title: Alternative splicing affects the subcellular localization of Drosha.
abstract: The RNase III enzyme Drosha is a key factor in microRNA (miRNA) biogenesis and as such indispensable for cellular homeostasis and developmental processes. Together with its co-factor DGCR8, it converts the primary transcript (pri-miRNA) into the precursor hairpin (pre-miRNA) in the nucleus. While the middle and the C-terminal domain are crucial for pri-miRNA processing and DGCR8 binding, the function of the N-terminus remains cryptic. Different studies have linked this region to the subcellular localization of Drosha, stabilization and response to stress. In this study, we identify alternatively spliced Drosha transcripts that are devoid of a part of the arginine/serine-rich (RS-rich) domain and expressed in a large set of human cells. In contrast to their expected habitation, we find two isoforms also present in the cytoplasm, while the other two isoforms reside exclusively in the nucleus. Their processing activity for pri-miRNAs and the binding to co-factors remains unaltered. In multiple cell lines, the endogenous mRNA expression of the Drosha isoforms correlates with the localization of endogenous Drosha proteins. The pri-miRNA processing efficiency is not significantly different between groups of cells with or without cytoplasmic Drosha expression. In summary, we discovered novel isoforms of Drosha with differential subcellular localization pointing toward additional layers of complexity in the regulation of its activity.
authors.affiliation: Division of RNA Biology and Cancer (B150), German Cancer Research Center (DKFZ), Heidelberg, Germany Institute of Pathology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Link
authors.affiliation: Division of RNA Biology and Cancer (B150), German Cancer Research Center (DKFZ), Heidelberg, Germany Institute of Pathology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Stefanie E
authors.initials: SE
authors.lastname: Grund
authors.affiliation: Division of Cancer Research, Dept. of Thoracic Surgery, Medical Center-University of Freiburg, Freiburg, Germany Faculty of Medicine, University of Freiburg, Freiburg, Germany Division of RNA Biology and Cancer (B150), German Cancer Research Center (DKFZ), Heidelberg, Germany German Cancer Consortium (DKTK), Freiburg, Germany Institute of Pathology, University of Heidelberg, Heidelberg, Germany Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany s.diederichs@dkfz.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Diederichs
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D019913:Nuclear Localization Signals; D009928:Organ Specificity; D011485:Protein Binding; D021381:Protein Transport; D034622:RNA Interference; D034443:RNA Transport; D016601:RNA-Binding Proteins / Q000378:metabolism; D043244:Ribonuclease III / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D035683:MicroRNAs; D019913:Nuclear Localization Signals; D016601:RNA-Binding Proteins; D043244:Ribonuclease III