TY - JOUR
T1 - Telomeric overhang length determines structural dynamics and accessibility to telomerase and ALT-associated proteins
AU - Hwang, Helen
AU - Kreig, Alex
AU - Calvert, Jacob
AU - Lormand, Justin
AU - Kwon, Yongho
AU - Daley, James M.
AU - Sung, Patrick
AU - Opresko, Patricia L.
AU - Myong, Sua
PY - 2014/6/10
Y1 - 2014/6/10
N2 - Summary The G-rich single-stranded DNA at the 3′ end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single-molecule fluorescence spectroscopy, we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compared with four repeats, showed much greater dynamics and accessibility to telomerase binding and activity and loading of the ALT-associated proteins RAD51, WRN, and BLM. Although the eight repeats are highly dynamic, they can fold into two GQs, which limited protein accessibility. In contrast, the telomere-specific protein POT1 is unique in that it binds independently of repeat number. Our results suggest that the telomeric overhang length and dynamics may contribute to the regulation of telomere extension via telomerase action and the ALT mechanism.
AB - Summary The G-rich single-stranded DNA at the 3′ end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single-molecule fluorescence spectroscopy, we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compared with four repeats, showed much greater dynamics and accessibility to telomerase binding and activity and loading of the ALT-associated proteins RAD51, WRN, and BLM. Although the eight repeats are highly dynamic, they can fold into two GQs, which limited protein accessibility. In contrast, the telomere-specific protein POT1 is unique in that it binds independently of repeat number. Our results suggest that the telomeric overhang length and dynamics may contribute to the regulation of telomere extension via telomerase action and the ALT mechanism.
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U2 - 10.1016/j.str.2014.03.013
DO - 10.1016/j.str.2014.03.013
M3 - Article
C2 - 24836024
AN - SCOPUS:84902289206
VL - 22
SP - 842
EP - 853
JO - Structure with Folding & design
JF - Structure with Folding & design
SN - 0969-2126
IS - 6
ER -