Effect of hyperthermia on CHO DNA polymerases. cap alpha. and. beta

Journal Article · Fri Jan 01 04:00:00 EST 1982 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3575691· OSTI ID:5572192

Spiro, I J; Denman, D L; Dewey, W C

The heat sensitivity of polymerase ..beta.. (pol-..beta..) has been studied in a an attempt to assess the molecular lesions for heat killing and heat radiosensitization. Viable cells were heated, and then polymerase activity was determined in crude cell extracts by measuring the incorporation of (/sup 3/H) TMP into an exogenous, activated calf thymus DNA. The thermal inactivation of pol-..beta.. activity was shown to correlate with hyperthermic cell killing and radiosensitization. Pol-..beta.. activity decreased exponentially when cells were heated at temperatures of 43/sup o/C and above, and a 10-min 45.5/sup o/C heat shock reduced pol-..beta.. activity by 80%. Also, pol-..beta.. activity showed a 3-fold greater heat sensitivity than polymerase ..cap alpha.. (pol-..cap alpha..) activity at 43.5 and 45.5/sup o/C. When cells were heated at temperatures of 42.2-42.5/sup o/C, pol-..beta.. activity decreased, but as for cell killing, tollerance to any further treatment was observed after 2 hr of heating. Thermal tolerance also was observed as a decrease in the rage of pol-..beta.. inactivation at 45.5/sup o/C if cells were given either a preconditioning heat treatment at 42.2/sup o/C for 6 hr, or 45.5/sup o/C for 10 min followed by 24 hr at 37/sup o/C. Furthermore, when cells were heated at 42.2/sup o/C in the presence of 7 mM procaine-HCl, both cell killing and loss of pol-..beta.. activity were greatly enhanced. Finally, the return of pol-..beta.. activity after thermal treatment correlated with the decrease in radiosensitization as evidenced by an increase in survival as a treatment (10 min, 45.5/sup o/C) and subsequent X-ray treatment were separated by increasing amounts of time at 37/sup o/C. For example, during incubation at 37/sup o/C after heat treatment, pol-..beta.. activity and the logarithm of survival increased over 4-fold, while pol-..cap alpha.. activity increased only 1.4-fold to 75% of its control activity.

• Research Organization: Colorado State Univ., Fort Collins
• OSTI ID: 5572192
• Journal Information: Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 89:1; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

560111* -- Radiation Effects on Biochemicals-- In Vitro-- (-1987)
560201 -- Thermal Effects-- Cells-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BODY TEMPERATURE
DNA
ELECTROMAGNETIC RADIATION
ENZYMES
HYPERTHERMIA
IONIZING RADIATIONS
LABELLED COMPOUNDS
NUCLEIC ACIDS
NUCLEOTIDYLTRANSFERASES
ORGANIC COMPOUNDS
PHOSPHORUS-GROUP TRANSFERASES
POLYMERASES
RADIATION EFFECTS
RADIATIONS
RADIOSENSITIVITY
TEMPERATURE EFFECTS
TRANSFERASES
TRITIUM COMPOUNDS
X RADIATION