Spatially regulated editing of genetic information within a neuron.

Eli Eisenberg,Isabel C Vallecillo-Viejo,Joshua J C Rosenthal,Juan F Diaz Quiroz,Kavita J Rangan,Maria F Montiel-Gonzalez,Noa Liscovitch-Brauer,Simon R Levinson,Sonya E Nemes

doi:10.1093/nar/gkaa172

Eli Eisenberg, Isabel C Vallecillo-Viejo + Show 7 more

Open Access

https://doi.org/10.1093/nar/gkaa172

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Abstract

In eukaryotic cells, with the exception of the specialized genomes of mitochondria and plastids, all genetic information is sequestered within the nucleus. This arrangement imposes constraints on how the information can be tailored for different cellular regions, particularly in cells with complex morphologies like neurons. Although messenger RNAs (mRNAs), and the proteins that they encode, can be differentially sorted between cellular regions, the information itself does not change. RNA editing by adenosine deamination can alter the genome’s blueprint by recoding mRNAs; however, this process too is thought to be restricted to the nucleus. In this work, we show that ADAR2 (adenosine deaminase that acts on RNA), an RNA editing enzyme, is expressed outside of the nucleus in squid neurons. Furthermore, purified axoplasm exhibits adenosine-to-inosine activity and can specifically edit adenosines in a known substrate. Finally, a transcriptome-wide analysis of RNA editing reveals that tens of thousands of editing sites (>70% of all sites) are edited more extensively in the squid giant axon than in its cell bodies. These results indicate that within a neuron RNA editing can recode genetic information in a region-specific manner.

Highlights

Genetic information passes faithfully from DNA to RNA before being translated into proteins; there are exceptions
As an initial test of the antisera’s specificity, FLAG epitope-tagged clones of SqADAR2a, SqADAR2b and rat ADAR2 (rADAR2) were transiently transfected into HEK-293T cells and total protein extracts were processed for western blots (Figure 1B)
Data from this paper suggest that region-specific RNA editing occurs in squid axons

Summary

Introduction

Genetic information passes faithfully from DNA to RNA before being translated into proteins; there are exceptions. A variety of biochemical processes, collectively known as RNA editing, can alter it as it passes through RNA. The most common form of RNA editing in multicellular animals involves the hydrolytic deamination of adenosine to inosine (A→I), a nucleotide that is a biological mimic for guanosine [1]. This process is catalyzed by the ADAR (adenosine deaminase that acts on RNA) family of enzymes and individual editing events regulate the functional properties of a wide variety of proteins, including ligand- and voltage-gated ion channels, neurotransmitter receptors and other messages that are vital for nervous system function [2]. Evidence supporting the dogma that all recoding is nuclear is generally indirect and based on relatively few examples; only in humans, mice and flies has the overall extent of editing been determined cotranscriptionally [3,4,5]

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