title: The cyclin-dependent kinase inhibitor p16INK4a physically interacts with transcription factor Sp1 and cyclin-dependent kinase 4 to transactivate microRNA-141 and microRNA-146b-5p spontaneously and in response to ultraviolet light-induced DNA damage.
abstract: p16(INK4a) is a tumor suppressor protein involved in several stress-related cellular responses, including apoptosis. Recent lines of evidence indicate that p16(INK4a) is also a modulator of gene expression. However, the molecular mechanisms underlying this novel function are still obscure. Here, we present clear evidence that p16(INK4a) modulates the levels of various microRNAs, with marked positive effect on miR-141 and miR-146b-5p. This effect is mediated through the formation of the p16-CDK4-Sp1 heterocomplex, which binds to Sp1 consensus-binding motifs present in the promoters of miR-141 and miR-146b-5p, and it enables their transcription. In addition, we have shown that p16(INK4a) interacts with Sp1 through the fourth ankyrin repeat, which is crucial for Sp1 binding to the miR-141 and miR-146b-5p promoters and their transcriptional activation. The physiological importance of this association was revealed by the inability of cancer-related p16(INK4a) mutants to interact with Sp1. Moreover, we have shown p16-CDK4-Sp1-dependent up-regulation of miR-141 and miR-146b-5p following UV light-induced DNA damage and the role of these two microRNAs in mediating p16-related induction of apoptosis in response to this genotoxic stress. Together, these results indicate that p16(INK4a) associates with CDK4 not only to inhibit the cell cycle but also to enable the transcription of two important onco-microRNAs, which act as downstream effectors.
authors.affiliation: From the Department of Molecular Oncology, King Faisal Specialist Hospital and Research Centre, MBC 03, P. O. Box 3354, Riyadh 11211, Kingdom of Saudi Arabia.
authors.forename: Huda H
authors.initials: HH
authors.lastname: Al-Khalaf
authors.forename: Peer
authors.initials: P
authors.lastname: Mohideen
authors.forename: Shreeram C
authors.initials: SC
authors.lastname: Nallar
authors.forename: Dhananjaya V
authors.initials: DV
authors.lastname: Kalvakolanu
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Aboussekhra
mesh_terms: D001483:Base Sequence; D002453:Cell Cycle; D002460:Cell Line; D051358:Cyclin-Dependent Kinase 4 / Q000737:chemistry / Q000378:metabolism*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000737:chemistry / Q000378:metabolism*; D004249:DNA Damage; D006801:Humans; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020871:RNA Stability; D016329:Sp1 Transcription Factor / Q000737:chemistry / Q000378:metabolism*; D015533:Transcriptional Activation / Q000528:radiation effects; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; C533895:MIRN141 microRNA, human; C542542:MIRN146 microRNA, human; D035683:MicroRNAs; D046912:Multiprotein Complexes; D016329:Sp1 Transcription Factor; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4
keywords: Protein Complexes; Protein-DNA Interaction; Signaling; Tumor suppressor gene; shRNA