Association and regulation of the BLM helicase by the telomere proteins TRF1 and TRF2.
In addition to increased DNA-strand exchange, a cytogenetic feature of cells lacking the RecQ-like BLM helicase is a tendency for telomeres to associate. We also report additional cellular and biochemical evidence for the role of BLM in telomere maintenance. BLM co-localizes and complexes with the telomere repeat protein TRF2 in cells that employ the recombination-mediated mechanism of telomere lengthening known as ALT (alternative lengthening of telomeres). BLM co-localizes with TRF2 in foci actively synthesizing DNA during late S and G2/M; co-localization increases in late S and G2/M when ALT is thought to occur. Additionally, TRF1 and TRF2 interact directly with BLM and regulate BLM unwinding activity in vitro. Whereas TRF2 stimulates BLM unwinding of telomeric and non-telomeric substrates, TRF1 inhibits BLM unwinding of telomeric substrates only. Finally, TRF2 stimulates BLM unwinding with equimolar concentrations of TRF1, but not when TRF1 is added in molar excess. These data suggest a function for BLM in recombination-mediated telomere lengthening and support a model for the coordinated regulation of BLM activity at telomeres by TRF1 and TRF2.
Lillard-Wetherell
Kate
K
Department of Molecular Genetics, Biochemistry and Microbiology, Howard Hughes Medical Institute, University of Cincinnati College of Medicine, OH 45267, USA.
Machwe
Amrita
A
Langland
Gregory T
GT
Combs
Kelly A
KA
Behbehani
Gregory K
GK
Schonberg
Steven A
SA
German
James
J
Turchi
John J
JJ
Orren
David K
DK
Groden
Joanna
J
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001483:Base Sequence; D001973:Bromodeoxyuridine; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D020732:Cytogenetic Analysis; D004265:DNA Helicases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017404:In Situ Hybridization, Fluorescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D053484:RecQ Helicases; D016615:Telomere / Q000235:genetics* / Q000378:metabolism; D035321:Telomeric Repeat Binding Protein 1 / Q000378:metabolism*; D035341:Telomeric Repeat Binding Protein 2 / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D015003:Yeasts
D009841:Oligonucleotides; D035321:Telomeric Repeat Binding Protein 1; D035341:Telomeric Repeat Binding Protein 2; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; D004265:DNA Helicases; D053484:RecQ Helicases; D001973:Bromodeoxyuridine