FIGURE 5.

SO stimulates bypass activity of Pol η. CPD bypass activity of recombinant Pol η (A) or endogenous native enzyme immunoprecipitated from human cells in culture (B) was monitored using P/T2 DNA substrate in the absence or presence of 8 μm sphingosine as described under “Experimental Procedures.” The control template contained two tandem dT residues instead of the lesion; the sequence was identical otherwise. S, substrate (−) enzyme.