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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: Adv Biol Regul. 2012 Oct 13;53(1):64–76. doi: 10.1016/j.jbior.2012.10.004

Fig. 2.

Fig. 2

PIPKIα and PI4,5P2 regulation of Star-PAP activation. PIPKIα activation and PI4,5P2 generation could activate Star-PAP through four potential mechanisms under different conditions. ① Activation of the locally targeted PIPKIα within a PIP-containing compartment generates PI4,5P2, which in turn participates the conformational changes of the Star-PAP complex and facilitates the recruitment of PKCδ and other activating enzymes. ② The locally generated PI4,5P2 stimulates Star-PAP activation together with other co-factors. ③ PI4,5P2 directly activates PKCδ, which phosphorylates and enhanced Star-PAP activities required for mRNA processing. ④ The nuclear PLCs or PI3K processes PI4,5P2 and generates second messengers that are in involved in additional signaling events for Star-PAP activation.