Characterization of a plant (rice) translin and its comparative analysis with human translin.

ABSTRACT

MAIN CONCLUSION: For the first time, a plant (rice) translin was characterized. The rice translin protein, which was octameric in native state, bound efficiently to single-stranded DNA and RNA. Translin, a DNA-/RNA-binding protein, is expressed in brain, testis and in certain malignancies. It is involved in chromosomal translocation, mRNA metabolism, transcriptional regulation and telomere protection. Studies from human, mice, drosophila and yeast have revealed that it forms an octameric ring, which is important for its function. In spite of the absence of neuronal functions and cancer processes, translin is present in plant systems, but information on plant translin is lacking. Here we report the characterization of a plant (rice) translin. Translin cDNA from O. sativa was cloned into an expression vector; protein was over-expressed in E. coli and subsequently purified to homogeneity. Circular dichroism and homology-based modeling showed that the rice translin protein was similar to the other translin proteins. Native PAGE and gel-filtration analyses showed rice translin to form an octamer and this octameric assembly was independent of disulphide bonds. Rice translin bound to single-stranded DNA sequences like human translin, but not to the double-stranded DNA. Rice translin bound more efficiently to linear DNA (with staggered ends) than open or closed circular DNA. Rice translin also bound to RNA, like its human counterpart. Rice translin displays all the characteristic properties of the translin group of proteins and does indeed qualify as a bonafide "translin" protein. To our knowledge, this is the first report wherein the translin protein from a plant source has been functionally characterized. Understanding the translin biology from plant systems will give the new insights into its functional role during plant development.