DNA replication.txt

3’ to 5’ exonuclease activity of DNA polymerase responsible for removing an incorrectly incorporated nucleotide

a reverse transcriptase (synthesize DNA from an RNA template) responsible for replicating the tandem repeats of simple-sequence DNA at the telomeres

enzymes that catalyze the reversible breakage and rejoining of DNA strands to prevent the unchecked rotation of DNA that occurs ahead of the replication fork. The breaks serve as “swivels” that allow the two strands of template DNA to rotate freely around each other so that replication can proceed without twisting the DNA ahead of the fork.

stabilize the unwound template DNA, keeping it in an extended single-stranded state so that it can be copied by the polymerase

specifically recognize and bind DNA at the junction between the primer and template. After binding of the sliding-clamp protein, clamp proteins then load the DNA polymerase onto DNA at the primer-template junction.

multimeric protein complex responsible for recognizing the origin of replication; one member of this complex, the initiator protein, which unwinds the origin DNA and recruits the other proteins involved in synthesis

catalyzes the joining of deoxyribonucleotide 5’-triphosphates (dNTPs) to form the growing DNA chain; synthesizes DNA only in the 5’ to 3’ direction; can add a new dNTP only to a preformed primer strand that is hydrogen bonded to the template; dimerizes

begins to unwind the origin DNA and recruits the other proteins involved in synthesis. Helicase and SS DNA-binding proteins continue unwinding exposing the DNA template.

Region of active DNA synthesis

10⁴ However 1 bp per 10⁹ 10¹⁰ nucleotides

DNA polymerase. 5' to 3' and 3' to 5' exonuclease activity. 5' to 3' activity removes Okazaki fragments. 3' to 5' exonuclease participates in the proofreading of newly synthesized DNA.

telomerase, complementary to the telomere repeat sequences

5' to 3'

Exonuclease

Endonuclease

• 1.ReCognizion of Ori 2. binding of initiation site. ORI 3. unwinding of DNA by MCM helicase
• 4. Single stranded DNA binding protein (RPA) 5. Primase 6.Binding of RFC, PCNA, andrecruitment of DNA-Pol 7. Elongation (Replication) 8. Elimination of RNA primers 9. Ligation

Ribonuclease. Degrades RNA into smaller components.

catalyze the formation of a bond between two substrate molecules through hydrolysis

helps increase the processivity of leading strand synthesis during DNA replication

The sliding clamps of chromosomal replicases are acted upon by both the clamp loader and DNA polymerase.Several other proteins and polymerases also interact with the clamp. These proteins bind theclamp at the same spot and use it in sequential fashion. First the clamp loader must bind the clamp inorder to load it onto DNA, but directly thereafter the clamp loader must clear away from the clamp soit can be used by the replicative DNA polymerase. At the end of replication, the replicase is ejected fromthe clamp, which presumably allows the clamp to interact with yet other proteins after its use by thereplicase.