BLCAP

Abstract: A-to-I RNA editing by ADARs is a post-transcriptional mechanism for expanding the proteomic repertoire. Genetic recoding by editing was so far observed for only a few mammalian RNAs that are predominantly expressed in nervous tissues. However, as these editing targets fail to explain the broad and severe phenotypes of ADAR1 knockout mice, additional targets for editing by ADARs were always expected. Using comparative genomics and expressed sequence analysis, we identified and experimentally verified four additional candidate human substrates for ADAR-mediated editing: FLNA, BLCAP, CYFIP2 and IGFBP7. Additionally, editing of three of these substrates was verified in the mouse while two of them were validated in chicken. Interestingly, none of these substrates encodes a receptor protein but two of them are strongly expressed in the CNS and seem important for proper nervous system function. The editing pattern observed suggests that some of the affected proteins might have altered physiological properties leaving the possibility that they can be related to the phenotypes of ADAR1 knockout mice.

Abstract: To better understand the molecular basis of radiation-induced osteosarcoma (OS), we performed global gene expression profiling of rat OS tumors induced by the bone-seeking alpha emitter (238)Pu, and the expression profiles were compared with those of normal osteoblasts (OB). The expressions of 72 genes were significantly differentially expressed in the tumors related to OB. These included genes involved in the cell adhesion (e.g., Podxl, Col18a1, Cd93, Emcn and Vcl), differentiation, developmental processes (e.g., Hhex, Gata2, P2ry6, P2rx5, Cited2, Osmr and Igsf10), tumor-suppressor function (e.g., Nme3, Blcap and Rrm1), Src tyrosine kinase signaling (e.g., Hck, Shf, Arhgap29, Cttn and Akap12), and Wnt/beta-catenin signaling (e.g., Fzd6, Lzic, Dkk3 and Ctnna1) pathways. Expression changes of several genes were validated by quantitative real-time RT-PCR analysis. Notably, all of the identified genes involved in the Wnt/beta-catenin signaling pathway were known or proposed to be negative regulators of this pathway and were downregulated in the tumors, suggesting the activation of beta-catenin in radiation-induced OS. By using immunohistochemical and immunoblot analyses, constitutive activation of the Wnt/beta-catenin signaling pathway in the tumors was confirmed by observing nuclear and/or cytoplasmic localization of beta-catenin and a decrease in its inactive (phosphorylated) form. Furthermore, we found a significant reduction in the levels of glycogen synthase kinase 3beta (GSK-3beta) protein in the tumors relative to OB. Taken together, these findings provide new insights into the molecular basis of radiation-induced OS.