FIG. 3.

Failure to accumulate endogenous ROS results in a late G₁ cell cycle arrest due to the absence of cyclin A protein. (A) T98G cells serum starved and restimulated with 5% FBS and either untreated or treated with antioxidants were assayed for pRb phosphorylation; cyclin D, cyclin E, and cyclin A kinase activity; Cdk2 phosphorylation status (immunoprecipitation, Cdk2; blotting, Cdk2); and levels of Cdk inhibitors p27 and p21. (B) Serum-starved and restimulated T98G cells either untreated or treated with tempol were examined at 16 h (late G₁) and 20 h (late G₁/S phase) as follows: for cyclin A, DHFR, and actin mRNA levels by reverse transcription-PCR; for cyclin A RNA levels by Northern blotting; and for cyclin A and actin protein levels by immunoblotting.