Dimerization of the DEAD-Box Cyanobacterial RNA Helicase Redox, CrhR

Abstract

The DEAD-box cyanobacterial RNA helicase redox, or CrhR, in Synechocystis sp. PCC 6803 is capable of unwinding dsRNA and in annealing ssRNA in a bidirectional ATP-dependent manner. This is a feature shared by only four other DEAD-box RNA helicases. Two of which, the eukaryotic p68 and p72 proteins, were also shown to self-dimerize. Self-dimerization is a characteristic rarely possessed by an RNA helicase. In this study, CrhR was found to exhibit self-interaction using the yeast two-hybrid system and differentially tagged-CrhR protein exchange (swap) analysis, with the dimerization domain localized to the N-terminus, and some assistance, or partial dimerization occurring through the C-terminus. FPLC analysis also revealed CrhR dimerization to occur in an RNA-independent manner. In addition to FPLC analysis, mass spectrometry also suggests CrhR interaction with protein complexes in vivo. These findings suggest physiological functions for CrhR association with ribosomes in multi-subunit complexes upon acclimatization of Synechocystis cells to low temperature.