Presence Of DNA Polymerase Research Articles

DNA Polymerase Activity in Human Serum: Studies with Australia Antigen

SummaryThe presence of DNA polymerase in normal human serum and its possible association with Australia antigen was investigated. DNA polymerase activity was determined in 135 samples of normal serum. Only 3 samples revealed appreciable amounts of activity. The addition of a variety of polynucleotide templates did not stimulate polymerase activity.Australia antigen is a particle associated with hepatitis and is reported to contain RNA. A DNA polymerase, “reverse transcriptase” might be required for replication of this RNA. We found DNA polymerase activity in only one of five preparations of purified Australia antigen. A similar activity was also found to be present in serum from certain normal volunteers. In either case, polymerase activity does not require nor is it stimulated by added polynucleotides suggesting that the enzyme may already be associated with a template such as RNA or DNA. A comparison between the amount of DNA polymerase activity in serum and the presence of Australia antigen in three se...

Preliminary investigation of poly (dA-dT) conformation and of its interaction with DNA polymerase

Conformation changes of poly (dA-dT) under various conditions of temperature, solvent, and in the presence of DNA polymerase from Micrococcus luteus, were investigated by means of circular dichroism. The interaction of poly (dA-dT) with these proteins is reflected in spectral changes, which indicates the stabilization of the secondary structure towards an ordered form, and which characterizes poly (dA-dT) at low temperature and high ionic strength. This form can be considered to be similar to the B form. Under the influence of an increasing concentration of ethylene glycol, poly (dA-dT), at low temperature, adopts different conformations when compared to its complex with proteins, and which is interpreted to be similar to the C form. Preliminary study of the interaction DNA-DNA polymerase shows the appearance of conformational changes when the complex is formed, and suggest the stabilization of AT rich regions.

Studies on polynucleotides: LXIX. Synthetic deoxyribopolynucleotides as templates for the DNA polymerase of Escherichia coli: DNA-like polymers containing repeating trinucleotide sequences

Short-chain deoxyribopolynucleotides containing repeating trinucleotide sequences serve as templates for the DNA-polymerase-catalyzed polymerization of deoxyribonucleoside triphosphates. The products are double-stranded DNA-like polymers containing, in both of the complementary strands, repeating trinucleotide sequences which were present in the short-chain templates. Four DNA-like polymers were thus prepared: poly dTTC:dGAA, poly dTTG:dCAA, poly dTAC:dGTA and poly dATC:dGAT. In every case, it was necessary to use as the templates, short segments of chain length 9 to 15 nucleotide units corresponding to both of the complementary strands of the desired DNA-like polymer. All of the polymers were shown to contain repeating trinucleotide sequences by comprehensive nearest-neighbor frequency analyses. Three of the four DNA-like polymers effectively served as templates for the synthesis of more of the same polymer in the presence of DNA-polymerase. Characterization of the DNA-like polymers with respect to molecular weight and buoyant density in a cesium chloride density-gradient is described in an accompanying paper.

Deoxyribonucleic acid polymerase in L cells: I. Properties of the enzyme and its activity in synchronized cell cultures

1. 1. The presence of DNA polymerase (deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7) has been demonstrated in L cells grown in culture and its properties have been studied. 2. 2. This DNA polymerase has been purified approximately 15-fold with respect to the protein of the crude extracts. 3. 3. The activity of crude extracts as well as that of partially purified preparations has been shown to be almost entirely dependent on the presence of a denatured DNA primer. For full activity of the purified preparation, all four deoxyribonucleoside triphosphates and Mg 2+ were also necessary. 4. 4. When DNA synthesis in L cells was inhibited in vivo, the DNA polymerase activity of cell extracts increased. When the inhibition was reversed, and DNA synthesis was reinitiated, the activity of the enzyme decreased. 5. 5. The observed changes in the activity of DNA polymerase are postulated to be due to altered intracellular states of the enzyme.

The incorporation of ribonucleotides into terminal positions of deoxyribonucleic acid

A DNA-rich preparation from calf-thymus nuclei has been shown to catalyze the incorporation of ribonucleoside triphosphates into DNA. All four ribonucleoside triphosphates can serve as precursors in the reaction, with the following order of activity: GTP > CTP > ATP > UTP. The incorporated ribonucleotide forms the nucleoside terminus of the DNA chain to which it is attached. The addition of the complementary ribonucleoside or deoxyribonucleoside triphosphates does not stimulate incorporation of the labeled precursor. The presence of DNA polymerase which has also been demonstrated to occur in this enzyme fraction does not appear to influence the reaction.