Fig. 4.

Model for signal mediated regulation of Star-PAP to differentially control the 3′-end processing of distinct target messages. Various signal transduction components integrate into the Star-PAP 3′-end processing complex downstream of the signalling pathway, to regulate different target genes. In this model, casein kinase (isoforms α and ε) works downstream of oxidative stress to specifically regulate stress response genes HO-1 and NQO-1 through Star-PAP. On the other hand, PKCδ works in concert with DNA damage signal to regulate proapoptotic gene BIK through Star-PAP. The PKCδ mediated pathway is independent of oxidative stress regulation and vice versa. Thus, Star-PAP acts as a central regulatory molecule at the 3′-end of a gene that differentially controls the expression of target genes through various kinases and signalling molecules.