RNA melting and RNA chaperone activities of plant cold shock domain proteins are not correlated

Cold shock domain proteins (CSDPs) participate in plant development and resistance, but the underlying molecular mechanisms are poorly understood. In this study, we demonstrated that the CSDPs, including EsCSDP1, EsCSDP2, and EsCSDP3, from the extremophyte Eutrema salsugineum possess all basic properties of RNA chaperones. EsCSDP1-3 melt secondary structures in RNAs with various nucleotide sequences and exhibit RNA chaperone activity in vitro. EsCSDP1 and EsCSDP3 were shown to have higher RNA melting activity, whereasile EsCSDP2 had higher RNA chaperone activity. We demonstrated that higher RNA melting activity correlates with the longer C-terminal fragment in many zinc finger motifs, whereas increased RNA chaperone activity was most likely due to the higher glycine content and RGG repeat number in the C-terminal fragment.