Regulatory Roles of p21 and Apurinic/Apyrimidinic Endonuclease 1 in Base Excision Repair

• Published in: The Journal of biological chemistry 2001-12, Vol.276 (52), p.48781-48789
• Main Authors: Tom, Samson, Ranalli, Tamara A., Podust, Vladimir N., Bambara, Robert A.
• Format: Article
• Language: English
• Subjects: Animals; APE1 protein; apurinic/apyrimidinic endonuclease 1; base excision repair; Carbon-Oxygen Lyases - metabolism; Cell Cycle - physiology; Cyclin-Dependent Kinase Inhibitor p21; Cyclins - metabolism; Deoxyribonuclease IV (Phage T4-Induced); DNA Damage; DNA Ligase ATP; DNA ligase I; DNA Ligases - metabolism; DNA Polymerase beta - metabolism; DNA Polymerase III - metabolism; DNA Repair - physiology; DNA-(Apurinic or Apyrimidinic Site) Lyase; Endodeoxyribonucleases - metabolism; Enzyme Activation; Enzyme Inhibitors - metabolism; FEN1 protein; Flap Endonucleases; Humans; p21 protein; Proliferating Cell Nuclear Antigen - chemistry; Proliferating Cell Nuclear Antigen - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109626200

Many types of DNA damage induce a cellular response that inhibits replication but allows repair by up-regulating the p53 pathway and inducing p21Cip1, Waf1, Sdi1. The p21 regulatory protein can bind proliferating cell nuclear antigen (PCNA) and prohibit DNA replication. We show here that p21 also inhibits PCNA stimulation of long patch base excision repair (BER) in vitro. p21 disrupts PCNA-directed stimulation of flap endonuclease 1 (FEN1), DNA ligase I, and DNA polymerase δ. The dilemma is to understand how p21 prevents DNA replication but allows BER in vivo. Differential regulation by p21 is likely to relate to the utilization of DNA polymerase β, which is not sensitive to p21, in the repair pathway. We have also found that apurinic/apyrimidinic endonuclease 1 (APE1) stimulates long patch BER. Furthermore, neither APE1 activity nor its ability to stimulate long patch BER is significantly affected by p21 in vitro. We propose that APE1 serves as an assembly and coordination factor for long patch BER proteins. APE1 initially cleaves the DNA and then facilitates the sequential binding and catalysis by DNA polymerase β, DNA polymerase δ, FEN1, and DNA ligase I. This model implies that BER can be regulated differentially, based upon the assembly of relevant proteins around APE1 in the presence or absence of PCNA.