scholarly journals The RNA-editing Enzyme ADAR1 Is Localized to the Nascent Ribonucleoprotein Matrix on Xenopus Lampbrush Chromosomes but Specifically Associates with an Atypical Loop

1999 ◽  
Vol 144 (4) ◽  
pp. 603-615 ◽  
Author(s):  
Christian R. Eckmann ◽  
Michael F. Jantsch
Keyword(s):  
Rna Editing ◽  
Chromosomal Localization ◽  
Mutational Analysis ◽  
Independent Manner ◽  
Double Stranded Rna ◽  
Entire Chromosome ◽  
A Site ◽  
Substrate Independent ◽  
Editing Enzyme ◽  
Transcriptionally Active Chromosome

Double-stranded RNA adenosine deaminase (ADAR1, dsRAD, DRADA) converts adenosines to inosines in double-stranded RNAs. Few candidate substrates for ADAR1 editing are known at this point and it is not known how substrate recognition is achieved. In some cases editing sites are defined by basepaired regions formed between intronic and exonic sequences, suggesting that the enzyme might function cotranscriptionally. We have isolated two variants of Xenopus laevis ADAR1 for which no editing substrates are currently known. We demonstrate that both variants of the enzyme are associated with transcriptionally active chromosome loops suggesting that the enzyme acts cotranscriptionally. The widespread distribution of the protein along the entire chromosome indicates that ADAR1 associates with the RNP matrix in a substrate-independent manner. Inhibition of splicing, another cotranscriptional process, does not affect the chromosomal localization of ADAR1. Furthermore, we can show that the enzyme is dramatically enriched on a special RNA-containing loop that seems transcriptionally silent. Detailed analysis of this loop suggests that it might represent a site of ADAR1 storage or a site where active RNA editing is taking place. Finally, mutational analysis of ADAR1 demonstrates that a putative Z-DNA binding domain present in ADAR1 is not required for chromosomal targeting of the protein.

scholarly journals Mutational analysis of apolipoprotein B mRNA editing enzyme (APOBEC1): structure–function relationships of RNA editing and dimerization

1999 ◽  
Vol 40 (4) ◽  
pp. 623-635 ◽  
Author(s):  
Ba-Bie Teng ◽  
Scott Ochsner ◽  
Qian Zhang ◽  
Kizhake V. Soman ◽  
Paul P. Lau ◽  
...  
Keyword(s):  
Structure Function ◽  
Rna Editing ◽  
Apolipoprotein B ◽  
Mutational Analysis ◽  
Mrna Editing ◽  
Editing Enzyme

scholarly journals Distinct in vivo roles for double-stranded RNA-binding domains of the Xenopus RNA-editing enzyme ADAR1 in chromosomal targeting

2003 ◽  
Vol 161 (2) ◽  
pp. 309-319 ◽  
Author(s):  
Michael Doyle ◽  
Michael F. Jantsch
Keyword(s):  
Rna Editing ◽  
Rna Binding ◽  
Double Stranded Rna ◽  
Binding Domains ◽  
Initial Substrate ◽  
Rna Binding Domains ◽  
Editing Enzyme ◽  
Deaminase Domain

The RNA-editing enzyme adenosine deaminase that acts on RNA (ADAR1) deaminates adenosines to inosines in double-stranded RNA substrates. Currently, it is not clear how the enzyme targets and discriminates different substrates in vivo. However, it has been shown that the deaminase domain plays an important role in distinguishing various adenosines within a given substrate RNA in vitro. Previously, we could show that Xenopus ADAR1 is associated with nascent transcripts on transcriptionally active lampbrush chromosomes, indicating that initial substrate binding and possibly editing itself occurs cotranscriptionally. Here, we demonstrate that chromosomal association depends solely on the three double-stranded RNA-binding domains (dsRBDs) found in the central part of ADAR1, but not on the Z-DNA–binding domain in the NH2 terminus nor the catalytic deaminase domain in the COOH terminus of the protein. Most importantly, we show that individual dsRBDs are capable of recognizing different chromosomal sites in an apparently specific manner. Thus, our results not only prove the requirement of dsRBDs for chromosomal targeting, but also show that individual dsRBDs have distinct in vivo localization capabilities that may be important for initial substrate recognition and subsequent editing specificity.

scholarly journals An extra double-stranded RNA binding domain confers high activity to a squid RNA editing enzyme

RNA ◽  
2009 ◽  
Vol 15 (6) ◽  
pp. 1208-1218 ◽  
Author(s):  
J. P. Palavicini ◽  
M. A. O'connell ◽  
J. J.C. Rosenthal
Keyword(s):  
High Activity ◽  
Rna Editing ◽  
Rna Binding ◽  
Binding Domain ◽  
Double Stranded Rna ◽  
Rna Binding Domain ◽  
Editing Enzyme

scholarly journals Chromosomal Storage of the RNA-editing Enzyme ADAR1 in Xenopus Oocytes

2005 ◽  
Vol 16 (7) ◽  
pp. 3377-3386 ◽  
Author(s):  
Nina B. Sallacz ◽  
Michael F. Jantsch
Keyword(s):  
Rna Editing ◽  
Binding Sites ◽  
Rna Binding ◽  
Adenosine Deaminases ◽  
A Site ◽  
Nascent Transcripts ◽  
Editing Enzyme ◽  
Nuclear Injection ◽  
Processing Factors

ADARs (adenosine deaminases that act on RNA) are RNA-editing enzymes that convert adenosines to inosines in structured or double-stranded RNAs. Expression and intracellular distribution of ADAR1 is controlled by a plethora of mechanisms suggesting that enzyme activity has to be tightly regulated. Mammalian ADAR1 is a shuttling protein, whereas Xenopus ADAR1 is exclusively nuclear. In oocytes, Xenopus ADAR1 associates with most nascent transcripts but is strongly enriched at a specific site on chromosome 3, termed the special loop. Enrichment at this site requires the presence of RNAs but is independent of ongoing transcription. Here we show that RNAs transcribed elsewhere in the genome accumulate at the special loop even in the absence of transcription. In situ hybridization experiments, however, indicate the absence of known editing substrates from this site. In the absence of transcription also other RNA binding and processing factors accumulate at the special loop, suggesting that ADAR1 is stored or assembled at the special loop in an RNA-containing complex. Nuclear injection of RNAs providing binding sites for ADAR1 dissociates the enzyme from the special loop, supporting the notion that the special loop represents a site where ADAR1 is stored, possibly for later use during development.

scholarly journals Extra Double-stranded RNA Binding Domain (dsRBD) in a Squid RNA Editing Enzyme Confers Resistance to High Salt Environment

2012 ◽  
Vol 287 (21) ◽  
pp. 17754-17764 ◽  
Author(s):  
Juan Pablo Palavicini ◽  
Rodrigo A. Correa-Rojas ◽  
Joshua J. C. Rosenthal
Keyword(s):  
Rna Editing ◽  
Rna Binding ◽  
Binding Domain ◽  
High Salt ◽  
Double Stranded Rna ◽  
Rna Binding Domain ◽  
Editing Enzyme

scholarly journals Nucleocytoplasmic Distribution of Human RNA-editing Enzyme ADAR1 Is Modulated by Double-stranded RNA-binding Domains, a Leucine-rich Export Signal, and a Putative Dimerization Domain

2002 ◽  
Vol 13 (11) ◽  
pp. 3822-3835 ◽  
Author(s):  
Alexander Strehblow ◽  
Martina Hallegger ◽  
Michael F. Jantsch
Keyword(s):  
Rna Editing ◽  
Nuclear Localization ◽  
Nuclear Export ◽  
Rna Binding ◽  
Nuclear Export Signal ◽  
Nuclear Accumulation ◽  
Double Stranded Rna ◽  
Cytoplasmic Accumulation ◽  
Editing Enzyme ◽  
Export Signal

The human RNA-editing enzyme adenosine deaminase that acts on RNA (ADAR1) is expressed in two versions. A longer 150-kDa protein is interferon inducible and can be found both in the nucleus and cytoplasm. An amino-terminally truncated 110-kDa version, in contrast, is constitutively expressed and predominantly nuclear. In the absence of transcription, however, the shorter protein is also cytoplasmic and thus displays the hallmarks of a shuttling protein. The nuclear localization signal (NLS) of human hsADAR1 is atypical and overlaps with its third double-stranded RNA-binding domain (dsRBD). Herein, we identify regions in hsADAR1 that interfere with nuclear localization and mediate cytoplasmic accumulation. We show that interferon-inducible hsADAR1 contains a Crm1-dependent nuclear export signal in its amino terminus. Most importantly, we demonstrate that the first dsRBD of hsADAR1 interferes with nuclear localization of a reporter construct containing dsRBD3 as an active NLS. The same effect can be triggered by several other, but not all dsRBDs. Active RNA binding of either the inhibitory dsRBD1 or the NLS bearing dsRBD3 is required for cytoplasmic accumulation. Furthermore, hsADAR1's dsRBD1 has no effect on other NLSs, suggesting RNA-mediated cross talk between dsRBDs, possibly leading to masking of the NLS. A model, incorporating these findings is presented. Finally, we identify a third region located in the C terminus of hsADAR1 that also interferes with nuclear accumulation of this protein.

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