DNA复制(DNA Replication)英文版

1、静思笃行 持中秉正 Wuhan University The College of Life Science*大学大学WWW.SOPPT.CNContents13Initiation of DNA Replication4Elongation of DNA Replication5Finishing of DNA Replication6The Concepts of DNA Replication Enzyme and Protein Involved in Replication 2Materials And Special Constructure of DNA*大学大学WWW.SOPP

2、T.CNThe Concepts of DNA Replication DNA replication is a process in which two same copies can be obtained.DNA replication is semi-conservative, one strand serves as the template for the second strand. Furthermore, DNA replication only occurs at a specific step in the cell cycle. *大学大学WWW.SOPPT.CNMat

3、erialsTemplate:One of the strand of dsDNA; dNTPs:4 kinbs of deoxynucleotide triphosphates, thats,ATP,GTP,CTP,TTP; Primer:usually RNA; Proteins and enzyme:such as DNA polymerase,DNA helicase,Singlestrand DNA binding protein （SSB）,DNA topoisomerase,DNA ligase,Telomerase (special in euka-ryotes);*大学大学W

4、WW.SOPPT.CNSpecial Constructure of DNA During ReplicationThe entire set of cis-acting DNA sequences that is sufficient to direct the initiation of DNA replicationDistinction between the replicator and origin of re-plication -Origin of replication is always a part of the replicator.ReplicatorThe spec

5、ific sites at which DNA unwinding and initiation of replication occur,are required for DNAreplication initiation.Its sequence are rich in AT , usually is a cross st-ructureorigin*大学大学WWW.SOPPT.CNSpecial Constructure of DNA During Replication Replicon As a unit for replication a DNA sequence.It cont-

6、ains a replicationorigin, some times it also contains a finishing sequence.Eukaryotic repliconProtokaryotic replicon*大学大学WWW.SOPPT.CNSpecial Constructure of DNA During Replication Replication Fork Its the Y shape area formed by dsDNA which is being replicated.Unwinded two single templateDNA and the

7、new chains which is being synthetized consist ofthe head of Y , and dsDNA template constitutes the tail of Y.*大学大学WWW.SOPPT.CNSpecial Constructure of DNA During Replication Okazaki fragmentIn DNA discontinuous reproduction, its the DNA fragments synth-etized using the lagging strand template.Then th

8、ey are covalent connected to a ssDNA. Its length is different in prokaryote andeukaryote.*大学大学WWW.SOPPT.CNEnzyme and Protein Involved in Replication DNA polymerase; DNA helicase; Singlestrand DNA binding protein （SSB）; DNA topoisomerase; DNA ligase; Initiator;*大学大学WWW.SOPPT.CNEnzyme and Protein Invo

9、lved in Replication DNA polymerase It is the enzyme using one of strand of dsDNA as a template to synthetize new DNA .It has two domains thats, palm domain, thumb domain and fingers domain.It has three activity,3-5 and 5-3 exonu-clease activity;DNA polymerase.DNA helicase In discontinuous re-product

10、ion of DNA, it integrats in front of replication fork, catal-yzing double chains of DNA to unlink. And it has the activity of ATPase, so two kinds of activivity coupling, by using the activity of ATPase as the en-ergy to unlink two chains. 3 SSB It Integrats with ssDNA unlinked by DNA helicase in re

11、p-lication fork,to prev-ent ssDNA rematch-ing and to protect it from degradating by protein or nucleic acid enzymes.12*大学大学WWW.SOPPT.CNEnzyme and Protein Involved in ReplicationDNA topoisomerase This enzyme cat-alyzes the formation of negative supercoi-ls that is thought to aid with the unwindi-ng p

12、rocess. DNA Ligase Nicks occur in the deve-loping molecule becau-se the RNA primer is removed and synthesis pro-ceeds in a disconti-nuous manner on the lagging strand. The final replicationpro-duct does not have any nicks bec-ause DNA ligase forms a covalent phosphodie-ster bond between 3-hydroxyl a

13、nd 5-phosphate groups. 6 Initiator A protein specifica-lly recognizes a DNA element in the rep-licator and activates the initiation of replic-ation.45*大学大学WWW.SOPPT.CNInitiation of DNA ReplicationIn E.coli，Dna A bonds 9bp reverse repeat sequences,and degenerates 13bpsequences.Then open initiation co

14、mplex is formed.In the condition that ATP offer energy,13bpare unlinked.At that time all ssDNAare covered by SSB.Dna B unlinks dsDNA template in replication fork.Primase catalysizes to synthetize primers.Core I adds dNTP to 3-OH on leading chain template and continues to synthetze leading chain*大学大学

15、WWW.SOPPT.CNInitiation of DNA Replication*大学大学WWW.SOPPT.CNElongation of DNA ReplicationThe Constructure of Elongation DNA Replication*大学大学WWW.SOPPT.CNElongation of DNA Replication After RNA primer is synthetized later, the elongation of DNAbegins. The leading chain is continuously synthetized, and t

16、he lagging chain is discontinuously synthetized.In the replication fork, DNA helicase moves from 5 to 3 on the DNA template .DNA primase periodically bonds with helicase, and synthetizes new primer in the lagging chain template . Afteran Okazaki fragment is completely synthetized,the core which is r

17、espon-sible for the Okazaki fragment, slides from the sliding clamp and DNA. *大学大学WWW.SOPPT.CNElongation of DNA Replication*大学大学WWW.SOPPT.CNElongation of DNA Replication*大学大学WWW.SOPPT.CNElongation of DNA Replication*大学大学WWW.SOPPT.CNElongation of DNA Replication Then,a new sliding clamp is formed to

18、synthetize new Okazaki fragment.The new Okazaki fragment and the former Okazaki fragment are separated by a incision. DNA polymerase I bonds with the incision, and uses its 5-3exonu-clease activity to cut down the RNA of Okazaki fragment.When the RNAprimer is re-moved, the DNA ligase catalyzes to sy

19、nthetize phosphodiester bond,thus Okazaki fragment being linked to form a continuousDNA lagging strand without RNA. During the DNA replication the DNA topoisomerase is involved.*大学大学WWW.SOPPT.CNElongation of DNA Replication*大学大学WWW.SOPPT.CNElongation of DNA Replication*大学大学WWW.SOPPT.CNFinishing of D

20、NA Replication（prokaryote） The replication of bacterial genome is from a single site of two-way and stop at the expectative replication terminat-ion area. There are serval termination sites (Ter). After the protein Tus ,which bonds with The Specific sequences, bonds with the termination sites,it onl

21、y blocks a replication fork, and doesnt work to the other,which ensures that two replication fork from the opposite direction can always meet, when one meets the other , DNAreplication is comple-ted.*大学大学WWW.SOPPT.CNFinishing of DNA Replication（Prokaryote）Finishing of DNA Replication of E.coli*大学大学W

22、WW.SOPPT.CNFinishing of DNA Replication（Eukaryote） Telomere Telomere is the specific DNA-protein complex structure at the end of eukaryotic chromosomes, which consists of the specific simple tandem repea-ting units, to offset the degradation of DNA caused by replication.*大学大学WWW.SOPPT.CNFinishing of DNA Replication（Eukaryote） Telomerase Telomerase is a kind reverse transcriptase carrying a templ-ate, which consists of RNA and protein complex. RNA component contains a short template