Sponge non-metastatic Group I Nme gene/protein - structure and function is conserved from sponges to humans

Abstract

BackgroundNucleoside diphosphate kinases NDPK are evolutionarily conserved enzymes present in Bacteria, Archaea and Eukarya, with human Nme1 the most studied representative of the family and the first identified metastasis suppressor. Sponges (Porifera) are simple metazoans without tissues, closest to the common ancestor of all animals. They changed little during evolution and probably provide the best insight into the metazoan ancestor's genomic features. Recent studies show that sponges have a wide repertoire of genes many of which are involved in diseases in more complex metazoans. The original function of those genes and the way it has evolved in the animal lineage is largely unknown. Here we report new results on the metastasis suppressor gene/protein homolog from the marine sponge Suberites domuncula, NmeGp1Sd. The purpose of this study was to investigate the properties of the sponge Group I Nme gene and protein, and compare it to its human homolog in order to elucidate the evolution of the structure and function of Nme.ResultsWe found that sponge genes coding for Group I Nme protein are intron-rich. Furthermore, we discovered that the sponge NmeGp1Sd protein has a similar level of kinase activity as its human homolog Nme1, does not cleave negatively supercoiled DNA and shows nonspecific DNA-binding activity. The sponge NmeGp1Sd forms a hexamer, like human Nme1, and all other eukaryotic Nme proteins. NmeGp1Sd interacts with human Nme1 in human cells and exhibits the same subcellular localization. Stable clones expressing sponge NmeGp1Sd inhibited the migratory potential of CAL 27 cells, as already reported for human Nme1, which suggests that Nme's function in migratory processes was engaged long before the composition of true tissues.ConclusionsThis study suggests that the ancestor of all animals possessed a NmeGp1 protein with properties and functions similar to evolutionarily recent versions of the protein, even before the appearance of true tissues and the origin of tumors and metastasis.

Characterization of a group I Nme protein of Capsaspora owczarzaki—a close unicellular relative of animals

“…Comparison with the previous study of a group I Nme protein from a sponge, a simple non-bilaterian animal, 7 and research on mammalian (mostly human) group I Nme proteins provide a better insight into changes that occurred in transition to multicellularity and subsequently in the animal lineage.…”

“…Human Nme1 did not display the ability to bind sscDNA, while human Nme2 binds sscDNA. 7 Nme2 is involved in DNA structural changes necessary for the activity of the c-myc promoter. It binds to the NHE sequence of the c-myc promoter cloned into pUC19, which yields mostly nicked circular plasmid.…”

“…7 Recombinant plasmid pUC19-NHE (50 ng) and empty pUC19 was incubated with NmeGp1Co protein as indicated (Figure 4). The reaction was assembled in 50 mM KCl, 10 mM MgCl 2 , 50 mM Tris-HCl (pH 7.5), 0.5 mM DTT, and 30 μg/ml BSA, and incubated 30 min at 37°C.…”

“…Moreover, we found that the sponge Nme1 (NmeGp1Sd) is recognized by human cells as their own protein, and is able to diminish migratory (metastatic) potential of cancer cells. 7 So far the work on Nme1 in unicellular eukaryotes has been very limited with no data available on the properties of Nme homologs in close unicellular relatives of animals. Herein, we present a study of a group I Nme protein from Capsaspora owczarzaki-a close unicellular relative of animals.…”

“…Human Nme2 is highly homologous to human Nme1, but has different pI value. 7 These two proteins form enzymatically active heteroor homohexamer in any possible combination of subunits (6Nme1, 5Nme1+1Nme2,… 6Nme2). Besides diphosphate kinase activity, Nme1 and Nme2 also act as histidine kinases, 8,9 3′-5′ exonucleases, 10 and transcriptional regulators.…”