EXPRESSION OF THE POTENTIAL BIOMARKER HEAT-SHOCK-PROTEIN-70 AND ITS REGULATOR, THE METAZOAN DNAJ HOMOLOG, BY TEMPERATURE STRESS IN THE SPONGE GEODIA-CYDONIUM

Because sponges (Porifera) are generally the dominant group of multice llular animals found in the marine benthos they are key animals for th e testing of biomarkers in this biotope. Previously, it was shown that the heat shock protein hsp70 from the marine sponge Geodia cydonium i s a useful biomarker for following biological responses to selected ph ysical and chemical stressors. One protein which is critical for hsp70 function in other organisms is the DnaJ-like protein. In this study w e therefore isolated and characterized a cDNA encoding the DnaJ-like p rotein from G, cydonium designated GCDNAJ. GCDNAJ is 1476 base pairs ( bp) long with a 1236 bp open reading frame encoding a protein of 45 54 2 daltons. Northern blot analysis revealed a transcript size of 1.5 ki lobase (kb). The deduced amino acid (aa) sequence of GCDNAJ contains m otifs characteristic of most prokaryotic and eukaryotic DnaJ family me mbers. In response to a 7 degrees C temperature increase, expression o f the transcripts encoding hsp70 and DnaJ-like protein increased as mu ch as 18-fold and 3-fold, respectively, within a 8 h period. From thes e data we conclude that the levels of both hsp70 and DnaJ-like protein are likely to be important to the adaptation to temperature increases in G. cydonium.