Document Actions
Human POT1 disrupts telomeric G-quadrupl ... g telomerase extension in vitro
Human POT1 disrupts telomeric G-quadruplexes allowing telomerase extension in vitro.
68
The POT1 (protection of telomeres 1) protein binds the ssDNA overhangs at the ends of chromosomes in diverse eukaryotes. POT1 is essential for chromosome end-protection, as best demonstrated in fission yeast. In human cells, hPOT1 is also involved in telomere-length regulation. We now show that telomeric oligonucleotides, such as d[GGG(TTAGGG)(3)], which form intramolecular G-quadruplexes through Hoogsteen base-pairing, serve as only marginal primers for extension by recombinant human telomerase; telomerase stalls after every nucleotide addition. Addition of hPOT1 to the reaction restores the normal processive elongation pattern seen with primers that cannot form G-quadruplexes. hPOT1 does not act catalytically but, instead, forms a stoichiometric complex with the DNA, freeing its 3' tail. An antisense oligonucleotide, which base-pairs near the 5' end of the telomeric sequence, leaving a telomerase-extendable 3' tail, duplicates the effect of hPOT1 on activation of G-quadruplex primers. Thus, hPOT1 may function simply by trapping the unfolded forms of these telomeric primers in an equilibrium population. We propose an additional role for hPOT1 in telomere maintenance: disrupting G-quadruplex structures in telomeric DNA, thereby allowing proper elongation by telomerase.
Zaug AJ, Podell ER, Cech TR
Proceedings of the National Academy of Sciences of the United States of America
2005-08-02 00:00
102
31
10864-9
Base Sequence,DNA,DNA Primers,DNA-Binding Proteins,Humans,Macromolecular Substances,Models, Biological,Nucleic Acid Conformation,Recombinant Proteins,Telomerase,Telomere,Telomere-Binding Proteins,DNA Primers,DNA-Binding Proteins,Macromolecular Substances,POT1 protein, human,Recombinant Proteins,Telomere-Binding Proteins,DNA,Telomerase
Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA
Proc. Natl. Acad. Sci. U.S.A.
0027-8424
10.1073/pnas.0504744102
0504744102
193
True
16043710
