Gene expression associated with DNA-dependent protein kinase activity under normoxia, hypoxia, and reoxygenation

In order to elucidate the mechanism of concerted expression of various proteins related to DNA-dependent protein kinase (PK) activity, we examined the relationship of the expression of these proteins with that of a transcription factor Sp1. We also explored whether the expression of genes related to DNA-PK activity and Sp1 changed after hypoxia and reoxygenation. Reverse transcription-polymerase chain reaction (RT-PCR) was employed to measure expression of various proteins related to DNA-PK activity in peripheral blood cells (PBLs) of normal healthy volunteers and cancer patients. M059K and DLD1 cells were made hypoxic with the hypoxia chamber, and the expression of various proteins in the cells was examined. DNA-PK activity was measured using synthetic peptide substrate mimicking the sequence around Ser15 of human p53. Expression of examined genes whose expression was related to DNA-PK activity was significantly correlated with expression of Sp1. The expression of most genes lost its relationship with the expression of Sp1 after hypoxic exposure and reoxygenation. DNA-PK activity tended to decrease after hypoxic exposure and to recover after reoxygenation. Sp1 may control expression of genes related to DNA-PK activity. Expression of those genes deviated from the control Sp1 under hypoxia and reoxygenation. The control mechanism for expression of genes related to DNA-PK activity under hypoxia and reoxygenation may be different from that under aerobic conditions. (author)