Replication termination protein

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)... 

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. 

Many of the proteins and enzymes involved in initiation at replication origins and DNA chain growth at replication forks have the same biochemical activities as their counterparts in bacteria. However, the situation regarding terminators and terminator proteins is less clear. Whether they exist to delineate to any extent individual replicons or clusters of replicons is not known. In the case of eukaryotic chromosomes, however, there is a special mechanism to replicate their ends which are known as telomeres. 

Yet another solution to this problem is used by some viruses. Phage < )29 of Bacillus subtilis primes the replication of its 19,285 bp dsDNA at both ends by a terminal protein, which is linked covalently through its Ser 232 - OH group to dAMP. The 3 -OH of the deoxyadenosyl group primes the DNA replication. In a similar fashion replication of the eukaryotic adenoviruses, whose genome is a 35- to... 

The core of an adenoviral particle consists of the DNA genome complexed with four polypeptides (pV, pVII, mu, TP). Figure 10.1-4 schematically shows the structure of an adenovirus genome. The extremities contain inverted terminal repeat (ITR) sequences (100-140bp), covalently linked to terminal proteins (TPs), which function as replication origins [23]. The nearby / sequence at the left end of the... 

It seems quite clear that cellular factors participate in later steps in adenoviral DNA synthesis, for the in vitro systems that permit complete and faithful replication of a viral DNA-terminal protein template are dependent on them (Nagata et ai, 1983). Thus, competition for a cellular protein that functions beyond initiation also remains a real possibility. Unfortunately, the detailed examinations of the properties of cellular DNA made as the inhibitory effects of an adenovirus infection take hold, which are necessary to assess such an hypothesis, have not been performed. In the one study of this kind reported. Pater... 

Fig. 5. Schematic representation of adenovirus replication. The linear viral genome with the 5 -linked, terminal protein, , 55K is shown associated with the 87K precursor to the terminal protein, 0, to which CMP has become covalently linked in the first step of the initiation reaction, priming. A new DNA chain is then elongated from this primer, displacing its parental homologue (steps 1 and 2 in the figure). This displaced strand is believed to circularize by virtue of the inverted terminal repetition, represented as a-a, to form a double-stranded, terminal segment that is identical to that of the parental DNA. Such a scheme was originally proposed by Rekosh et ai (1977) and has been modified to include the priming role of the precursor to the terminal protein discussed in the text.

Challberg, M. D., Castrove, J. M., and Kelly, T. J., 1982, Initiation of adenovirus DNA replication Detection of covalent complexes between nucleotide and the 80 kilodalton terminal proteins, J. Virol. 41 265. 

Enomoto, T., Lichy, J. H., Ikeda, J. E., and Herwitz, J., 1981, Adenovirus DNA replication in vitro Purification of the terminal protein in a functional form, Proc. Natl. Acad. Sci. USA 78 6779. 

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. 

Whether the DNA replication checkpoint directly affects the Plxl activation pathway for Cdc25C has not yet been established. It is possible that the replication checkpoint arrests the cell cycle prior to initiation of the Plxl kinase cascade. Further characterization of upstream components of the cascade should reveal whether it is directly regulated by replication checkpoint activation. Such a characterization will also have importance for other M phase events, inasmuch as Plxl also regulates bipolar spindle formation, APC activation and cytokinesis (Qian et al 1998, 1999). These multiple functions of Plxl are associated with changes in localization of Plxl, and are most likely mediated by protein—protein interaction with the polo box motif in the non-catalytic C-terminal half of Plxl. 

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