those found in mammals we propose that the (2′-5′)A system is involved in a cytokine-mediated pathway and/ or in a protection system against viruses, present in the marine environment.Keywords : (2′-5′)oligoadenylate; Geodia cydonium ; matrix-assisted laser-desorption-ionization MS; NMR.Sponges (Porifera) are the simplest multicellular animals, which have existed since the Proteozoic period [1]. In the past few years several cDNA/gene sequences have been isolated and characterized from sponges, especially from the marine demosponge Geodia cydonium. Analyses revealed that sponges contain proteins of the extracellular matrix/basal lamina (e.g. integrin receptor [2], collagen [3] or galectin [4,5]), cell-surface receptors (tyrosine kinase receptor [6]), elements of the sensory system (crystallin [7], metabotropic glutamate receptor [8]) and homologs/modules of an immune system (immunoglobulin-like domains [9], scavenger receptor cysteine-rich domains and short consensus repeats [10], Rh-like protein [11]). These molecules were found to display high similarity to sequences from members of higher metazoan phyla [12].Recently a cDNA encoding a putative cytokine, the endothelial monocyte-activating polypeptide [13], was identified in G. cydonium [14]. The physiological role of this factor in sponges is not known. One pathway in mammalian organisms which is controlled by cytokine(s) is the (2′-5′)oligoadenylate [2′-5′(A)] system. It regulates the RNA degradation pathway and is inCorrespondence to M. Kelve,

Sponge OAS has a distinct genomic structure within the 2-5A synthetase family

“…We have demonstrated the presence of OAS in the evolutionarily lowest multicellular animals, sponges (Kuusksalu et al 1995(Kuusksalu et al , 1998. As sponges reside close to the metazoan stem, their genomic analysis will give us an insight into the ancient genomic conditions from which metazoan emerged.…”

Gene structure and function of the 2′-5′-oligoadenylate synthetase family

“…The differences between the two sequences are found in the 3% region, which might correspond to the terminal exon, where a 100-nt sequence in clone A has been replaced by 3 nt in clone B. PCR amplifications using chicken erythrocyte DNA indicate that the two cDNA clones represent alleles of an OAS gene. Furthermore, the PCR analysis revealed the presence of a small intron with the 5% end corresponding to the terminus of human exon E. The marine sponge G. cydonium possesses a high level of OAS activity [79] and by radioimmunoassay and high-performance liquid chromatography, OASs were demonstrated to be present in the sponge [80]. A potential OAS cDNA clone was recently isolated from G. cydonium [16]; it encodes a protein of 327 amino acids with some but limited homology to human OAS1 ( fig.…”

Expressed 2–5A synthetase genes and pseudogenes in the marine sponge Geodia barretti

“…The presence of 2-5A synthetases is still not limited to mammals. The OAS has been found even in the evolutionarily oldest extant metazoans, sponges (Kuusksalu et al, 1995(Kuusksalu et al, , 1998Wiens et al, 1999). An extensive genomic analysis has revealed the ancient origin of the OAS gene family; they have been identified throughout the metazoan phylogeny (Torralba et al, 2008) and even in a closely related sister group of metazoan, choanoflagellates (Kjaer et al, 2009).…”