Requirements for iron-regulated degradation of the RNA binding protein, iron regulatory protein 2.

Abstract Type III interferons (IFNs) are the latest members of the IFN family. They play an important role in immune defense mechanisms, especially in antiviral responses at mucosal sites. Moreover, they control inflammatory reactions by modulating neutrophil and dendritic cell functions. Therefore, it is important to identify cellular mechanisms involved in the control of type III IFN expression. All IFN family members contain AU-rich elements (AREs) in the 3′-untranslated regions (3′-UTR) of their mRNAs that determine mRNA half-life and consequently the expressional level of these cytokines. mRNA stability is controlled by different proteins binding to these AREs leading to either stabilization or destabilization of the respective target mRNA. The KH-type splicing regulatory protein KSRP (also named KHSRP) is an important negative regulator of ARE-containing mRNAs. Here, we identify the interferon lambda 3 (IFNL3) mRNA as a new KSRP target by pull-down and immunoprecipitation experiments, as well as luciferase reporter gene assays. We characterize the KSRP-binding site in the IFNL3 3′-UTR and demonstrate that KSRP regulates the mRNA half-life of the IFNL3 transcript. In addition, we detect enhanced expression of IFNL3 mRNA in KSRP−/− mice, establishing a negative regulatory function of KSRP in type III IFN expression also in vivo. Besides KSRP the RNA-binding protein AUF1 (AU-rich element RNA-binding protein 1) also seems to be involved in the regulation of type III IFN mRNA expression.

Download Full-text

The RNA-binding protein Hfq assembles into foci-like structures in nitrogen starved Escherichia coli

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014107 ◽

2020 ◽

Vol 295 (35) ◽

pp. 12355-12367

Author(s):

Josh McQuail ◽

Amy Switzer ◽

Lynn Burchell ◽

Sivaramesh Wigneshweraraj

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Adaptive Response ◽

Rna Binding ◽

Nitrogen Starvation ◽

Binding Protein ◽

Regulatory Protein ◽

Rna Binding Protein ◽

E Coli

The initial adaptive responses to nutrient depletion in bacteria often occur at the level of gene expression. Hfq is an RNA-binding protein present in diverse bacterial lineages that contributes to many different aspects of RNA metabolism during gene expression. Using photoactivated localization microscopy and single-molecule tracking, we demonstrate that Hfq forms a distinct and reversible focus-like structure in Escherichia coli specifically experiencing long-term nitrogen starvation. Using the ability of T7 phage to replicate in nitrogen-starved bacteria as a biological probe of E. coli cell function during nitrogen starvation, we demonstrate that Hfq foci have a role in the adaptive response of E. coli to long-term nitrogen starvation. We further show that Hfq foci formation does not depend on gene expression once nitrogen starvation has set in and occurs indepen-dently of the transcription factor N-regulatory protein C, which activates the initial adaptive response to N starvation in E. coli. These results serve as a paradigm to demonstrate that bacterial adaptation to long-term nutrient starvation can be spatiotemporally coordinated and can occur independently of de novo gene expression during starvation.

Download Full-text

Identification of an RNA-binding protein that is phosphorylated by PTH and potentially mediates PTH-induced destabilization of Npt2a mRNA

AJP Cell Physiology ◽

10.1152/ajpcell.00192.2015 ◽

2016 ◽

Vol 310 (3) ◽

pp. C205-C215 ◽

Cited By ~ 6

Author(s):

Rebecca D. Murray ◽

Michael L. Merchant ◽

Ericka Hardin ◽

Barbara Clark ◽

Syed J. Khundmiri ◽

...

Keyword(s):

Rna Binding ◽

Binding Protein ◽

Regulatory Protein ◽

Rna Binding Protein ◽

Rna Isolation ◽

Pcr Analysis ◽

Proximal Tubule Cell ◽

Opossum Kidney ◽

Ok Cells ◽

Sodium Hydrogen Exchanger

Parathyroid hormone (PTH) is a key regulator of the expression and function of the type IIa sodium-phosphate cotransporter (Npt2a), the protein responsible for regulated renal phosphate reabsorption. We previously showed that PTH induces rapid decay of Npt2a mRNA through posttranscriptional mechanisms. We hypothesized that PTH-induced changes in RNA-binding protein (RBP) activity mediate the degradation of Npt2a mRNA. To address this aim, we treated opossum kidney (OK) cells, a PTH-sensitive proximal tubule cell culture model, with 100 nM PTH for 30 min and 2 h, followed by mass spectrometry characterization of the PTH-stimulated phosphoproteome. We identified 1,182 proteins differentially phosphorylated in response to PTH, including 68 RBPs. Preliminary analysis identified a phospho-RBP, hnRNPK-homology-type-splicing regulatory protein (KSRP), with predicted binding sites for the 3′-untranslated region (UTR) of Npt2a mRNA. Western blot analysis confirmed expression of KSRP in OK cells and showed PTH-dependent translocation to the nucleus. Immunoprecipitation of KSRP from control and PTH-treated cells followed by RNA isolation and RT-quantitative PCR analysis identified Npt2a mRNA from both control and PTH-treated KSRP pulldowns. Knockdown of KSRP followed by PTH treatment showed that KSRP is required for mediating PTH-stimulated reduction in sodium/hydrogen exchanger 3 mRNA, but not Npt2a mRNA. We conclude that 1) PTH is a major regulator of both transcription and translation, and 2) KSRP binds Npt2a mRNA but its role in PTH regulation of Npt2a mRNA is not clear.

Download Full-text

The RNA-Binding Protein ESRP1 Modulates the Expression of RAC1b in Colorectal Cancer Cells

Cancers ◽

10.3390/cancers13164092 ◽

2021 ◽

Vol 13 (16) ◽

pp. 4092

Author(s):

Marta Manco ◽

Ugo Ala ◽

Daniela Cantarella ◽

Emanuela Tolosano ◽

Enzo Medico ◽

...

Keyword(s):

Colorectal Cancer ◽

Cancer Cells ◽

Rna Binding ◽

Rna Binding Proteins ◽

Binding Protein ◽

Regulatory Protein ◽

Rna Binding Protein ◽

Mrna Translation ◽

Dependent Manner ◽

Colorectal Cancer Cells

RNA binding proteins are well recognized as critical regulators of tumorigenic processes through their capacity to modulate RNA biogenesis, including alternative splicing, RNA stability and mRNA translation. The RNA binding protein Epithelial Splicing Regulatory Protein 1 (ESRP1) can act as a tumor suppressor or promoter in a cell type- and disease context-dependent manner. We have previously shown that elevated expression of ESRP1 in colorectal cancer cells can drive tumor progression. To gain further insights into the pro-tumorigenic mechanism of action of ESRP1, we performed cDNA microarray analysis on two colorectal cells lines modulated for ESRP1 expression. Intriguingly, RAC1b was highly expressed, both at mRNA and protein levels, in ESRP1-overexpressing cells, while the opposite trend was observed in ESRP1-silenced CRC cells. Moreover, RAC1 and RAC1b mRNA co-immunoprecipitate with ESRP1 protein. Silencing of RAC1b expression significantly reduced the number of soft agar colonies formed by ESRP1-overexpressing cells, suggesting that ESRP1 acted, at least partially, through RAC1b in its tumor-promoting activities in CRC cells. Thus, our data provide molecular cues on targetable candidates in CRC cases with high ESRP1 expression.

Download Full-text