Zebrafish experiments were approved by the Institutional Animal Care and Use Committee of Tongji University. Embryos were raised at 28°C in E3 solution. MOs were obtained from Gene Tools. Sequences of MOs are listed as follows: hexim1, 5′-TAATAAGCTCCATAACTGCACACTC-3′ (43); pkd2, 5′-AGGACGAACGCGACTGGAGCTCATC-3′ (24); and a standard control, 5′-CCTCTTACCTCAGTTACAATTTATA-3′. For rescue experiments, 200 pg of human HEXIM1 mRNA or HEXIM1 S158E mRNA was co-injected with pkd2 MO and hexim1 MO into one-cell–stage embryos. For total lysates, embryos were deyolked and homogenized completely in 2× SDS-loading buffer and then boiled for 10 min. For IP, embryo lysates were prepared in NP-40 buffer. Lysates were then incubated at 4°C with GFP-Trap, followed by Western blotting analysis.