Abstract
Mismatch repair contributes to genetic stability, and inactivation of the mammalian pathway leads to tumor development. Mismatch correction occurs by an excision-repair mechanism and has been shown to depend on the 5′ to 3′ hydrolytic activity exonuclease 1 (Exo1) in eukaryotic cells. However, genetic and biochemical studies have indicated that one or more Exo1-independent modes of mismatch repair also exist. We have analyzed repair of nicked circular heteroduplex DNA in extracts of Exo1-deficient mouse embryo fibroblast cells. Exo1-independent repair under these conditions is MutLα-dependent and requires functional integrity of the MutLα endonuclease metal-binding motif. In contrast to the Exo1-dependent reaction, we have been unable to detect a gapped excision intermediate in Exo1-deficient extracts when repair DNA synthesis is blocked. A possible explanation for this finding has been provided by analysis of a purified system comprised of MutSα, MutLα, replication factor C, proliferating cell nuclear antigen, replication protein A, and DNA polymerase δ that supports Exo1-independent repair in vitro. Repair in this system depends on MutLα incision of the nicked heteroduplex strand and dNTP-dependent synthesis-driven displacement of a DNA segment spanning the mismatch. Such a mechanism may account, at least in part, for the Exo1-independent repair that occurs in eukaryotic cells, and hence the modest cancer predisposition of Exo1-deficient mammalian cells.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 8495-8500 |
| Number of pages | 6 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 106 |
| Issue number | 21 |
| DOIs | |
| State | Published - May 26 2009 |
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Keywords
- Cancer
- DNA polymerase
- DNA repair
- Strand displacment
ASJC Scopus subject areas
- General
Cite this
A possible mechanism for exonuclease 1-independent eukaryotic mismatch repair. / Kadyrov, Farid A.; Genschel, Jochen; Fang, Yanan; Penland, Elisabeth; Edelmann, Winfried; Modrich, Paul.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 106, No. 21, 26.05.2009, p. 8495-8500.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - A possible mechanism for exonuclease 1-independent eukaryotic mismatch repair
AU - Kadyrov, Farid A.
AU - Genschel, Jochen
AU - Fang, Yanan
AU - Penland, Elisabeth
AU - Edelmann, Winfried
AU - Modrich, Paul
PY - 2009/5/26
Y1 - 2009/5/26
N2 - Mismatch repair contributes to genetic stability, and inactivation of the mammalian pathway leads to tumor development. Mismatch correction occurs by an excision-repair mechanism and has been shown to depend on the 5′ to 3′ hydrolytic activity exonuclease 1 (Exo1) in eukaryotic cells. However, genetic and biochemical studies have indicated that one or more Exo1-independent modes of mismatch repair also exist. We have analyzed repair of nicked circular heteroduplex DNA in extracts of Exo1-deficient mouse embryo fibroblast cells. Exo1-independent repair under these conditions is MutLα-dependent and requires functional integrity of the MutLα endonuclease metal-binding motif. In contrast to the Exo1-dependent reaction, we have been unable to detect a gapped excision intermediate in Exo1-deficient extracts when repair DNA synthesis is blocked. A possible explanation for this finding has been provided by analysis of a purified system comprised of MutSα, MutLα, replication factor C, proliferating cell nuclear antigen, replication protein A, and DNA polymerase δ that supports Exo1-independent repair in vitro. Repair in this system depends on MutLα incision of the nicked heteroduplex strand and dNTP-dependent synthesis-driven displacement of a DNA segment spanning the mismatch. Such a mechanism may account, at least in part, for the Exo1-independent repair that occurs in eukaryotic cells, and hence the modest cancer predisposition of Exo1-deficient mammalian cells.
AB - Mismatch repair contributes to genetic stability, and inactivation of the mammalian pathway leads to tumor development. Mismatch correction occurs by an excision-repair mechanism and has been shown to depend on the 5′ to 3′ hydrolytic activity exonuclease 1 (Exo1) in eukaryotic cells. However, genetic and biochemical studies have indicated that one or more Exo1-independent modes of mismatch repair also exist. We have analyzed repair of nicked circular heteroduplex DNA in extracts of Exo1-deficient mouse embryo fibroblast cells. Exo1-independent repair under these conditions is MutLα-dependent and requires functional integrity of the MutLα endonuclease metal-binding motif. In contrast to the Exo1-dependent reaction, we have been unable to detect a gapped excision intermediate in Exo1-deficient extracts when repair DNA synthesis is blocked. A possible explanation for this finding has been provided by analysis of a purified system comprised of MutSα, MutLα, replication factor C, proliferating cell nuclear antigen, replication protein A, and DNA polymerase δ that supports Exo1-independent repair in vitro. Repair in this system depends on MutLα incision of the nicked heteroduplex strand and dNTP-dependent synthesis-driven displacement of a DNA segment spanning the mismatch. Such a mechanism may account, at least in part, for the Exo1-independent repair that occurs in eukaryotic cells, and hence the modest cancer predisposition of Exo1-deficient mammalian cells.
KW - Cancer
KW - DNA polymerase
KW - DNA repair
KW - Strand displacment
UR - http://www.scopus.com/inward/record.url?scp=66649124883&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=66649124883&partnerID=8YFLogxK
U2 - 10.1073/pnas.0903654106
DO - 10.1073/pnas.0903654106
M3 - Article
C2 - 19420220
AN - SCOPUS:66649124883
VL - 106
SP - 8495
EP - 8500
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 21
ER -