Fig. 6. CCR4 is an ssDNA exonuclease. (A) Time course of CCR4-FLAG enzyme activity with the ssDNA substrate containing five As at its 3′ end. A 160 ng aliquot of CCR4-FLAG and of ccr4-1-FLAG was used in the incubations. (B) ccr4 mutations block CCR4 ssDNA exonuclease activity. A 32 ng aliquot of each CCR4-FLAG variant was used and the reactions were for 60 min.