FIG. 3.
Effects of oxygen on the expression of COX5a and COX5b. Northern blot of total RNA isolated from cells grown in 200 μM O2 (air) (lane 1), 50 μM O2 (lane 2), 5 μM O2 (lane 3), 0.5 μM O2 (lane 4), 0.2 μM O2 (lane 5), and oxygen-free N2 (lane 6). The RNA was hybridized with probes specific for COX5a, COX5b, and ACT1, as described in Materials and Methods. The ACT1 gene was probed as a control for RNA load. The levels of COX5a and COX5b mRNAs, normalized to the ACT1 mRNA, are presented as decimal percentages relative to their levels in air (for COX5a) or nitrogen (for COX5b).