title: CKI isoforms α and ε regulate Star-PAP target messages by controlling Star-PAP poly(A) polymerase activity and phosphoinositide stimulation.
abstract: Star-PAP is a non-canonical, nuclear poly(A) polymerase (PAP) that is regulated by the lipid signaling molecule phosphatidylinositol 4,5 bisphosphate (PI4,5P(2)), and is required for the expression of a select set of mRNAs. It was previously reported that a PI4,5P(2) sensitive CKI isoform, CKIα associates with and phosphorylates Star-PAP in its catalytic domain. Here, we show that the oxidative stress-induced by tBHQ treatment stimulates the CKI mediated phosphorylation of Star-PAP, which is critical for both its polyadenylation activity and stimulation by PI4,5P(2). CKI activity was required for the expression and efficient 3'-end processing of its target mRNAs in vivo as well as the polyadenylation activity of Star-PAP in vitro. Specific CKI activity inhibitors (IC261 and CKI7) block in vivo Star-PAP activity, but the knockdown of CKIα did not equivalently inhibit the expression of Star-PAP targets. We show that in addition to CKIα, Star-PAP associates with another CKI isoform, CKIε in the Star-PAP complex that phosphorylates Star-PAP and complements the loss of CKIα. Knockdown of both CKI isoforms (α and ε) resulted in the loss of expression and the 3'-end processing of Star-PAP targets similar to the CKI activity inhibitors. Our results demonstrate that CKI isoforms α and ε modulate Star-PAP activity and regulates Star-PAP target messages.
authors: Department of Pharmacology, University of Wisconsin-Madison, 1300 University Ave. University of Wisconsin Medical School, Madison, WI 53706, USA.
authors: Rakesh S
authors: RS
authors: Laishram
authors: Christy A
authors: CA
authors: Barlow
authors: Richard A
authors: RA
authors: Anderson
mesh_terms: D048149:Casein Kinase 1 epsilon / Q000378:metabolism*; D048128:Casein Kinase Ialpha / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D009713:Nucleotidyltransferases; D018384:Oxidative Stress; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010766:Phosphorylation; D026723:Polyadenylation; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D006873:Hydroquinones; D019269:Phosphatidylinositol 4,5-Diphosphate; D012333:RNA, Messenger; C018855:2-tert-butylhydroquinone; D048149:Casein Kinase 1 epsilon; D048128:Casein Kinase Ialpha; D009713:Nucleotidyltransferases; C586325:TUT1 protein, human; D011062:Polynucleotide Adenylyltransferase