Do DNA polymerases δ and α act coordinately as leading and lagging strand replicases?

Abstract

The activity ratio of DNA polymerases J and a in calf thymus was found to be invariably 1:1, irrespective of extraction procedure (8 types) and subcellular localization (cytoplasm, nucleus and microsomes). This was established by separation of the two forms by hydroxyapatite chromatography and by their response to specific inhibitors and monoclonal antibodies. This finding supports the dimeric DNA polymerase model [(1980) J. Biol. Chem. 255, 4290-4303], which proposes that DNA polymerases J and at act coordinately as leading and lagging strand enzymes, respectively, at the replication fork.

Characteristics of DNA replication in isolated nuclei initiated by an aprotinin‐binding protein

“…These results suggest that replication in isolated nuclei is mediated by a complex containing both polymerases and that antibodies that bound to either component could interfere with replication mediated by that complex. This appears to be the case in intact cells, as active replication complexes containing both enzymes have been isolated from such systems [Focher et al, 1988; Sabatino et al, 19881. In addition, DMSO progressively inhibits DNA polymerase 01 while concentrations of DMSO from 2-10% significantly stimulate DNA polymerase 6 [Lee and Toomey 19861.…”

“…These results suggest that replication in isolated nuclei is mediated by a complex containing both polymerases and that antibodies that bound to either component could interfere with replication mediated by that complex. This appears to be the case in intact cells, as active replication complexes containing both enzymes have been isolated from such systems [Focher et al, 1988; Sabatino et al, Several lines of evidence argue that damaged DNA is not a significant initiation point for the observed replication. First, both aprotinin and the cytosolic ADR inhibitor block nuclear incor-poration but have no effect on incorporation directed by nuclease-treated calf thymus DNA.…”

Misincorporation of Uracil Into DNA as Possible Contributor to Neuronal aging and Abiotrophy

“…Work carried out in author's laboratory based upon the use of aphidicolin, a specific inhibitor of DNA polymerases cx and 6 (Pedrali-Noy & Spadari, , Spadari et al, 1982 or upon unique properties of brain neurons which contain organelles that harbor a single DNA polymerase such as nuclei from adult riondividing neurons (DNA polymerase b), and synaptosomal mitochondria (DNA polymerase y), have successfully contributed to the elucidation of physiological functions of eukaryotic DNA polymerases (Hiibscher et al, 1977(Hiibscher et al, , 1978(Hiibscher et al, , 1979Waser et al, 1979. Thus, DNA polymerases IX and 6 play a major role in nuclear DNA replication (Hubscher et al, 1978, 1989Focher et al, 1988Focher et al, , 1989, DNA polymerase p is involved in nuclear DNA repair (Hiibscher et al, 1979, Waser et al, 1979 and DNA polymerase y is responsible for the mitochondrial DNA replication (Hiibscher et al, 1979). The disappearance of DNA polymerases IX and 6 in postnatal neurons and the presence of only DNA polymerases p and y (Hiibscher et al, 1977(Hiibscher et al, , 1978(Hiibscher et al, , 1979Waser et al, 1979) correlate well with the fact that at the birth neurons stop replicative DNA synthesis whereas they need nuclear reparative DNA synthesis and mitochondrial DNA replication.…”

Initiation of lymphocyte DNA synthesis

“…Finally, ADR-mediated 3H-dTTP incorporation is completely blocked by antibodies to PCNA [27], a protein which specifically associates with DNA polymerase delta and greatly increases the processivity of the enzyme in replicating the leading DNA strand [10,111. Current evidence indicates that most eukaryotic DNA repair is performed by DNA polymerase beta, with perhaps some contribution by DNA polymerase alpha, but that DNA polymerase delta is active only in DNA replication [6,13,14,28].A second concern was that ADR activity was simply one or more of the DNA polymerase enzymes, which are found primarily in the cytosolic fraction when cells are homogenized by mechanical disruption or solubilized by detergent. This was not easily resolved, as ADR activity requires DNA polymerase activity; thus inhibitors of the latter also inhibited the former.…”

“…The complex of proteins which contains the polymerases and mediates DNA strand replication is termed the replisome 151. Among the replisome constituent proteins are DNA polymerase delta [6][7][8], which replicates the leading strand DNA; PCNA (proliferating cell nuclear antigen), which is a processivity factor for DNA polymerase delta [9-111; DNA polymerase alpha, which replicates the lagging DNA strand [12][13][14]; DNA primase, which synthesizes the RNA primer required for DNA polymerase alpha [ 15,161; and an associated helicase activity which unwinds the DNA double helix at the replication fork [ 171. The eukaryotic replisome undoubtedly contains many more components, considering that the prokaryotic replisome contains over 20 identified proteins.…”