Mutations in MAP3K1 that cause 46,XY disorders of sex development disrupt distinct structural domains in the protein
HUMAN MOLECULAR GENETICS
Authors: Chamberlin, Adam; Huether, Robert; Machado, Aline Z.; Groden, Michael; Liu, Hsiao-Mei; Upadhyay, Kinnari; Vivian, O.; Gomes, Nathalia L.; Lerario, Antonio M.; Nishi, Mirian Y.; Costa, Elaine M. F.; Mendonca, Berenice; Domenice, Sorahia; Velasco, Jacqueline; Loke, Johnny; Ostrer, Harry
Abstract
Missense mutations in the gene, MAP3K1, are a common cause of 46,XY gonadal dysgenesis, accounting for 15-20% of cases [Ostrer, 2014, Disorders of sex development (DSDs): an update. J. Clin. Endocrinol. Metab., 99, 1503-1509]. Functional studies demonstrated that all of these mutations cause a protein gain-of-function that alters co-factor binding and increases phosphorylation of the downstream MAP kinase pathway targets, MAPK11, MAP3K and MAPK1. This dysregulation of the MAP kinase pathway results in increased CTNNB1, increased expression of WNT4 and FOXL2 and decreased expression of SRY and SOX9. Unique and recurrent pathogenic mutations cluster in three semi-contiguous domains outside the kinase region of the protein, a newly identified N-terminal domain that shares homology with the Guanine Exchange Factor (residues Met164 to Glu231), a Plant HomeoDomain (residues Met442 to Trp495) and an ARMadillo repeat domain (residues Met566 to Glu862). Despite the presence of the mutation clusters and clinical data, there exists a dearth of mechanistic insights behind the development imbalance. In this paper, we use structural modeling and functional data of these mutations to understand alterations of the MAP3K1 protein and the effects on protein folding, binding and downstream target phosphorylation. We show that these mutations have differential effects on protein binding depending on the domains in which they occur. These mutations increase the binding of the RHOA, MAP3K4 and FRAT1 proteins and generally decrease the binding of RAC1. Thus, pathologies in MAP3K1 disrupt the balance between the pro-kinase activities of the RHOA and MAP3K4 binding partners and the inhibitory activity of RAC1.
Circular RNA Pleiotrophin promotes carcinogenesis in glioma via regulation of microRNA-122/SRY-box transcription factor 6 axis
EUROPEAN JOURNAL OF CANCER PREVENTION
Authors: Chen, Chen; Deng, Lu; Nie, De-Kang; Jia, Feng; Fu, Lin-Shan; Wan, Zheng-Qiang; Lan, Qing
Abstract
Background: Circular RNAs (circRNAs) are recently identified as gene regulators in mammals and play important roles in carcinogenesis of cancer. For example, circRNA_PTN has been recognized as a biomarker of human cancer and is overexpressed in glioma. The molecular function of circRNA_PTN and its downstream targets in glioma, however, remains elusive. Methods: Quantitative polymerase chain reaction analysis was used to measure the expression of circular RNA pleiotrophin (circ_PTN) and miR-122. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, propidium iodide and Annexin-V/propidium iodide assay were performed to determine cell proliferation and apoptosis of glioma cells. Circular RNA Interactome and TargetScan were used to predict the potential microRNA targeting of circ_PTN and the potential targets of miR-122, respectively. Luciferase activity assay was used to validate these interactions. Downstream molecular mechanisms, including SRY-box transcription factor 6 (SOX6), extracellular regulated protein kinases (ERK), Cyclin D1, B-cell lymphoma-2 (BCL-2) and BCL2 associated X, apoptosis regulator (BAX), were determined by western blot. Results: Circ_PTN was overexpressed in glioma cells, and its knockdown induced cell proliferation inhibition, cell cycle arrest and apoptosis in glioma cells. The target microRNA of circ_PTN was predicted to be miR-122, the expression of which was negatively correlated with circ_PTN in glioma cells. Moreover, SOX6 was predicted as a potential target of miR-122, and miR-122 overexpression decreased SOX6 expression. MiR-122 inhibitor reversed the tumor-suppressing effects of circ_PTN knockdown, while overexpression of SOX6 impaired the miR-122 overexpression-induced cell growth inhibition and apoptosis. In addition, mitogen activated kinase-like protein (MAPK)/ERK pathway was involved in circ_PTN/miR-122/SOX6 axis. Conclusions: Circ_PTN acted as a sponge of miR-122 and upregulated miR-122 target SOX6, thus promoting carcinogenesis of glioma cells.