The dual Ser2p-CTD of Pol II is generated by CDK9. (A) A375 cells treated with Flavopiridol at 0.0 µM, 0.3 µM, and 1 µM for 24 h, (Top) shows cell extract blot. (Lower) Ser2p-CTD blot of MBP-N-JMJD5 pulldown from the above three groups. (B) HEK293 cells treated with Flavopiridol at 0.0 µM, 0.1 µM, and 0.3 µM for 24 h. (Top) shows cell extract blot. (Lower) Ser2p-CTD blot of MBP-N-JMJD5 pulldown from the above three groups. (C) A375 cells treated with Thal-SNS-032 at 0 nM, 100 nM, and 300 nM, respectively, for 4 h. (Top) shows cell extract blot. (Lower) Ser2p-CTD blot of MBP-N-JMJD5 pulldown from the 0 nM and 300 nM Thal-SNS-032 group. (D) HEK293 cells treated with Thal-SNS-032 at 0 nM, 30 nM, and 100 nM, respectively, for 4 h. (Top) shows cell extract blot. (Lower) Ser2p-CTD blot of MBP-N-JMJD5 pulldown from the 0 nM and 100 nM Thal-SNS-032 group.