Eukaryotic DNA contains at least 15 different polymerases that are classified into 7 families and play various roles in DNA replication and repair. DNA polymerase alpha, delta, and epsilon are the major replicative polymerases and are involved in DNA replication and other processes like recombination and repair. Polymerases conduct DNA replication through synthesizing a new strand while using the existing DNA strand as a template. They add nucleotides through phosphodiester bond formation between the 3' hydroxyl group of the growing strand and 5' phosphate of the incoming nucleotide. Eukaryotic DNA replication involves multiple polymerases and accessory proteins working together in a coordinated manner.

1. EUKARYOTIC DNA POLYMERASES Course teacher :- Dr. P.NagraJan Dr . R.Renuka Professor Presented by :- Kale Ravindra Ramrao 09-607-05

2. Eukaryotic Replication Cell growth and division divided into phases: M, G1, S, and G2

3. Flow of Genetic Information in the Cell Mechanisms by which information is transferred in the cell is based on “Central Dogma”

7. Eukaryotic DNA Polymerase At least 15 different polymerases are present in eukaryotes (5 have been studied more extensively)

8. The Eukaryotic Replication Fork The general features of DNA replication in eukaryotes are similar to those in prokaryotes. Differences summarized in Table 10.5.

9. DNA polymerase function has the following requirements: all four deoxyribonucleoside triphosphates: dTTP, dATP, dGTP, and dCTP Mg2+ an RNA primer

10. DNA Polymerase Reaction The 3’-OH group at the end of the growing DNA chain acts as a nucleophile. The phosphorus adjacent to the sugar is attacked, and then added to the growing chain.

11. EUKARYOTIC DNA POLYMERASE Efficient machinery is required to maintain the genetic information. DNA polymerases (pols) α, β, γ, δ, and ε are the key enzymes required to maintain the integrity of the genome. DNA polymerases can be further subdivided into seven different families: A, B, C, D, X, Y, and RT. The replicative pols α, δ and ε are related to pol II in E. coli and form the family B

12. No homologues for E. coli pol III exist in eukaryotes Pol β is a major base excision repair pol , in animals pol λ has an obvious role in meiosis-associated repair pol µ is involved in somatic hyper mutation in lymph nodes pol σ, that links DNA replication to the establishment of sister chromatid cohesion

14. 3D structure of the DNA-binding helix-turn-helix motifs in human DNA polymerase beta

15. DNA polymerase alpha-primase DNA polymerase activity without exonuclease proofreading consist of four subunits (A, B, C, D) expression of pol α (A subunit) takes place when inactive cell mitogenically activated to re-enter the cell cycle pol α with strongly phosphorylated A and B subunits interacts with cyclin A and co-localizes in sites of ongoing DNA replication

16. DNA polymerase delta The message level and enzyme activity of pol δ are up-regulated when quiescent cells are induced to proliferate transcription factors Sp1 and Sp3 The characteristic feature of pol δ is its tight coupling to the proliferating cell nuclear antigen (PCNA) Pol δ is a major replicative polymerase

17. minor role in base excision repair in yeast gap-filling function in mammalian, long-patch base excision repair a function for pol δ in recombination, double strand break repair, telomere maintenance and cell cycle checkpoint control

18. DNA polymerase epsilon DNA polymerase epsilon (pol ε) was first purified as DNA polymerase II in 1970 PCNA independent form of pol δ from calf thymus Many of residues are important for nucleotide binding and/or template-primer stabilization The mammalian pol ε has been purified as a dimeric enzyme

19. Shows uniqecharcter in B class catalytic properties and sensitivity to inhibitors 3’-5’ exonuclease activity Pol ε does not need PCNA as an auxiliary factor for processive DNA synthesis

21. DNA polymerase switching and processing of an Okazaki fragment on the lagging strand

22. Removal of dispalcedokazaki initiator RNA by FEN1/RTH1 nuclease

24. Proofreading and Repair DNA replication takes place only once each generation in each cell Errors in replication (mutations) occur spontaneously only once in every 109 to 1010 base pairs Can be lethal to organisms Errors in hydrogen bonding lead to errors in a growing DNA chain once in every 104 to 105 base pairs

25. DNA Polymerase Repair

26. DNA polymerase with proofreading ability

28. DNA Double strand break repair pathway

29. CONCLUSION

30. DISSCUSSION

31. THANK YOU