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EUKARYOTIC DNA POLYMERASES<br />Course teacher :-<br />             Dr. P.NagraJan<br />  Dr . R.Renuka                   ...
Eukaryotic Replication<br />Cell growth and division divided into phases: M, G1, S, and G2<br />
Flow of Genetic Information in the Cell<br />Mechanisms by which information is transferred in the cell is based on “Centr...
INTRODUCTION<br />What is DNA polymerase ?<br />What is DNA replication ?<br />What is DNA proofreading ?<br />DNA polymer...
<ul><li>Family D
Family X</li></ul>e.g – pol β,pol µ,TdT<br /><ul><li>Family Y</li></ul>e.g – translesion synthesis polymerase<br /><ul><li...
Eukaryotic DNA Polymerase<br />At least 15 different polymerases are present in eukaryotes (5 have been studied more exten...
The Eukaryotic Replication Fork<br />The general features of DNA replication in eukaryotes are similar to those in prokary...
DNA polymerase function has the following requirements:<br />all four deoxyribonucleoside triphosphates: dTTP, dATP, dGTP,...
DNA Polymerase Reaction<br />The 3’-OH group at the end of the growing DNA chain acts as a nucleophile.<br />The phosphoru...
 EUKARYOTIC DNA POLYMERASE<br />Efficient machinery is required to maintain the genetic information.<br />DNA polymerases ...
No homologues for E. coli pol III exist in eukaryotes<br />Pol β is a major base excision repair pol , in animals pol λ ha...
3D structure of the DNA-binding helix-turn-helix motifs in human DNA polymerase beta<br />
DNA polymerase alpha-primase<br />DNA polymerase activity without exonuclease proofreading<br />consist of four subunits (...
DNA polymerase delta<br />The message level and enzyme activity of pol δ are up-regulated when quiescent cells are induced...
minor role in base excision repair in yeast <br />gap-filling function in mammalian, long-patch base excision repair<br />...
DNA polymerase epsilon<br />DNA polymerase epsilon (pol ε) was first purified as DNA polymerase II in 1970<br />PCNA indep...
Shows uniqecharcter in B class<br />catalytic properties and sensitivity to inhibitors<br />3’-5’ exonuclease activity<br ...
DNA polymerase switching and processing of an Okazaki fragment on the lagging strand<br />
Removal of dispalcedokazaki initiator RNA by FEN1/RTH1 nuclease<br />
Mismatch repair<br /><ul><li> Enzyme systems constantly moniter DNA looking for altered DNA</li></ul>Example – <br />     ...
Proofreading and Repair<br />DNA replication takes place only once each generation in each cell<br />Errors in replication...
DNA Polymerase Repair<br />
DNA polymerase with proofreading ability<br />
 DNA Double strand break repair pathway<br />
CONCLUSION<br />
DISSCUSSION<br />
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Molicular cell biology

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Molicular cell biology

  1. 1. EUKARYOTIC DNA POLYMERASES<br />Course teacher :-<br /> Dr. P.NagraJan<br /> Dr . R.Renuka Professor<br /> Presented by :-<br />Kale Ravindra Ramrao<br /> 09-607-05<br />
  2. 2. Eukaryotic Replication<br />Cell growth and division divided into phases: M, G1, S, and G2<br />
  3. 3. Flow of Genetic Information in the Cell<br />Mechanisms by which information is transferred in the cell is based on “Central Dogma”<br />
  4. 4. INTRODUCTION<br />What is DNA polymerase ?<br />What is DNA replication ?<br />What is DNA proofreading ?<br />DNA polymerase families ?<br /><ul><li>Family A</li></ul>e.g , mt DNA polymerase<br /><ul><li>Family B</li></ul>e.g – DNA polymerase a,d,e<br /><ul><li>Family C</li></ul>e.g – DNA pol III<br />
  5. 5. <ul><li>Family D
  6. 6. Family X</li></ul>e.g – pol β,pol µ,TdT<br /><ul><li>Family Y</li></ul>e.g – translesion synthesis polymerase<br /><ul><li>Family RT</li></ul>e.g - telomerase<br />
  7. 7. Eukaryotic DNA Polymerase<br />At least 15 different polymerases are present in eukaryotes (5 have been studied more extensively)<br />
  8. 8. The Eukaryotic Replication Fork<br />The general features of DNA replication in eukaryotes are similar to those in prokaryotes. Differences summarized in Table 10.5.<br />
  9. 9. DNA polymerase function has the following requirements:<br />all four deoxyribonucleoside triphosphates: dTTP, dATP, dGTP, and dCTP<br />Mg2+<br />an RNA primer <br />
  10. 10. DNA Polymerase Reaction<br />The 3’-OH group at the end of the growing DNA chain acts as a nucleophile.<br />The phosphorus adjacent to the sugar is attacked, and then added to the growing chain.<br />
  11. 11. EUKARYOTIC DNA POLYMERASE<br />Efficient machinery is required to maintain the genetic information.<br />DNA polymerases (pols) α, β, γ, δ, and ε are the key enzymes required to maintain the integrity of the genome. <br />DNA polymerases can be further subdivided into seven different families: A, B, C, D, X, Y, and RT.<br />The replicative pols α, δ and ε are related to pol II in E. coli and form the family B<br />
  12. 12. No homologues for E. coli pol III exist in eukaryotes<br />Pol β is a major base excision repair pol , in animals pol λ has an obvious role in meiosis-associated repair <br />pol µ is involved in somatic hyper mutation in lymph nodes <br />pol σ, that links DNA replication to the establishment of sister chromatid cohesion <br />
  13. 13.
  14. 14. 3D structure of the DNA-binding helix-turn-helix motifs in human DNA polymerase beta<br />
  15. 15. DNA polymerase alpha-primase<br />DNA polymerase activity without exonuclease proofreading<br />consist of four subunits (A, B, C, D)<br />expression of pol α (A subunit) takes place when inactive cell mitogenically activated to re-enter the cell cycle<br />pol α with strongly phosphorylated A and B subunits interacts with cyclin A and co-localizes in sites of ongoing DNA replication<br />
  16. 16. DNA polymerase delta<br />The message level and enzyme activity of pol δ are up-regulated when quiescent cells are induced to proliferate <br />transcription factors Sp1 and Sp3<br />The characteristic feature of pol δ is its tight coupling to the proliferating cell nuclear antigen (PCNA)<br />Pol δ is a major replicative polymerase <br />
  17. 17. minor role in base excision repair in yeast <br />gap-filling function in mammalian, long-patch base excision repair<br />a function for pol δ in recombination, double strand break repair, telomere maintenance and cell cycle checkpoint control<br />
  18. 18. DNA polymerase epsilon<br />DNA polymerase epsilon (pol ε) was first purified as DNA polymerase II in 1970<br />PCNA independent form of pol δ from calf thymus <br />Many of residues are important for nucleotide binding and/or template-primer stabilization<br />The mammalian pol ε has been purified as a dimeric enzyme<br />
  19. 19. Shows uniqecharcter in B class<br />catalytic properties and sensitivity to inhibitors<br />3’-5’ exonuclease activity<br />Pol ε does not need PCNA as an auxiliary factor for processive DNA synthesis <br />
  20. 20.
  21. 21. DNA polymerase switching and processing of an Okazaki fragment on the lagging strand<br />
  22. 22. Removal of dispalcedokazaki initiator RNA by FEN1/RTH1 nuclease<br />
  23. 23. Mismatch repair<br /><ul><li> Enzyme systems constantly moniter DNA looking for altered DNA</li></ul>Example – <br /> UV radiation causes two adjacent Thymines to form a Thymine dimer<br />When found, nuclase enzymes remove the TT dimer and a few surrounding nucleotides <br />DNA polymerase fills in the gap <br />
  24. 24. Proofreading and Repair<br />DNA replication takes place only once each generation in each cell<br />Errors in replication (mutations) occur spontaneously only once in every 109 to 1010 base pairs<br />Can be lethal to organisms<br />Errors in hydrogen bonding lead to errors in a growing DNA chain once in every 104 to 105 base pairs<br />
  25. 25. DNA Polymerase Repair<br />
  26. 26. DNA polymerase with proofreading ability<br />
  27. 27.
  28. 28. DNA Double strand break repair pathway<br />
  29. 29. CONCLUSION<br />
  30. 30. DISSCUSSION<br />
  31. 31. THANK YOU<br />

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