MECHANISMS OF TRANSLATIONAL CONTROL OF APOLIPOPROTEIN B MRNA: IDENTIFICATION OF A NOVEL, INSULIN-SENSITIVE 110 KDA RNA BINDING PROTEIN MEDIATING TRANSLATIONAL STIMULATION OF APOLIPOPROTEIN B MRNA VIA CIS-TRANS INTERACTIONS AT THE 5′ UTR

AbstractSurvival of all living organisms requires the ability to detect attack and swiftly counter with protective immune responses. Despite considerable mechanistic advances, interconnectivity of signaling circuits often remains unclear. A newly-characterized protein, IMMUNOREGULATORY RNA-BINDING PROTEIN (IRR), negatively regulates immune responses in both maize and Arabidopsis, with disrupted function resulting in enhanced disease resistance. IRR physically interacts with, and promotes canonical splicing of, transcripts encoding defense signaling proteins, including the key negative regulator of pattern recognition receptor signaling complexes, CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28). Upon immune activation by Plant Elicitor Peptides (Peps), IRR is dephosphorylated, disrupting interaction withCPK28transcripts and resulting in accumulation of an alternative splice variant encoding a truncated CPK28 protein with impaired kinase activity and diminished function as a negative regulator. We demonstrate a novel circuit linking Pep-induced post-translational modification of IRR with post-transcriptionally-mediated attenuation of CPK28 function to dynamically amplify Pep signaling and immune output.One Sentence SummaryPlant innate immunity is promoted by post-translational modification of a novel RNA-binding protein that regulates alternative splicing of transcripts encoding defense signaling proteins to dynamically increase immune receptor signaling capacity through deactivation of a key signal-buffering circuit.

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The editosome for cytidine to uridine mRNA editing has a native complexity of 27S: identification of intracellular domains containing active and inactive editing factors

Journal of Cell Science ◽

10.1242/jcs.115.5.1027 ◽

2002 ◽

Vol 115 (5) ◽

pp. 1027-1039 ◽

Cited By ~ 5

Author(s):

Mark P. Sowden ◽

Nazzareno Ballatori ◽

Karen L. de Mesy Jensen ◽

Lakesha Hamilton Reed ◽

Harold C. Smith

Keyword(s):

Apolipoprotein B ◽

Rna Binding ◽

Binding Protein ◽

Rna Binding Protein ◽

Catalytic Subunit ◽

Cross Linking ◽

Primary Hepatocytes ◽

Mrna Editing ◽

Apob Mrna ◽

Rat Primary Hepatocytes

Apolipoprotein B mRNA cytidine to uridine editing requires the assembly of a multiprotein editosome comprised minimally of the catalytic subunit,apolipoprotein B mRNA editing catalytic subunit 1 (APOBEC-1), and an RNA-binding protein, APOBEC-1 complementation factor (ACF). A rat homolog has been cloned with 93.5% identity to human ACF (huACF). Peptide-specific antibodies prepared against huACF immunoprecipitated a rat protein of similar mass as huACF bound to apolipoprotein B (apoB) RNA in UV cross-linking reactions, thereby providing evidence that the p66, mooring sequence-selective, RNA-binding protein identified previously in rat liver by UV cross-linking and implicated in editosome assembly is a functional homolog of huACF. The rat protein (p66/ACF) was distributed in both the nucleus and cytoplasm of rat primary hepatocytes. Within a thin section, a significant amount of total cellular p66/ACF was cytoplasmic, with a concentration at the outer surface of the endoplasmic reticulum. Native APOBEC-1 co-fractionated with p66/ACF in the cytoplasm as 60S complexes. In the nucleus, the biological site of apoB mRNA editing, native p66/ACF, was localized to heterochromatin and fractionated with APOBEC-1 as 27S editosomes. When apoB mRNA editing was stimulated in rat primary hepatocytes with ethanol or insulin, the abundance of p66/ACF in the nucleus markedly increased. It is proposed that the heterogeneity in size of complexes containing editing factors is functionally significant and reflects functionally engaged editosomes in the nucleus and an inactive cytoplasmic pool of factors.

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The Nuclear RNA-binding Protein Sam68 Translocates to the Cytoplasm and Associates with the Polysomes in Mouse Spermatocytes

Molecular Biology of the Cell ◽

10.1091/mbc.e05-06-0548 ◽

2006 ◽

Vol 17 (1) ◽

pp. 14-24 ◽

Cited By ~ 60

Author(s):

Maria Paola Paronetto ◽

Francesca Zalfa ◽

Flavia Botti ◽

Raffaele Geremia ◽

Claudia Bagni ◽

...

Keyword(s):

Translational Control ◽

Rna Binding ◽

Rna Binding Proteins ◽

Binding Protein ◽

Rna Binding Protein ◽

Male Meiosis ◽

Binding Motif ◽

Mitogen Activated Protein ◽

Pachytene Spermatocytes ◽

And Function

Translational control plays a crucial role during gametogenesis in organisms as different as worms and mammals. Mouse knockout models have highlighted the essential function of many RNA-binding proteins during spermatogenesis. Herein we have investigated the expression and function during mammalian male meiosis of Sam68, an RNA-binding protein implicated in several aspects of RNA metabolism. Sam68 expression and localization within the cells is stage specific: it is expressed in the nucleus of spermatogonia, it disappears at the onset of meiosis (leptotene/zygotene stages), and it accumulates again in the nucleus of pachytene spermatocytes and round spermatids. During the meiotic divisions, Sam68 translocates to the cytoplasm where it is found associated with the polysomes. Translocation correlates with serine/threonine phosphorylation and it is blocked by inhibitors of the mitogen activated protein kinases ERK1/2 and of the maturation promoting factor cyclinB-cdc2 complex. Both kinases associate with Sam68 in pachytene spermatocytes and phosphorylate the regulatory regions upstream and downstream of the Sam68 RNA-binding motif. Molecular cloning of the mRNAs associated with Sam68 in mouse spermatocytes reveals a subset of genes that might be posttranscriptionally regulated by this RNA-binding protein during spermatogenesis. We also demonstrate that Sam68 shuttles between the nucleus and the cytoplasm in secondary spermatocytes, suggesting that it may promote translation of specific RNA targets during the meiotic divisions.

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Stimulation of Ki-ras Ribozyme Activity by RNA Binding Protein, NCp7, in Vitro and in Pancreatic Tumor Cell Line, Capan 1

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1994.tb17261.x ◽

1994 ◽

Vol 733 (1 Molecular and) ◽

pp. 113-121 ◽

Cited By ~ 3

Author(s):

KARIN MOELLING ◽

GERD MUELLER ◽

JENS DANNULL ◽

CHRISTOPH REUSS ◽

PETER BEIMLING ◽

...

Keyword(s):

Tumor Cell ◽

Cell Line ◽

Pancreatic Tumor ◽

Rna Binding ◽

Binding Protein ◽

Rna Binding Protein ◽

Tumor Cell Line ◽

Pancreatic Tumor Cell ◽

Stimulation Of

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Spnr, a murine RNA-binding protein that is localized to cytoplasmic microtubules.

The Journal of Cell Biology ◽

10.1083/jcb.129.4.1023 ◽

1995 ◽

Vol 129 (4) ◽

pp. 1023-1032 ◽

Cited By ~ 67

Author(s):

J M Schumacher ◽

K Lee ◽

S Edelhoff ◽

R E Braun

Keyword(s):

Translational Control ◽

Rna Binding ◽

Binding Protein ◽

Rna Binding Protein ◽

Translational Repression ◽

Rna Transport ◽

Binding Domains ◽

Cytoplasmic Microtubules ◽

Pachytene Spermatocytes ◽

Expression Libraries

Previous studies in transgenic mice have established the importance of the 3' untranslated region (UTR) of the spermatid-specific protamine-1 (Prm-1) mRNA in its translational control during male germ cell development. To clone genes that mediate the translational repression or activation of the Prm-1 mRNA, we screened cDNA expression libraries made with RNA from pachytene spermatocytes and round spermatids, with an RNA probe corresponding to the 3' UTR of Prm-1. We obtained six independent clones that encode Spnr, a spermatid perinuclear RNA-binding protein. Spnr is a 71-kD protein that contains two previously described RNA binding domains. The Spnr mRNA is expressed at high levels in the testis, ovary, and brain, and is present in multiple forms in those tissues. Immunolocalization of the Spnr protein within the testis shows that it is expressed exclusively in postmeiotic germ cells and that it is localized to the manchette, a spermatid-specific microtubular array. Although the Spnr protein is expressed too late to be directly involved in the translational repression of Prm-1 specifically, we suggest that the Spnr protein may be involved in other aspects of spermatid RNA metabolism, such as RNA transport or translational activation.

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