Replication termination

S. Codlin, and J. Z. Dalgaard, Complex mechanism of site-specific DNA replication termination in hssion yeast. EMBO J. 22, 3431-3440 (2003). 

Ter (Replication termination) xthA AP endonuclease holE DNA polymerase III subunit... 

Kainada, K., Iloriiiclii, T., Olisiimi, K., Shimamoto, N., Morikawa, K. (1996) Structure of a replication-terminator protein complexed with DNA. Nature 383, 598-603. 

Deuterolysin (1EB6) Replication Terminator Protein 1ECR)... 

Figure 11.6 Multiple origin of replication forks in eukaryotic DNA replication. Termination of replication occurs where two growth forks come together.

Why might it he advantageous to E. coli to have six replication terminators in its chromosome SOLUTION... 

Termination and telomere The binding of the replication termination protein (Tus protein) to the terminus region (x locus) in prokaryotic chromosome impedes the progression of the replication fork and terminates DNA replication. In eukaryotes, the linear chromosomes terminate with telomeres by the action of telomerase. 

DNA synthesis during S phase of the cell cycle resulting in a doubling of the genomic DNA. Replication can be subdivided into three distinct phases initiation, elongation, and termination. 

The nonstructural region of the precursor, harboring the viral replication machinery, is cut into its mature components in a maturation reaction in which two viral proteases (NS2-pro and NS3/4A-pro) cooperate. Site-directed mutagenesis of an other wise infectious cDNA has shown that both HCV-encoded proteases are necessary for viral infectivity, but most of the attention has so far been focused on one of them a member of the serine protease family (EC 3.4.21) located in the N-terminal region of the viral NS3 protein. 

DJ, Flores OA (2003) Characterization of resistance to non-obligate chain-terminating ribonu-cleoside analogs that inhibit hepatitis C virus replication in vitro. J Biol Chem 278 49164-49170... 

Performing crossover and mutation. In addition to replication, crossover and mutation are also two effective ways to form a new population. Crossover manipulation is the combination of two ABS codes to form two new ABS codes. Mutation changes one or two elements, saying 0 to 1, or 1 to 0, of a selected ABS code. The crossover and mutation are performed probabilistically. The replication, crossover, and mutation processes are repeated until the termination criterion is reached. 

Some nucleases are capable of hydrolyzing a nucleotide only when it is present at a terminal of a molecule these ate tefetted to as exonucleases. Exonucleases act in one direction (3 —> 5 ot 5 —> 30 only. In bacteria, a 3 —> 5 exonuclease is an integral part of the DNA replication machinery and there serves to edit— or proofread—the most recently added deoxynucleo-tide for base-pairing errors. 

Human immunodeficiency virus (HIV) is a retrovirus, i.e. its RNA is converted in human cells by the en me reverse transcriptase to DNA which is incorporated into the human genome and is responsible for producing new HIV particles. Zidovudine (azidothymidine, AZT Fig. 5.22F) is a stmctural analogue of thymidine (Fig. 5.22A) and is used to treat AIDS patients. Zidovudine is converted in both infected and uninfected cells to the mono-, di- and eventually triphosphate derivatives. Zidovudine triphosphate, the aetive form, is a potent inhibitor of HIV replication, being mistaken for thymidine by reverse transeriptase. Premature ehain termination of viral DNA ensues. However, AZT is relatively toxic because, as pointed out above, it is converted to the triphosphate by eellular enzymes and is thus also aetivated in uninfected cells. 

---