FEN1 contributes to telomere stability in ALT-positive tumor cells

Saharia, Abhishek; Stewart, Sheila A.

doi:10.1038/onc.2008.458

Cited by 39 publications

(41 citation statements)

References 35 publications

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“…Cell Culture-All cells were grown as reported (25)(26)(27)(28). Briefly, cells were grown at 37°C in 5% CO 2 .…”

Section: Methodsmentioning

confidence: 99%

“…Virus Production and Infection-Lentiviral production and cell infections were carried out as described (25,26,29). Briefly, 293T cells were transfected with TransIT-LT1 (Mirius, Madison, WI).…”

Section: Methodsmentioning

confidence: 99%

“…Recently, we demonstrated that FEN1 is vital for telomere stability (25). Indeed, FEN1 depletion in telomerase-deficient cells leads to a DNA damage response at telomeres and telomere dysfunction characterized by loss of lagging strand-replicated sister telomeres (STLs) (25,26). Furthermore, genetic rescue experiments demonstrate that the nuclease activity and the C-terminal WRNinteracting domain of FEN1 are important for telomere stability (25).…”

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confidence: 99%

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FEN1 Ensures Telomere Stability by Facilitating Replication Fork Re-initiation

Saharia

Teasley

Duxin

et al. 2010

Journal of Biological Chemistry

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Telomeres are terminal repetitive DNA sequences whose stability requires the coordinated actions of telomere-binding proteins and the DNA replication and repair machinery. Recently, we demonstrated that the DNA replication and repair protein Flap endonuclease 1 (FEN1) is required for replication of lagging strand telomeres. Here, we demonstrate for the first time that FEN1 is required for efficient re-initiation of stalled replication forks. At the telomere, we find that FEN1 depletion results in replicative stress as evidenced by fragile telomere expression and sister telomere loss. We show that FEN1 participation in Okazaki fragment processing is not required for efficient telomere replication. Instead we find that FEN1 gap endonuclease activity, which processes DNA structures resembling stalled replication forks, and the FEN1 interaction with the RecQ helicases are vital for telomere stability. Finally, we find that FEN1 depletion neither impacts cell cycle progression nor in vitro DNA replication through non-telomeric sequences. Our finding that FEN1 is required for efficient replication fork re-initiation strongly suggests that the fragile telomere expression and sister telomere losses observed upon FEN1 depletion are the direct result of replication fork collapse. Together, these findings suggest that other nucleases compensate for FEN1 loss throughout the genome during DNA replication but fail to do so at the telomere. We propose that FEN1 maintains stable telomeres by facilitating replication through the G-rich lagging strand telomere, thereby ensuring high fidelity telomere replication.

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“…Cell Culture-All cells were grown as reported (25)(26)(27)(28). Briefly, cells were grown at 37°C in 5% CO 2 .…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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FEN1 Ensures Telomere Stability by Facilitating Replication Fork Re-initiation

Saharia

Teasley

Duxin

et al. 2010

Journal of Biological Chemistry

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“…Rad52, which interacts with Rad51, forms a heptameric ring that binds single-stranded DNA ends and catalyzes the DNA-DNA interaction necessary for the annealing of complementary strands (39,40). Recent studies have demonstrated that other proteins, including flap endonuclease 1 (FEN1), MUS81, the Fanconi anaemia group D2 (FANCD2) and Fanconi anaemia group A (FANCA) are also significant for ALT mechanisms (41)(42)(43). These proteins are significant in telomere maintenance, as shown by previous studies (44,45).…”

Section: A B C Dmentioning

confidence: 99%

Different expression of alternative lengthening of telomere (ALT)-associated proteins/mRNAs in osteosarcoma cell lines

et al. 2011

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Abstract. Tumors, including osteosarcoma (OS), are capable of evading senescence and cell death, which is caused by telomere loss with cell division. Alternative lengthening of telomeres (ALT) is considered as the main telomere maintenance mechanism in OS. In this study, we investigated the expression of ALT-associated proteins and mRNAs in human OS cell lines. Western blotting was used to detect the protein expression in OS cell lines, while the expression of mRNA was determined by reverse-transcriptase PCR and quantitative real-time PCR analysis. Whole-genome expression arrays were used to analyze the expression of all the mRNAs involved in telomere maintenance mechanisms (TMMs) including human telomerase reverse transcriptase, promyelocytic leukemia proteins and other related proteins. OS and normal cell lines do not express telomerase reverse transcriptase (hTERT) as a key subunit of telomerase, although they show varying levels of ALT-associated proteins and mRNAs such as PML, Rad52, MRE11 and FEN1 by Western blotting and quantitative real-time PCR analysis. A number of mRNAs that play essential roles in ALT are expressed more in OS cell lines than in the osteoblast cell line, as shown by whole-genome expression arrays. In conclusion, OS cell lines maintain their telomere length primarily through the ALT mechanism. There are numerous other proteins that regulate this process in OS; therefore, anti-ALT therapy may be a more effective method to treat OS than anti-telomerase therapy.

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“…1-3 Several factors either not directly involved in HR or having multiple functions are also essential for ALT telomere maintenance, for example the flap endonuclease FEN1 18 and the single ss DNA binding protein RPA. 19 The long noncoding RNA 'telomeric repeat-containing RNA' (TERRA), a DNA-dependent RNA polymerase II transcript produced from chromosome ends, 20,21 is emerging as a novel feature associated to ALT.…”

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confidence: 99%