IKKalpha regulates mitogenic signaling through transcriptional induction of cyclin D1 via Tcf.
The Wnt/beta-catenin/Tcf and IkappaB/NF-kappaB cascades are independent pathways involved in cell cycle control, cellular differentiation, and inflammation. Constitutive Wnt/beta-catenin signaling occurs in certain cancers from mutation of components of the pathway and from activating growth factor receptors, including RON and MET. The resulting accumulation of cytoplasmic and nuclear beta-catenin interacts with the Tcf/LEF transcription factors to induce target genes. The IkappaB kinase complex (IKK) that phosphorylates IkappaB contains IKKalpha, IKKbeta, and IKKgamma. Here we show that the cyclin D1 gene functions as a point of convergence between the Wnt/beta-catenin and IkappaB pathways in mitogenic signaling. Mitogenic induction of G(1)-S phase progression and cyclin D1 expression was PI3K dependent, and cyclin D1(-/-) cells showed reduced PI3K-dependent S-phase entry. PI3K-dependent induction of cyclin D1 was blocked by inhibitors of PI3K/Akt/IkappaB/IKKalpha or beta-catenin signaling. A single Tcf site in the cyclin D1 promoter was required for induction by PI3K or IKKalpha. In IKKalpha(-/-) cells, mitogen-induced DNA synthesis, and expression of Tcf-responsive genes was reduced. Reintroduction of IKKalpha restored normal mitogen induction of cyclin D1 through a Tcf site. In IKKalpha(-/-) cells, beta-catenin phosphorylation was decreased and purified IKKalpha was sufficient for phosphorylation of beta-catenin through its N-terminus in vitro. Because IKKalpha but not IKKbeta induced cyclin D1 expression through Tcf activity, these studies indicate that the relative levels of IKKalpha and IKKbeta may alter their substrate and signaling specificities to regulate mitogen-induced DNA synthesis through distinct mechanisms.
Albanese
Chris
C
The Albert Einstein Cancer Center, Division of Hormone-Dependent Tumor Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Wu
Kongming
K
D'Amico
Mark
M
Jarrett
Christy
C
Joyce
David
D
Hughes
Julian
J
Hulit
James
J
Sakamaki
Toshiyuki
T
Fu
Maofu
M
Ben-Ze'ev
Avri
A
Bromberg
Jacqueline F
JF
Lamberti
Carmela
C
Verma
Udit
U
Gaynor
Richard B
RB
Byers
Stephen W
SW
Pestell
Richard G
RG
D001665:Binding Sites; D015153:Blotting, Western; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D019938:Cyclin D1 / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005434:Flow Cytometry; D016193:G1 Phase; D017930:Genes, Reporter; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase; D051821:Lymphoid Enhancer-Binding Factor 1; D008856:Microscopy, Fluorescence; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D016196:S Phase; D015398:Signal Transduction; D013379:Substrate Specificity; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D051176:beta Catenin
D019938:Cyclin D1; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D005982:Glutathione Transferase; D051550:I-kappa B Kinase; D051821:Lymphoid Enhancer-Binding Factor 1; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D015534:Trans-Activators; D014157:Transcription Factors; D051176:beta Catenin; C495270:CTNNB1 protein, human; C496559:CHUK protein, human; C496560:IKBKB protein, human; C496565:IKBKE protein, human