Human FEN-1 can process the 5'-flap DNA of CTG/CAG triplet repeat derived from human genetic diseases by length and sequence dependent manner

Lee, Suman; Park, Min S

doi:10.1038/emm.2002.44

Cited by 28 publications

(12 citation statements)

References 15 publications

(18 reference statements)

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“…1A). Others have reported previously that hFEN1 is somewhat less active on flaps containing longer CTG repeats (11 or more repeats), consistent with the possibility that activity depends upon repeat length (27). Its flap endonuclease activity predominated on the unstructured flap substrate, whereas 5Ј-excision predominated on the substrate containing a (CTG) 8 repeat within the flap (Fig.…”

Section: Hfen1 5ј-flap Cleavage Is Impaired By Ctg or Cgg Repeats-supporting

confidence: 77%

Complementary Roles for Exonuclease 1 and Flap Endonuclease 1 in Maintenance of Triplet Repeats

Vallur

Maizels

2010

Journal of Biological Chemistry

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Trinucleotide repeats can form stable secondary structures that promote genomic instability. To determine how such structures are resolved, we have defined biochemical activities of the related RAD2 family nucleases, FEN1 (Flap endonuclease 1) and EXO1 (exonuclease 1), on substrates that recapitulate intermediates in DNA replication. Here, we show that, consistent with its function in lagging strand replication, human (h) FEN1 could cleave 5-flaps bearing structures formed by CTG or CGG repeats, although less efficiently than unstructured flaps. hEXO1 did not exhibit endonuclease activity on 5-flaps bearing structures formed by CTG or CGG repeats, although it could excise these substrates. Neither hFEN1 nor hEXO1 was affected by the stem-loops formed by CTG repeats interrupting duplex regions adjacent to 5-flaps, but both enzymes were inhibited by G4 structures formed by CGG repeats in analogous positions. Hydroxyl radical footprinting showed that hFEN1 binding caused hypersensitivity near the flap/duplex junction, whereas hEXO1 binding caused hypersensitivity very close to the 5-end, correlating with the predominance of hFEN1 endonucleolytic activity versus hEXO1 exonucleolytic activity on 5-flap substrates. These results show that FEN1 and EXO1 can eliminate structures formed by trinucleotide repeats in the course of replication, relying on endonucleolytic and exonucleolytic activities, respectively. These results also suggest that unresolved G4 DNA may prevent key steps in normal post-replicative DNA processing.Short tandem nucleotide repeats are widespread in mammalian genomes (1) and prone to instability because of their potential to form alternative structures during replication, transcription, or recombination. Trinucleotide repeats are of particular interest because they are associated with at least 20 human neurodegenerative disorders (2). Fragile X syndrome, the second most common cause of mental retardation, is caused by CGG repeat expansion; myotonic dystrophy by CTG repeat expansion; and Huntington chorea by CAG repeat expansions (3). All three repeats can form stable secondary structures containing stem-loops or, in the case of the CGG repeat, G4 DNA (4 -6). Formation of secondary structures can affect DNA replication, and factors that promote Okazaki fragment maturation and lagging strand synthesis have been identified as critical to maintenance of repeat stability (7-9). Secondary structure formation can also impair transcription or lead to transcription-associated instability (10 -13).FEN1 (Flap endonuclease 1) is a highly conserved RAD2 family nuclease active in DNA repair and a component of the replisome in eukaryotic cells (14). The canonical activity of FEN1 is endonucleolytic excision of a 5Ј-flap from a duplex substrate, which represents the intermediate in processing Okazaki fragments during lagging strand replication (15). FEN1 can also function as an exonuclease and gap endonuclease. FEN1 is essential in mammalian cells (16). Yeast deficient in Rad27, the FEN1 homolog, exhibits growth d...

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Section: Hfen1 5ј-flap Cleavage Is Impaired By Ctg or Cgg Repeats-supporting

confidence: 77%

Complementary Roles for Exonuclease 1 and Flap Endonuclease 1 in Maintenance of Triplet Repeats

Vallur

Maizels

2010

Journal of Biological Chemistry

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“…Subsequently, further studies suggested that Okazaki fragment initiation and processing at sequences consisting of expanded triplet repeats might account for their instability (Cleary et al, 2002;Mirkin and Smirnova, 2002). In support of this model, the flap endonuclease (FEN-1) has been shown to cause CAG repeat instability when hemizygous in mice and when absent in yeast (Lee and Park, 2002;Spiro and McMurray, 2003). As mutations in mismatch repair genes cause expansions and contractions of normal length dinucleotide and trinucleotide repeats in yeast, mice, and humans (Aaltonen et al, 1993;Peltomaki et al, 1993;Strand et al, 1993;de Wind et al, 1998), a role for mismatch repair enzymes in expanded triplet repeat instability has also been examined.…”

Section: Introductionmentioning

confidence: 94%

A SCA7 CAG/CTG repeat expansion is stable in Drosophila melanogaster despite modulation of genomic context and gene dosage

Jackson

Whitworth

Greene

et al. 2005

Gene

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“…However, because of the singlestranded nature of the Okazaki fragments on the lagging strand, both expansions and deletions can occur depending on the stability of the hairpin structures formed by these repeats. The aberrant processing of the Okazaki fragments involving FEN-1 and DNA ligase has also been hypothesized to play an important role in generating genetic instabilities (21,(113)(114)(115)(116)(117)(118).…”

Section: Chemical Probe Determinations-d(cagg)mentioning

confidence: 99%

Hairpin Structure-forming Propensity of the (CCTG·CAGG) Tetranucleotide Repeats Contributes to the Genetic Instability Associated with Myotonic Dystrophy Type 2

Dere

Напиерала

Ranum

et al. 2004

Journal of Biological Chemistry

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The genetic instabilities of (CCTG⅐CAGG) n tetranucleotide repeats were investigated to evaluate the molecular mechanisms responsible for the massive expansions found in myotonic dystrophy type 2 (DM2) patients. DM2 is caused by an expansion of the repeat from the normal allele of 26 to as many as 11,000 repeats. Genetic expansions and deletions were monitored in an African green monkey kidney cell culture system (COS-7 cells) as a function of the length (30, 114, or 200 repeats), orientation, or proximity of the repeat tracts to the origin (SV40) of replication. As found for CTG⅐CAG repeats related to DM1, the instabilities were greater for the longer tetranucleotide repeat tracts. Also, the expansions and deletions predominated when cloned in orientation II (CAGG on the leading strand template) rather than I and when cloned proximal rather than distal to the replication origin. Biochemical studies on synthetic d(CAGG) 26 and d(CCTG) 26 as models of unpaired regions of the replication fork revealed that d(CAGG) 26 has a marked propensity to adopt a defined base paired hairpin structure, whereas the complementary d(CCTG) 26 lacks this capacity. The effect of orientation described above differs from all previous results with three triplet repeat sequences (including CTG⅐CAG), which are also involved in the etiologies of other hereditary neurological diseases. However, similar to the triplet repeat sequences, the ability of one of the two strands to form a more stable folded structure, in our case the CAGG strand, explains this unorthodox "reversed" behavior.

show abstract

Human FEN-1 can process the 5'-flap DNA of CTG/CAG triplet repeat derived from human genetic diseases by length and sequence dependent manner

Cited by 28 publications

References 15 publications

Complementary Roles for Exonuclease 1 and Flap Endonuclease 1 in Maintenance of Triplet Repeats

Complementary Roles for Exonuclease 1 and Flap Endonuclease 1 in Maintenance of Triplet Repeats

A SCA7 CAG/CTG repeat expansion is stable in Drosophila melanogaster despite modulation of genomic context and gene dosage

Hairpin Structure-forming Propensity of the (CCTG·CAGG) Tetranucleotide Repeats Contributes to the Genetic Instability Associated with Myotonic Dystrophy Type 2

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