한빛사논문
Hyunjee Lee1,2,3, HyeokJin Cho1,2,3, Jooyoung Kim1, Sua Lee1, Jungmin Yoo1,2,3, Daeho Park1,3 and Gwangrog Lee1,2,3,*
1School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Korea, 2Single-Molecule Biology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea and 3Cell Mechanobiology Laboratory, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
*To whom correspondence should be addressed.
Abstract
RNase H is involved in fundamental cellular processes and is responsible for removing the short stretch of RNA from Okazaki fragments and the long stretch of RNA from R-loops. Defects in RNase H lead to embryo lethality in mice and Aicardi-Goutieres syndrome in humans, suggesting the importance of RNase H. To date, RNase H is known to be a non-sequence-specific endonuclease, but it is not known whether it performs other functions on the structural variants of RNA:DNA hybrids. Here, we used Escherichia coli RNase H as a model, and examined its catalytic mechanism and its substrate recognition modes, using single-molecule FRET. We discovered that RNase H acts as a processive exoribonuclease on the 3′ DNA overhang side but as a distributive non-sequence-specific endonuclease on the 5′ DNA overhang side of RNA:DNA hybrids or on blunt-ended hybrids. The high affinity of previously unidentified double-stranded (ds) and single-stranded (ss) DNA junctions flanking RNA:DNA hybrids may help RNase H find the hybrid substrates in long genomic DNA. Our study provides new insights into the multifunctionality of RNase H, elucidating unprecedented roles of junctions and ssDNA overhang on RNA:DNA hybrids.
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