Date Published: March 4, 2014
Publisher: Public Library of Science
Author(s): Yu-Yuan Hsiao, Woei-Horng Fang, Chia-Chia Lee, Yi-Ping Chen, Hanna S. Yuan, Gregory A. Petsko
Abstract: Structure analysis of the exonuclease RNase T reveals that it also functions in DNA repair pathways where it binds and processes bulge, bubble, and Y-structured DNA to trim the DNA 3′ ends.
Partial Text: It is well known that DNA repair mechanisms maintain genomic integrity and are essential for cell survival. Damaged DNA can be restored by a variety of DNA repair processes, such as direct reversal, base excision, nucleotide excision, mismatch, and recombination repair pathways . Although diverse proteins play different roles in these pathways, DNA repair is generally accomplished by a coordinated effort via several types of DNA enzymes, including endonucleases that nick DNA near the damaged site, exonucleases that trim DNA from the broken end, helicases that unwind duplex DNA, polymerases that make new strand DNA with correct sequences, and ligases that seal the restored DNA strands. Among all these DNA enzymes, the molecular functions of exonucleases, which bind at the 3′ or 5′ end of DNA and cleave one nucleotide at a time, are least understood. How they select, rather than randomly bind to, a broken end of DNA and process it up to the site for the next-step processing remains to be investigated.