RESUMO
Translin, a highly conserved, DNA/RNA binding protein, is abundantly expressed in brain, testis and in certain malignancies. It was discovered initially in the quest to find proteins that bind to alternating polypurines-polypyrimidines repeats.It has been implicated to have a role in RNA metabolism (tRNA processing, RNAi, RNA transport, etc.), transcription,DNA damage response, etc. Studies from human, mice, drosophila and yeast have revealed that it forms an octameric ring,which is important for its function. Translin is a cytoplasmic protein, but under genotoxic stress, it migrates into thenucleus, binds to the break point hot spots and therefore, thought to be involved in chromosomal translocation events aswell as DNA damage related response. Its structure is known and DNA binding regions, GTP binding region and regionsresponsible for homotypic and heterotypic interaction are known. It forms a ball like structure with open central channel foraccommodating the substrate nucleic acids. Besides this, translin protein binds to 30 and 50 UTR of certain mRNAs andprobably regulates their availability for translation. It is also involved in mRNA transport and cell cycle progression. Itforms a heteromeric complex with translin associated factor-X (TRAX) to form C3PO complex which is involved in RNAsilencing process. Recently, it has been shown that translin is upregulated under starvation conditions in Drosophila and isinvolved in the integration of sleep and metabolic rate of the flies. Earlier studies classified translin as a DNA repair protein;however subsequent studies showed that it is a multifunctional protein. With this background, in this review we havesummarized the translin biochemical activities, cellular function as well as structural properties of this important protein.
RESUMO
Recombinases are known to play an important role in the homology search and strand exchange during meiosis as well as homologous recombination (HR)-mediated DNA repair specifically require Mg2+ ion for their activity. The Ca2+ has been shown to stimulate the strand exchange activity of hDmc1 and ScDmc1 by forming the extended filaments on DNA. Oryza sativa disrupted meiotic cDNA1A (OsDmc1A), a homologue of yeast and human Dmc1 from rice shows the hallmark functions of recombinase. Here, we report the effects of Ca2+ and Mg2+ on OsDmc1A activity from rice (Oryza sativa). OsDmc1A showed a concentration-dependent binding with both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) substrates in presence of Mg2+ or Ca2+. The ssDNA and dsDNA binding activities, as well as renaturation activity of OsDmc1A were similar in the presence of Ca2+ or Mg2+. Increasing the Ca2+ or Mg2+ increased the DNA binding, renaturation and strand exchange of OsDmc1A. But, OsDmc1A showed only a slight stimulation of strand exchange activity in presence of Ca2+, when compared the activity in presence of Mg2+. Electron microscopy showed that OsDmc1A formed ring-like structures in presence of Mg2+ or Ca2+. However, OsDmc1A formed filament like structures with both ss and dsDNA in presence of Mg2+ or Ca2+. Taken together, Ca2+ did not affect OsDmc1A recombinase activity significantly.