Switching human telomerase on and off with hPOT1 protein in vitro.
POT1 (protection of telomeres 1) protein binds the G-rich single-stranded telomeric DNA at the ends of chromosomes. In human cells hPOT1 is involved in telomere length regulation, but the mechanism of this regulation remains unknown. Examination of the high-resolution crystal structure of the hPOT1-TTAGGGTTAG complex suggested that it would not be extended by telomerase, a hypothesis that we confirm by in vitro assays with recombinant telomerase. On the other hand, when hPOT1 is bound at a position one telomeric repeat before the 3'-end, leaving an 8-nucleotide 3'-tail, the complex is extended with improved activity and processivity. Thus, depending on its location relative to the DNA 3'-end, hPOT1 can either inhibit telomerase action or form a preferred substrate for telomerase. We propose that another factor catalyzes the interconversion of these states in vivo.
Lei
Ming
M
Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
Zaug
Arthur J
AJ
Podell
Elaine R
ER
Cech
Thomas R
TR
D017398:Alternative Splicing; D001665:Binding Sites; D003460:Crystallization; D004247:DNA / Q000378:metabolism; D017931:DNA Primers; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors; D006388:Hemagglutinins; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D000089804:Shelterin Complex; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016615:Telomere / Q000737:chemistry / Q000235:genetics; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; D004277:DNA, Single-Stranded; D004791:Enzyme Inhibitors; D006388:Hemagglutinins; D009841:Oligonucleotides; C440849:POT1 protein, human; D011994:Recombinant Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D004247:DNA; D019098:Telomerase