Nucleic Acids Research, 1989, Vol. 17, No. 12 4757-4767
© 1989
ENZYMOLOGY |
Contribution of DNA polymerase 
to DNA replication in permeable CHO cells synchronized in S phase
Department of Metabolic Regulation, Boston Biomedical Research Institute 20 Staniford Street, Boston, MA 02114 USA and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School Boston, MA 02115, USA
*To whom correspondence should be addressed
Received March 6, 1989. Revised May 19, 1989. Accepted May 19, 1989.
To evaluate the relative contributions or DNA polymerase 
and DNA polymerase 
in chromosome replication during the S phase of the cell cycle, we have used the permeable cell system for replication as a functional assay. We carried out the analysis of DNA polymerases both in quiescent cells stimulated to proliferate and progress through the cell cycle (monolayers) and in actively growing cells separated into progressive stages of the cell cycle by centrifugal elutriation (suspension cultures). DNA polymerase was measured by using the inhibitor butylphenyl dGTP at low concentrations. Using several inhibitors such as aphidicolin, ddTTP and butylphenyl dGTP, we found that DNA polymerase and activity were coordinately increased during S phase and declined at the end. However, DNA polymerase was performing about 80% of the total replication and DNA polymerase performed only 20%. This high ratio of DNA polymerase to DNA polymerase replication activity was maintained throughout S phase in two entirely different experimental approaches.
+present address: Institute of Biochemistry, Department I, Semmelweis University Medical School, Budapest 1444, Budapest 8, Hungary
On leave of absence: Institute of Biological and Medical Chemistry, AMS USSR, Pogodinskaia 10, 119121 Moscow, USSR