DNA synthesis on UV irradiated model templates using human DNA polymerases alpha and beta: primer slippage to account for evident transdimer continuity in product

We have studied the comparative behavior of human DNA polymerases alpha and beta on a polynucleotide template of dT100 with dA15 covalently attached at the 3' end to serve as primer when defined numbers of pyrimidine dimers are introduced by UV (254 nm) irradiation. We have obtained the surprising result that with both alpha and beta polymerases the incorporation of labelled dATP is enhanced when the template has been irradiated (maximum value at 1000 J/m2 UV incident dose). In the presence of Mn2+, DNA polymerase beta produces a product size corresponding to full copying of the template whether irradiated or not. In marked contrast DNA polymerase alpha produces only short products on unirradiated strands but full copying of irradiated templates. Evidently both polymerases utilize a much larger fraction of the template pool following UV irradiation.

Preparation and preliminary characterization of monoclonal antibodies against human DNA polymerase alpha

We report the successful establishment of 16 stable murine hybridoma monoclones that produce homogeneous antibodies against KB cell DNA polymerase alpha. All of the antibodies exhibit specific binding of polymerase alpha activity, and 3 of them possess anti-polymerase alpha neutralizing activity. None of the antibodies interacts detectably with KB cell DNA polymerases beta or gamma. All of the 5 antibodies so far examined demonstrate linear Scatchard binding plots and very high binding affinities, with equilibrium dissociation constants (Kd) ranging between 3.2 x 10(-9) and 3.4 x 10(-10) M. These monoclonal antibodies comprise a set of powerful and specific reagents that should facilitate the development and application of novel approaches to the complex biochemical mechanisms of mammalian DNA replication.

Intracellular localization of human DNA polymerase alpha with monoclonal antibodies

We have successfully established 16 stable murine hybridomas that secrete monoclonal antibodies specific for human DNA polymerase alpha. The results of immunocytochemical studies, using 4 of these monoclonal antibodies and immunoperoxidase detection methods, document the exclusively intranuclear localization of DNA polymerase alpha in three separate lines of cultured human cells. By light microscopy, the immunoperoxidase reaction product exhibits a diffuse pattern of distribution within the nucleoplasm, but nucleoli are clearly negative. In cultures of the transformed lines, KB nd BeWo, more than 955 of the cells are positive, suggesting that intranuclear DNA polymerase alpha antigens persist throughout the mitotic cycle. In striking contrast, in the normal diploid fibroblast line, WI-38, a smaller fraction of the cultured cells is positive, and there is no detectable polymerase alpha antigen in the closely apposed cells of microcolonies that are presumed to be contact-arrested and no longer mitotically cycling. In cells in mitosis that have dissolved their nuclear envelopes (and are thus transiently anucleate), the anti-polymerase alpha reaction continues to be strongly positive, and in this single circumstance the reaction product is diffusely distributed throughout the cell cytoplasm. Initial electron microscopic examination of KB cells confirms and extends these observations. The immunoperoxidase reaction product is essentially limited to the nuclear compartment and is predominantly distributed in the midzonal region of the nucleoplasm between centrally disposed nucleoli and peripherally located blocks of condensed chromatin.

Bone-seeking properties of Tc-99m carbonyl diphosphonic acid, dihydroxy-methylene diphosphonic acid and monohydroxy-methylene phosphoinic acid: concise communication

Carbonyl diphosphonic acid, dihydroxy-methylene diphosphonic acid and monohydroxy-methylene diphosphonic acid were synthesized and labeled with Tc-99m. Their chemical structures were confirmed and their bone-seeking relationships were compared with those of Tc-99m MDP in experimental animals. MKonohydroxy-methylene diphosphonic acid was found to have higher bone affinity and faster blood clearance than MDP, whereas carabonyl diphosphonic acid and dihydroxy-methylene diphosphonic acid demonstrated lower bone affinity and slower blood clearance than MDP.

A study of the relationship between chemical structure and bone localization of Tc-99m diphosphonic acids: concise communication

The study was undertaker to evaluate the effect on bone localization of substitutions at the bridge carbon atom of methylenediphosphonic acid. Two monosubstituted compounds (ethylidenediphosphonic acid and benzylmethylenediphosphonic acid), and one disubstituted compound (isopropylidenediphosphonic acid), were synthesized. The biological behavior was compared with that of MDP and dichloro-MDP in the rat, using Tc-99m as a label. Ethylidenediphosphonic acid showed the highest femur-to-liver and femur-to-muscle ratios. MDP exhibited a slightly faster blood clearance than ethylidenediphosphonic acid.

Enzymological characterization of DNA polymerase alpha. Basic catalytic properties processivity, and gap utilization of the homogeneous enzyme from human KB cells

This report describes the results of our initial enzymological characterization of a homogeneous preparation of DNA polymerase alpha that we have purified from cultured human KB cells. Although the enzyme is most reactive with duplex DNA substrates that contain short gaps (optimally activated) in incubations that require Mg2+, the polymerase possesses the intrinsic capacity to copy the initiated ribohomopolymer template, (A)-n, (dT)-200, at low rates in the presence of Mn2+. Because of the preponderance of DNA polymerase alpha in actively multiplying vertebrate cells, it is probable that this low level of activity comprises the majority of the ribopolymer copying activity that can be detected in crude tissue extracts. The presence of contaminating or associated deoxyribonuclease activities can be excluded from the purified enzyme to levels of 10(-4) to 10(-7) of the polymerase activity. The mechanism of polymerization on activated DNA under optimum conditions is moderately processive, with 11 +/- 5 nucleotides incorporated per polymerization cycle. The polymerase is unable to work at nicks or at short gaps of approximately 20 to 30 nucleotides in length, and it measures a surprisingly invariant effective template length on optimally activated DNA and on DNA molecules that have been gapped to varying extents with Escherichia coli exonuclease III. In the "Appendix" we present an amplification of the theoretical formulation of Bambara et al. (Bambara, R. A., Uyemura, D., and Choi, T. (1978) J. Biol. Chem. 253, 413--423) that permits the use of DNA polymerases with significant associated 3' leads to 5'-exonuclease activities for the accurate measurement of average template lengths (gap sizes) and titration of usable 3'-hydroxyl primer termini in gapped, duplex DNA substrates.

Synthesis, radiotechnetium labelling, and comparison of biologic behavior of longer-chain analogs of methylene diphosphonate

Polymethylene diphosphonic acids of different chain lengths ( n = 2, 3, and 10) were synthesized and labeled with technetium-99m. Their biologic behavior was compared with that of Tc-99m-labeled methylene diphosphonate (MDP) in experimental animals. With n = 2 (ethylene diphosphonic acid), the compound resembled MDP in bone affinity. The longer-chain analogs had lower bone affinity.

Altered body distribution of [99mTc] pertechnetate in iatrogenic hyperaluminemia

Failure of intravenously administered [99mTc] pertechnetate to leave the vascular space was observed in a patient with hyperaluminemia due to treatment with an antacid drug containing aluminum hydroxide. A repeat study 3 mo after discontinuing medication, when the plasma aluminum level had fallen, revealed normal in vivo distribution of pertechnetate. It was found that instant thin-layer chromatography, using pertechnetate and an 85% methanol system, can detect plasma aluminum levels as low as 50 microgram/l.

In vitro replication of mitochondrial DNA. Elongation of the endogenous primer sequence in D loop mitochondrial DNA by human DNA polymerase beta

Whe incubated in the presence of Mn2+ as the divalent metal activator, highly purified human DNA polymerase beta performs a selective and limited replication of KB cell closed circular mtDNA. On the basis of biochemical and electron microscopic analyses of the reaction product, we demonstrate that the polymerase specifically recognizes and elongates the 9 S primer sequence in D loop mtDNA and then proceeds to copy the displaced strand. The point at which the enzyme switches template strands is most likely that at which all negative superhelical turns have been removed and an energetically unfavorable introduction of positive superhelical turns would be required for further synthesis on the initial parental template strand. The product of the reaction is an enlarged D loop that has been converted to a duplex structure. This is the first description of the capacity of a pure eukaryotic DNA polymerase to replicate a naturally occurring, specifically initiated duplex DNA molecule. Our results suggest that this system may be particularly useful in developing an in vitro duplex circular DNA replication system with purified eukaryotic components.

Nuclear deoxyribonucleic acid polymerase. Further observations on the structure and properties of the enzyme from human KB cells

At low ionic strength KB cell DNA polymerase N1 forms large aggregates of a size comparable to those of DNA polymerase C. However, in contrast to polymerase C, the polymerase N1 aggregate: (a) retains the distinctive features of the polymerase N1 monomer, specifically its relative insensitivity to salt and to p-hydroxymercuribenzoate, and its pI of 9.3; and (b) is quantitatively converted to the polymerase N1 monomer form at appropriate ionic strength. It is important to recognize that since both polymerase N1 and polymerase C undergo salt-dependent association-dissociation reactions, attempts to distinguish these clearly indedependent polymerase species on the basis of size criteria can be very misleading. This is particularly true in relatively impure enzyme fractions that are generally isolated from eukaryotic tissue sources in low ionic strength buffers. We had earlier reported (Wang, T. S.-F., Sedwick, W. D., and Korn, D. (1974) J. Biol. Chem. 249,841-850; Sedwick, W. D., Wang, T. S.-F., and Korn, D. (1972) J. Biol. Chem. 247,5026-5033; Sedwick, W. D., Wang, T. S.-F., and Korn, D. (1974) Methods Enzymol. 29, 89-102) that DNA polymerase N1 could not utilize homoribopolymer templates. We have re-examined this question with a modified and more stringent method of product assay, and we show here that a greater than or equal 95% homogeneous preparation of polymerase N1 can copy the primer-template (A)n-(dT)-/16 at about one-half the rate that it copies activated DNA under optimum incubation conditions.