ABSTRACT
Long non-coding RNAs (lncRNAs) are frequently dysregulated in a variety of human cancers. However, their biological roles in these cancers remain incompletely understood. In this study, we analyze the gene expression profiles of colon cancer tissues and identify a previously unannotated lncRNA, FLJ39051, that we term GSEC (G-quadruplex-forming sequence containing lncRNA), as a lncRNA that is upregulated in colorectal cancer. We further demonstrate that knockdown of GSEC results in the reduction of colon cancer cell motility. We also show that GSEC binds to the DEAH box polypeptide 36 (DHX36) RNA helicase via its G-quadruplex-forming sequence and inhibits DHX36 G-quadruplex unwinding activity. Moreover, knockdown of DHX36 restores the reduced migratory activity of colon cancer cells caused by GSEC knockdown. These results suggest that GSEC plays an important role in colon cancer cell migration by inhibiting the function of DHX36 via its G-quadruplex structure.
Subject(s)
Cell Movement , Colonic Neoplasms/pathology , DEAD-box RNA Helicases/antagonists & inhibitors , G-Quadruplexes , RNA, Long Noncoding/genetics , RNA, Neoplasm/metabolism , Apoptosis , Binding Sites , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , Cell Proliferation , Colonic Neoplasms/genetics , Colonic Neoplasms/metabolism , DEAD-box RNA Helicases/genetics , DEAD-box RNA Helicases/metabolism , Humans , Neoplasm Staging , Prognosis , Protein Binding , RNA, Long Noncoding/metabolism , RNA, Neoplasm/genetics , Tumor Cells, CulturedABSTRACT
Growth and patterning of the Drosophila wing is controlled in part by the long-range organizing activities of the Decapentaplegic protein (Dpp). Dpp is synthesized by cells that line the anterior side of the anterior/posterior compartment border of the wing imaginal disc. From this source, Dpp is thought to generate a concentration gradient that patterns both anterior and posterior compartments. Among the gene targets that it regulates are optomotor blind (omb), spalt (sal), and daughters against dpp (dad). We report here the molecular cloning of brinker (brk), and show that brk expression is repressed by dpp. brk encodes, a protein that negatively regulates Dpp-dependent genes. Expression of brk in Xenopus embryos indicates that brk can also repress the targets of a vertebrate homologue of Dpp, bone morphogenetic protein 4 (BMP-4). The evolutionary conservation of Brk function underscores the importance of its negative role in proportioning Dpp activity.
Subject(s)
Drosophila Proteins , Gene Expression Regulation , Insect Proteins/genetics , Insect Proteins/physiology , Repressor Proteins , Transcription Factors , Amino Acid Sequence , Animals , Bone Morphogenetic Protein 4 , Bone Morphogenetic Proteins/antagonists & inhibitors , Bone Morphogenetic Proteins/metabolism , Cloning, Molecular , Drosophila , Genes, Insect , Molecular Sequence Data , Mutation , Recombinant Fusion Proteins/genetics , Signal Transduction , Transforming Growth Factor beta , Wings, Animal/embryology , Xenopus , Xenopus ProteinsABSTRACT
The family of TGF-beta signalling molecules play inductive roles in various developmental contexts. One member of this family, Drosophila Decapentaplegic (Dpp) serves as a morphogen that patterns both the embryo and adult. We have now isolated a gene, Daughters against dpp (Dad), whose transcription is induced by Dpp. Dad shares weak homology with Drosophila Mad (Mothers against dpp), a protein required for transduction of Dpp signals. In contrast to Mad or the activated Dpp receptor, whose overexpression hyperactivates the Dpp signalling pathway, overexpression of Dad blocks Dpp activity. Expression of Dad together with either Mad or the activated receptor rescues phenotypic defects induced by each protein alone. Dad can also antagonize the activity of a vertebrate homologue of Dpp, bone morphogenetic protein, as evidenced by induction of dorsal or neural fate following overexpression in Xenopus embryos. We conclude that the pattern-organizing mechanism governed by Dpp involves a negative-feedback circuit in which Dpp induces expression of its own antagonist, Dad. This feedback loop appears to be conserved in vertebrate development.