Figure 2.

Nucleoside transport in SUPKO compared to Cas9 cells. (A) Uptake of 0.1 µM [³H]-adenosine was >99% reduced in SUPKO compared to Cas9 (0.00046 ± 0.00002 vs. 0.082 ± 0.004 pmol(10⁷ cells)⁻¹s⁻¹ (both r² > 0.99; p < 0.0001). The uptake in SUPKO was still significantly non-zero over 60 s (p < 0.0001). (B) 100 nM [³H]-uridine was taken up robustly by cas9 cells, but significantly less in SUPKO (p < 0.0001; 0.10 ± 0.003 vs. 0.0014 ± 0.00009 pmol(10⁷ cells)⁻¹s⁻¹ (r² = 0.997 and 0.989, respectively). Uptake in SUPKO was significantly non-zero (p = 0.0005). (C) Uptake of 50 nM [³H]-thymidine was lower in SUPKO than in cas9 cells (p = 0.0003; 8.7 × 10⁻⁵ ± 1.2 × 10⁻⁵ vs. 0.0018 ± 0.0001 pmol(10⁷ cells)⁻¹s⁻¹ (r² = 0.962 and 0.988, respectively). The residual thymidine uptake in SUPKO was significantly non-zero (p = 0.019). (D) Uptake of 0.1 µM [³H]-guanosine was different in Cas9 and SUPKO cells (p < 0.0001; 0.010 ± 0.0006 vs. 0.00046 ± 0.00011 pmol(10⁷ cells)⁻¹s⁻¹; r² = 0.98 and 0.78, respectively). Residual guanosine uptake in SUPKO was significantly non-zero (p = 0.0085). (E) Uptake of 100 µM [³H]-hypoxanthine was lower in SUPKO than in cas9 cells. The rates were not significantly different over 3 experiments by unpaired t-test, but in the experiment shown, the difference between the two linear regression lines was significant on F-test (GraphPad Prism 9), p = 0.0068). (F) Uptake of 100 nM [³H]-uracil was identical in SUPKO and cas9 cells (0.00032 ± 0.00003 vs. 0.00031 ± 0.00002 pmol(10⁷ cells)⁻¹s⁻¹, n = 3; p = 0.81). One representative experiment in triplicate is shown.