Distinctive activities of DNA polymerases during human DNA replication.
The contributions of human DNA polymerases (pols) alpha, delta and epsilon during S-phase progression were studied in order to elaborate how these enzymes co-ordinate their functions during nuclear DNA replication. Pol delta was three to four times more intensely UV cross-linked to nascent DNA in late compared with early S phase, whereas the cross-linking of pols alpha and epsilon remained nearly constant throughout the S phase. Consistently, the chromatin-bound fraction of pol delta, unlike pols alpha and epsilon, increased in the late S phase. Moreover, pol delta neutralizing antibodies inhibited replicative DNA synthesis most efficiently in late S-phase nuclei, whereas antibodies against pol epsilon were most potent in early S phase. Ultrastructural localization of the pols by immuno-electron microscopy revealed pol epsilon to localize predominantly to ring-shaped clusters at electron-dense regions of the nucleus, whereas pol delta was mainly dispersed on fibrous structures. Pol alpha and proliferating cell nuclear antigen displayed partial colocalization with pol delta and epsilon, despite the very limited colocalization of the latter two pols. These data are consistent with models where pols delta and epsilon pursue their functions at least partly independently during DNA replication.
Rytkönen
Anna K
AK
Biocenter Oulu and Department of Biochemistry, University of Oulu, Finland.
Vaara
Markku
M
Nethanel
Tamar
T
Kaufmann
Gabriel
G
Sormunen
Raija
R
Läärä
Esa
E
Nasheuer
Heinz-Peter
HP
Rahmeh
Amal
A
Lee
Marietta Y W T
MY
Syväoja
Juhani E
JE
Pospiech
Helmut
H
D002843:Chromatin / Q000737:chemistry; D004256:DNA Polymerase I / Q000737:chemistry; D004257:DNA Polymerase II / Q000737:chemistry; D004258:DNA Polymerase III / Q000737:chemistry; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D016253:Microscopy, Immunoelectron; D008898:Mimosine / Q000494:pharmacology; D016196:S Phase; D014466:Ultraviolet Rays
D002843:Chromatin; D008898:Mimosine; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase