TY - JOUR
T1 - POT1-TPP1 regulates telomeric overhang structural dynamics
AU - Hwang, Helen
AU - Buncher, Noah
AU - Opresko, Patricia L.
AU - Myong, Sua
N1 - Funding Information:
The authors thank Brian Freeman and Ruobo Zhou for careful review of the manuscript, members of the Myong and Opresko laboratory for helpful discussions, and M. Lei for the TPP1N plasmid construct. Support for this work was provided by the American Cancer Society (Research Scholar Grant; RSG-12-066-01-DMC), the Human Frontier Science Program (RGP0007/2012), and the U.S. National Science Foundation Physics Frontiers Center Program (0822613) through Center for the Physics of Living Cells for S.M.; the Linda Su-Nan Chang Sah Doctoral Fellowship for H.H.; and NIH Grant ES0515052 and the David Scaife Foundation grant to the Center for Nucleic Acid Science and Technology for P.O. H.H. labeled the TPP1N protein, conducted all of the experiments, and analyzed all of the data. N.B. purified all of the proteins. S.M. performed experiment design, analyses, and interpretation of the data. S.M. wrote the manuscript, and P.O. contributed to writing the manuscript.
PY - 2012/11/7
Y1 - 2012/11/7
N2 - Human telomeres possess a single-stranded DNA (ssDNA) overhang of TTAGGG repeats, which can self-fold into a G-quadruplex structure. POT1 binds specifically to the telomeric overhang and partners with TPP1 to regulate telomere lengthening and capping, although the mechanism remains elusive. Here, we show that POT1 binds stably to folded telomeric G-quadruplex DNA in a sequential manner, one oligonucleotide/oligosaccharide binding fold at a time. POT1 binds from 3′ to 5′, thereby unfolding the G-quadruplex in a stepwise manner. In contrast, the POT1-TPP1 complex induces a continuous folding and unfolding of the G-quadruplex. We demonstrate that POT1-TPP1 slides back and forth on telomeric DNA and also on a mutant telomeric DNA to which POT1 cannot bind alone. The sliding motion is specific to POT1-TPP1, as POT1 and ssDNA binding protein gp32 cannot recapitulate this activity. Our results reveal fundamental molecular steps and dynamics involved in telomere structure regulation.
AB - Human telomeres possess a single-stranded DNA (ssDNA) overhang of TTAGGG repeats, which can self-fold into a G-quadruplex structure. POT1 binds specifically to the telomeric overhang and partners with TPP1 to regulate telomere lengthening and capping, although the mechanism remains elusive. Here, we show that POT1 binds stably to folded telomeric G-quadruplex DNA in a sequential manner, one oligonucleotide/oligosaccharide binding fold at a time. POT1 binds from 3′ to 5′, thereby unfolding the G-quadruplex in a stepwise manner. In contrast, the POT1-TPP1 complex induces a continuous folding and unfolding of the G-quadruplex. We demonstrate that POT1-TPP1 slides back and forth on telomeric DNA and also on a mutant telomeric DNA to which POT1 cannot bind alone. The sliding motion is specific to POT1-TPP1, as POT1 and ssDNA binding protein gp32 cannot recapitulate this activity. Our results reveal fundamental molecular steps and dynamics involved in telomere structure regulation.
UR - http://www.scopus.com/inward/record.url?scp=84868552929&partnerID=8YFLogxK
U2 - 10.1016/j.str.2012.08.018
DO - 10.1016/j.str.2012.08.018
M3 - Article
C2 - 22981946
AN - SCOPUS:84868552929
SN - 0969-2126
VL - 20
SP - 1872
EP - 1880
JO - Structure
JF - Structure
IS - 11
ER -