Molecular mechanism of resolving trinucleotide repeat hairpin by helicases

Yupeng Qiu; Hengyao Niu; Lela Vukovic; Patrick Sung; Sua Myong

doi:10.1016/j.str.2015.04.006

Molecular mechanism of resolving trinucleotide repeat hairpin by helicases

Structure. 2015 Jun 2;23(6):1018-27. doi: 10.1016/j.str.2015.04.006. Epub 2015 May 21.

Authors

Yupeng Qiu¹, Hengyao Niu², Lela Vukovic³, Patrick Sung², Sua Myong⁴

Affiliations

¹ Bioengineering Department, University of Illinois, 1304 West Springfield Avenue, Urbana, IL 61801, USA.
² Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, PO Box 208024, New Haven, CT 06520, USA.
³ Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Physics Frontier Center (Center of Physics for Living Cells), University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA.
⁴ Bioengineering Department, University of Illinois, 1304 West Springfield Avenue, Urbana, IL 61801, USA; Institute for Genomic Biology, University of Illinois, 1206 West Gregory Street, Urbana, IL 61801, USA; Physics Frontier Center (Center of Physics for Living Cells), University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA; Biophysics and Computational Biology, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA. Electronic address: smyong@illinois.edu.

Abstract

Trinucleotide repeat (TNR) expansion is the root cause for many known congenital neurological and muscular disorders in human including Huntington's disease, fragile X syndrome, and Friedreich's ataxia. The stable secondary hairpin structures formed by TNR may trigger fork stalling during replication, causing DNA polymerase slippage and TNR expansion. Srs2 and Sgs1 are two helicases in yeast that resolve TNR hairpins during DNA replication and prevent genome expansion. Using single-molecule fluorescence, we investigated the unwinding mechanism by which Srs2 and Sgs1 resolves TNR hairpin and compared it with unwinding of duplex DNA. While Sgs1 unwinds both structures indiscriminately, Srs2 displays repetitive unfolding of TNR hairpin without fully unwinding it. Such activity of Srs2 shows dependence on the folding strength and the total length of TNR hairpin. Our results reveal a disparate molecular mechanism of Srs2 and Sgs1 that may contribute differently to efficient resolving of the TNR hairpin.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

DNA Helicases / metabolism*
Fluorescence
Fluorescence Resonance Energy Transfer
Inverted Repeat Sequences / genetics*
Models, Molecular*
Protein Conformation
Protein Unfolding*
RecQ Helicases / metabolism*
Saccharomyces cerevisiae Proteins / metabolism*
Trinucleotide Repeats / genetics*

Substances

Saccharomyces cerevisiae Proteins
SRS2 protein, S cerevisiae
SGS1 protein, S cerevisiae
DNA Helicases
RecQ Helicases

Abstract

Publication types

MeSH terms

Substances

Grants and funding