Functions of DNA Polymerases

This function of the enzyme cleaves the incorrect aminoacyl-tRNA to yield free amino acid and tRNA. This process is analogous to the editing by the 3 -5 exonucleolytic function of DNA polymerases that goes on during DNA synthesis. Like that process, aminoacyl-tRNA editing causes a futile cycle in which the enzyme synthesizes a bond by using energy and then breaks it down. In both... 

While the replacement DNA synthesis method for 3 -end labeling requires both the 3 - 5 exonuclease and DNA polymerase functions of DNA polymerases, the activity of the 5 - 3 DNA polymerase alone is sufficient to produce radiolabeled blunt-ended DNA frj ents with substrates containing protruding 5 termini. For example, the recessed 3 terminus shown in Fig. 1C can be extended by DNA polymerase in the presence of dXTP and dCTP to yield the blunt-ended DNA fragment indicated. 

In this review we summarize the general architecture of DNA polymerases and the chemistry of the DNA polymerase and 3 -5 exonuclease activities (see also DNA replication). The ultimate function of DNA polymerases is the duplication of genetic material, and therefore, we also describe how Pol III functions at a replication fork. Lastly, we present a brief overview of the different repair reactions in which the remaining DNA polymerases act. 

Bertocci B, De Smet A, Weill JC, Reynaud CA. Nonoverlapping functions of DNA polymerases mu, lambda, and terminal de-oxynucleotidyltransferase during immunoglobuhn V(D)J recombination in vivo. Immunity 2006 25 31 1. 

Azathioprine/6-MP are a source of thioguanine nucleotides, which incorporate into DNA, yielding abnormal DNA that, in turn, interferes with the function of DNA polymerases, ligases, and endonucleases. 

A FIGURE 23-24 Schematic model of the proofreading function of DNA polymerases. All DNA polymerases have a similar three-dimensional structure, which resembles a half-opened right hand. The "fingers" bind the single-stranded segment of the template strand, and the polymerase catalytic activity (Pol) lies in the junction between the fingers and palm. 

The two primary functions of DNA polymerase are to read a template DNA strand and catalyze the polymerization of a new daughter strand, and to proofread the newly synthesized strand and correct any errors by removing the incorrectly inserted nucleotide and adding the proper one. 3 -TACGCCGATCTTATAAGGT-5 ... 

Maintenance of the integrity of chromosomal DNA is essential for the survival of all forms of life. In part this is achieved through the proofreading function of DNA polymerases. However, errors in DNA polymerization occasionally escape this proofreading, and the sequence of bases in the DNA is altered by agents that are present in a cell or in its external environment. Both prokaryotes and enkaryotes have evolved elaborate DNA repair mechanisms to correct errors in the sequence of bases in DNA. 

Bebenek K, Kunkel TA (2004) Functions of DNA polymerases. Adv Protein Chem 69 137-65... 

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