Abstract
Telomerase-negative immortalized human cells maintain telomeres by alternative lengthening of telomeres (ALT) pathway(s), which may involve homologous recombination. We find that endogenous BLM protein co-localizes with telomeric foci in ALT human cells but not telomerase positive immortal cell lines or primary cells. BLM interacts in vivo with the telomeric protein TRF2 in ALT cells, as detected by FRET and co-immunoprecipitation. Transient over-expression of green fluorescent protein (GFP)-BLM results in marked, ALT cell-specific increases in telomeric DNA. The association of BLM with telomeres and its effect on telomere DNA synthesis require a functional helicase domain. Our results identify BLM as the first protein found to affect telomeric DNA synthesis exclusively in human ALT cells and suggest that BLM facilitates recombination-driven amplification of telomeres in ALT cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphatases / biosynthesis
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Adenosine Triphosphatases / immunology
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Adenosine Triphosphatases / metabolism*
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Bloom Syndrome / enzymology*
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Bloom Syndrome / genetics*
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Cell Line
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Cell Line, Transformed
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Cell Nucleus
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DNA / biosynthesis*
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DNA Helicases / biosynthesis
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DNA Helicases / immunology
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DNA Helicases / metabolism*
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Fibroblasts / chemistry
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Fibroblasts / enzymology
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Fibroblasts / virology
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Green Fluorescent Proteins
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Humans
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Luminescent Proteins / biosynthesis
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Luminescent Proteins / genetics
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RecQ Helicases
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Recombinant Proteins / biosynthesis
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Recombinant Proteins / genetics
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Telomere / enzymology
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Telomere / genetics
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Telomere / metabolism*
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Telomeric Repeat Binding Protein 2 / immunology
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Telomeric Repeat Binding Protein 2 / metabolism*
Substances
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Luminescent Proteins
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Recombinant Proteins
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Telomeric Repeat Binding Protein 2
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Green Fluorescent Proteins
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DNA
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Adenosine Triphosphatases
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Bloom syndrome protein
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DNA Helicases
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RecQ Helicases