Proteins Involved in DNA Replication

The first method involves isolation of proteins with enzymatic activities that are logically related to the replication process, such as DNA polymerases and ligases. This is 

DnaA dnaA Initiator protein Binds oriC promotes double-helix opening DnaB loading 

DnaC dnaC Complexes with DnaB delivers DnaB to DNA 

Poll polA Prime removal and gap filling Initial leading strand synthesis on ColEl 

Gyrase gyrA Type II topoisomerase replication swivel, DNA 

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Since the uncontrolled proliferation is a peculiar characteristic of cancer cells, the proteins involved in DNA replication are attractive targets in modem chemotherapy. Several preclinical works showed in colorectal tumors, higher... 

The mechanism of replication in eukaryotes is believed to be very similar to this. However, the details have not yet been completely worked out. The steps and proteins involved in DNA replication in prokaryotes are compared with those used in eukaryotes in Table 1-2-2. 

Table 20.3 Some enzymes and binding proteins involved in DNA replication...

Growth during Replication Is Bidirectional Growth at the Replication Forks Is Discontinuous Proteins Involved in DNA Replication Characterization of DNA Polymerase I in Vitro Crystallography Combined with Genetics to Produce a Detailed Picture of DNA Poll Function... 

Table 26.1 contains a list of some proteins involved in DNA replication and their functions. How does one go about analyzing such a complex situation Historically, three general methods have been used for the identification and characterization of the proteins involved in DNA replication Purification, reconstitution, and mutation. Insofar as possible, all three methods are used together. 

We look at E. coli DNA polymerase I as an example of how biochemical and genetic studies are used to characterize a DNA replication enzyme. Then we consider the other major proteins involved in DNA replication in E. coli before examining the proteins that participate in the synthesis of DNA in different types of organisms. 

The surveillance network against DNA damage implies the interaction of PARP-1 with other factors. The interaction of PARP-1 with p53 has been widely described, thus supporrii the existence of cooperarion between these proteins in maintaining genome int fity (see Chapter 6). PARP-1 aas in concert with Werner syndrome protein (WRN), a protein involved in DNA replication and repair, which interacts direedy with PARP-1 and with PCNA. It has been... 

Following gradient purification of virions, LC/MS/MS was used to identify the components of the HCMV virion [6]. The results were verified by coupling high-accuracy mass measurements with LC and FT-ICR (Fourier transform ion cyclotron resonance) MS. Fifty-nine proteins were identified including 12 proteins encoded by known HCMV ORFs not previously known to reside in virions. The classes of proteins identified included capsid proteins, tegument proteins, glycoproteins, and 12 proteins involved in DNA replication and transcription. Additionally, 12 more viral polypeptides were identified that had not been previously characterized [6]. 

Recently it has been proposed that bacterial inactivation by HOCl is the result of inhibition of DNA replication. When bacteria are exposed to HOCl, there is a precipitous decline in DNA synthesis that precedes inhibition of protein synthesis, and closely parallels loss of viability. During bacterial genome replication, the origin of replication (oriC in E. coli) binds to proteins that are associated with the cell membrane, and it was observed that HOCl treatment decreases the affinity of extracted membranes for oriC, and this decreased affinity also parallels loss of viability. A study by Rosen et al. compared the rate of HOCl inhibition of DNA replication of plasmids with different replication origins and found that certain plasmids exhibited a delay in the inhibition of replication when compared to plasmids containing oriC. Rosen s group proposed that inactivation of membrane proteins involved in DNA replication are the mechanism of action of HOCl. 

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