A Novel Cold-Regulated Cold Shock Domain Containing Protein from Scallop Chlamys farreri with Nucleic Acid-Binding Activity

BACKGROUND: The cold shock domain (CSD) containing proteins (CSDPs) are one group of the evolutionarily conserved nucleic acid-binding proteins widely distributed in bacteria, plants, animals, and involved in various cellular processes, including adaptation to low temperature, cellular growth, nutrient stress and stationary phase. METHODOLOGY: The cDNA of a novel CSDP was cloned from Zhikong scallop Chlamys farreri (designated as CfCSP) by expressed sequence tag (EST) analysis and rapid amplification of cDNA ends (RACE) approach. The full length cDNA of CfCSP was of 1735 bp containing a 927 bp open reading frame which encoded an N-terminal CSD with conserved nucleic acids binding motif and a C-terminal domain with four Arg-Gly-Gly (RGG) repeats. The CSD of CfCSP shared high homology with the CSDs from other CSDPs in vertebrate, invertebrate and bacteria. The mRNA transcripts of CfCSP were mainly detected in the tissue of adductor and also marginally detectable in gill, hepatopancreas, hemocytes, kidney, mantle and gonad of healthy scallop. The relative expression level of CfCSP was up-regulated significantly in adductor and hemocytes at 1 h and 24 h respectively after low temperature treatment (P<0.05). The recombinant CfCSP protein (rCfCSP) could bind ssDNA and in vitro transcribed mRNA, but it could not bind dsDNA. BX04, a cold sensitive Escherichia coli CSP quadruple-deletion mutant, was used to examine the cold adaptation ability of CfCSP. After incubation at 17°C for 120 h, the strain of BX04 containing the vector pINIII showed growth defect and failed to form colonies, while strain containing pINIII-CSPA or pINIII-CfCSP grew vigorously, indicating that CfCSP shared a similar function with E. coli CSPs for the cold adaptation. CONCLUSIONS: These results suggest that CfCSP is a novel eukaryotic cold-regulated nucleic acid-binding protein and may function as an RNA chaperone in vivo during the cold adaptation process.