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PprA Contributes to Deinococcus radiodurans Resistance to Nalidixic Acid, Genome Maintenance after DNA Damage and Interacts with Deinococcal Topoisomerases  [PDF]
Swathi Kota, Vijaya K. Charaka, Simon Ringgaard, Matthew K. Waldor, Hari S. Misra
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085288
Abstract: PprA is known to contribute to Deinococcus radiodurans' remarkable capacity to survive a variety of genotoxic assaults. The molecular bases for PprA's role(s) in the maintenance of the damaged D. radiodurans genome are incompletely understood, but PprA is thought to promote D. radiodurans's capacity for DSB repair. PprA is found in a multiprotein DNA processing complex along with an ATP type DNA ligase, and the D. radiodurans toposiomerase IB (DraTopoIB) as well as other proteins. Here, we show that PprA is a key contributor to D. radiodurans resistance to nalidixic acid (Nal), an inhibitor of topoisomerase II. Growth of wild type D. radiodurans and a pprA mutant were similar in the absence of exogenous genotoxic insults; however, the pprA mutant exhibited marked growth delay and a higher frequency of anucleate cells following treatment with DNA-damaging agents. We show that PprA interacts with both DraTopoIB and the Gyrase A subunit (DraGyrA) in vivo and that purified PprA enhances DraTopoIB catalysed relaxation of supercoiled DNA. Thus, besides promoting DNA repair, our findings suggest that PprA also contributes to preserving the integrity of the D. radiodurans genome following DNA damage by interacting with DNA topoisomerases and by facilitating the actions of DraTopoIB.
AUF1 is involved in splenic follicular B cell maintenance
Navid Sadri, Jin-Yu Lu, Michelle L Badura, Robert J Schneider
BMC Immunology , 2010, DOI: 10.1186/1471-2172-11-1
Abstract: Mice lacking AUF1 exhibit an altered proportion and size of splenic B cell subsets. We show prominent apoptosis in splenic B cell follicles and reduced expression of Bcl-2, A1, and Bcl-XL correlate with increased turnover and significant reduction in the number and proportion of splenic FO B cells in AUF1-deficient mice. In addition, AUF1-deficient mice exhibit a sharp decrease in splenic size and lymphocyte cellularity. Bone marrow transfer studies demonstrate that AUF1 deficiency induces cell-autonomous defects in mature B cell subsets but not in the overall number of splenocytes. Reconstitution of irradiated adult AUF1-deficient mice with wild-type bone marrow restores the proportion of FO and marginal zone (MZ) B cells, but does not rescue the decrease in the number of splenocytes. Functionally, AUF1-deficient mice mount an attenuated response to T cell-independent (TI) antigen, which correlates with impaired MZ B cell function.These data indicate that AUF1 is important in the maintenance of splenic FO B cells and adequate humoral immune responses.The mammalian spleen functions to remove old and damaged erythrocytes, participates in the immune response, particularly against blood-borne pathogens, and is the major site for peripheral B cell development [1]. Immature surface immunoglobulin-expressing B cells that reach the spleen from the bone marrow (referred to as 'transitional' B cells) represent developmental precursors to mature follicular (FO) B lymphocytes, the major mature B cell population in the spleen [2,3]. The other two mature B cell populations consist of non-circulating splenic marginal zone (MZ) B cells that are believed to be derived from transitional cells, and B-1 cells, that are controversial in origin and are enriched in peritoneal and pleural cavities [4]. FO B cells contribute to most T-cell dependent (TD) responses that induce germinal center (GC) development of affinity-matured long lived plasma cells and memory B cells [4,5]. In contrast,
IQGAP1 Interacts with Components of the Slit Diaphragm Complex in Podocytes and Is Involved in Podocyte Migration and Permeability In Vitro  [PDF]
Claire Rigothier, Patrick Auguste, Gavin I. Welsh, Sébastien Lepreux, Colette Deminière, Peter W. Mathieson, Moin A. Saleem, Jean Ripoche, Christian Combe
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037695
Abstract: IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (α-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties.
RBS1, an RNA Binding Protein, Interacts with SPIN1 and Is Involved in Flowering Time Control in Rice  [PDF]
Yuhui Cai, Miguel E. Vega-Sánchez, Chan Ho Park, Maria Bellizzi, Zejian Guo, Guo-Liang Wang
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087258
Abstract: The rice U-box/ARM E3 ubiquitin ligase SPL11 negatively regulates programmed cell death (PCD) and disease resistance, and controls flowering time through interacting with the novel RNA/DNA binding KH domain protein SPIN1. Overexpression of Spin1 causes late flowering in transgenic rice under short-day (SD) and long-day (LD) conditions. In this study, we characterized the function of the RNA-binding and SPIN1-interacting 1 (RBS1) protein in flowering time regulation. Rbs1was identified in a yeast-two-hybrid screen using the full-length Spin1 cDNA as a bait and encodes an RNA binding protein with three RNA recognition motifs. The protein binds RNA in vitro and interacts with SPIN1 in the nucleus. Rbs1 overexpression causes delayed flowering under SD and LD conditions in rice. Expression analyses of flowering marker genes show that Rbs1 overexpression represses the expression of Hd3a under SD and LD conditions. Rbs1 is upregulated in both Spin1 overexpression plants and in the spl11 mutant. Interestingly, Spin1 expression is increased but Spl11 expression is repressed in the Rbs1 overexpression plants. Western blot analysis revealed that the SPIN1 protein level is increased in the Rbs1 overexpression plants and that the RBS1 protein level is also up-regulated in the Spin1 overexpression plants. These results suggest that RBS1 is a new negative regulator of flowering time that itself is positively regulated by SPIN1 but negatively regulated by SPL11 in rice.
Tim50a, a nuclear isoform of the mitochondrial Tim50, interacts with proteins involved in snRNP biogenesis
Hongzhi Xu, Z Brad Somers, Melvin L Robinson, Michael D Hebert
BMC Cell Biology , 2005, DOI: 10.1186/1471-2121-6-29
Abstract: In this report, we identify a minor isoform of the mitochondrial Tim50, Tim50a, as a coilin interacting protein. The Tim50a transcript can be detected in some cancer cell lines and normal brain tissue. The Tim50a protein differs only from Tim50 in that it contains an additional 103 aa N-terminal to the translation start of Tim50. Importantly, a putative nuclear localization signal is found within these 103 residues. In contrast to Tim50, which localizes to the cytoplasm and mitochondria, Tim50a is strictly nuclear and is enriched in speckles with snRNPs. In addition to coilin, Tim50a interacts with snRNPs and SMN. Competition binding experiments demonstrate that coilin competes with Sm proteins of snRNPs and SMN for binding sites on Tim50a.Tim50a may play a role in snRNP biogenesis given its cellular localization and protein interaction characteristics. We hypothesize that Tim50a takes part in the release of snRNPs and SMN from the CB.The biogenesis of most spliceosomal small nuclear ribonucleoproteins (snRNPs) is complicated and requires both cytoplasmic and nuclear maturation steps [1-3]. For example, the spliceosomal small nuclear RNAs (snRNAs) of Ul, U2, U4 and U5 snRNPs are synthesized by RNA polymerase II and may traffic through specific subnuclear domains before being exported to the cytoplasm [1,3]. In the cytoplasm, a septet of Sm proteins (B/B', Dl, D2, D3, E, F, G) binds the Sm motif of the snRNA under the control of the Survival of Motor Neurons (SMN) protein complex. Mutations in the SMN protein cause the neurodegenerative disorder Spinal Muscular Atrophy [4,5]. After the Sm core has been assembled onto the snRNA, the snRNA is subject to further processing, followed by import back into the nucleus; again with the help of the SMN complex [1,5-8].Upon nuclear re-entry, newly assembled Ul, U2, U4 and U5 snRNPs first localize to a subnuclear domain known as the Cajal body [9]. In the Cajal body (CB), the snRNA component of the snRNP is subjected to pseudour
The Gluconeogenesis Pathway Is Involved in Maintenance of Enterohaemorrhagic Escherichia coli O157:H7 in Bovine Intestinal Content  [PDF]
Yolande Bertin, Christiane Deval, Anne de la Foye, Luke Masson, Victor Gannon, Josée Harel, Christine Martin, Micka?l Desvaux, Evelyne Forano
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098367
Abstract: Enterohaemorrhagic Escherichia coli (EHEC) are responsible for outbreaks of food- and water-borne illness. The bovine gastrointestinal tract (GIT) is thought to be the principle reservoir of EHEC. Knowledge of the nutrients essential for EHEC growth and survival in the bovine intestine may help in developing strategies to limit their shedding in bovine faeces thus reducing the risk of human illnesses. To identify specific metabolic pathways induced in the animal GIT, the transcriptome profiles of EHEC O157:H7 EDL933 during incubation in bovine small intestine contents (BSIC) and minimal medium supplemented with glucose were compared. The transcriptome analysis revealed that genes responsible for the assimilation of ethanolamine, urea, agmatine and amino acids (Asp, Thr, Gly, Ser and Trp) were strongly up-regulated suggesting that these compounds are the main nitrogen sources for EHEC in BSIC. A central role for the gluconeogenesis pathway and assimilation of gluconeogenic substrates was also pinpointed in EHEC incubated in BSIC. Our results suggested that three amino acids (Asp, Ser and Trp), glycerol, glycerol 3-phosphate, L-lactate and C4-dicarboxylates are important carbon sources for EHEC in BSIC. The ability to use gluconeogenic substrates as nitrogen sources (amino acids) and/or carbon sources (amino acids, glycerol and lactate) may provide a growth advantage to the bacteria in intestinal fluids. Accordingly, aspartate (2.4 mM), serine (1.9 mM), glycerol (5.8 mM) and lactate (3.6 mM) were present in BSIC and may represent the main gluconeogenic substrates potentially used by EHEC. A double mutant of E. coli EDL933 defective for phosphoenolpyruvate synthase (PpsA) and phosphoenolpyruvate carboxykinase (PckA), unable to utilize tricarboxylic acid (TCA) intermediates was constructed. Growth competition experiments between EHEC EDL933 and the isogenic mutant strain in BSIC clearly showed a significant competitive growth advantage of the wild-type strain further illustrating the importance of the gluconeogenesis pathway in maintaining EHEC in the bovine GIT.
A Tudor Domain Protein SPINDLIN1 Interacts with the mRNA-Binding Protein SERBP1 and Is Involved in Mouse Oocyte Meiotic Resumption  [PDF]
Ting Gang Chew, Anne Peaston, Ai Khim Lim, Chanchao Lorthongpanich, Barbara B. Knowles, Davor Solter
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069764
Abstract: Mammalian oocytes are arrested at prophase I of meiosis, and resume meiosis prior to ovulation. Coordination of meiotic arrest and resumption is partly dependent on the post-transcriptional regulation of maternal transcripts. Here, we report that, SPINDLIN1 (SPIN1), a maternal protein containing Tudor-like domains, interacts with a known mRNA-binding protein SERBP1, and is involved in regulating maternal transcripts to control meiotic resumption. Mouse oocytes deficient for Spin1 undergo normal folliculogenesis, but are defective in resuming meiosis. SPIN1, via its Tudor-like domain, forms a ribonucleoprotein complex with SERBP1, and regulating mRNA stability and/or translation. The mRNA for the cAMP-degrading enzyme, PDE3A, is reduced in Spin1 mutant oocytes, possibly contributing to meiotic arrest. Our study demonstrates that Spin1 regulates maternal transcripts post-transcriptionally and is involved in meiotic resumption.
IAA8 Involved in Lateral Root Formation Interacts with the TIR1 Auxin Receptor and ARF Transcription Factors in Arabidopsis  [PDF]
Fumi Arase, Hiroko Nishitani, Mayumi Egusa, Nami Nishimoto, Sumiko Sakurai, Naho Sakamoto, Hironori Kaminaka
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043414
Abstract: The expression of auxin-responsive genes is regulated by the TIR1/AFB auxin receptor-dependent degradation of Aux/IAA transcriptional repressors, which interact with auxin-responsive factors (ARFs). Most of the 29 Aux/IAA genes present in Arabidopsis have not been functionally characterized to date. IAA8 appears to have a distinct function from the other Aux/IAA genes, due to its unique transcriptional response to auxin and the stability of its encoded protein. In this study, we characterized the function of Arabidopsis IAA8 in various developmental processes governed by auxin and in the transcriptional regulation of the auxin response. Transgenic plants expressing estrogen-inducible IAA8 (XVE::IAA8) exhibited significantly fewer lateral roots than the wild type, and an IAA8 loss-of-function mutant exhibited significantly more. Ectopic overexpression of IAA8 resulted in abnormal gravitropism. The strong induction of early auxin-responsive marker genes by auxin treatment was delayed by IAA8 overexpression. GFP-fusion analysis revealed that IAA8 localized not only to the nucleus, but, in contrast to other Aux/IAAs, also to the cytosol. Furthermore, we demonstrated that IAA8 interacts with TIR1, in an auxin-dependent fashion, and with ARF proteins, both in yeast and in planta. Taken together, our results show that IAA8 is involved in lateral root formation, and that this process is regulated through the interaction with the TIR1 auxin receptor and ARF transcription factors in the nucleus.
GmFT2a, a Soybean Homolog of FLOWERING LOCUS T, Is Involved in Flowering Transition and Maintenance  [PDF]
Hongbo Sun, Zhen Jia, Dong Cao, Bingjun Jiang, Cunxiang Wu, Wensheng Hou, Yike Liu, Zhihong Fei, Dazhong Zhao, Tianfu Han
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0029238
Abstract: Background Flowering reversion can be induced in soybean (Glycine max L. Merr.), a typical short-day (SD) dicot, by switching from SD to long-day (LD) photoperiods. This process may involve florigen, putatively encoded by FLOWERING LOCUS T (FT) in Arabidopsis thaliana. However, little is known about the potential function of soybean FT homologs in flowering reversion. Methods A photoperiod-responsive FT homologue GmFT (renamed as GmFT2a hereafter) was cloned from the photoperiod-sensitive cultivar Zigongdongdou. GmFT2a gene expression under different photoperiods was analyzed by real-time quantitative PCR. In situ hybridization showed direct evidence for its expression during flowering-related processes. GmFT2a was shown to promote flowering using transgenic studies in Arabidopsis and soybean. The effects of photoperiod and temperature on GmFT2a expression were also analyzed in two cultivars with different photoperiod-sensitivities. Results GmFT2a expression is regulated by photoperiod. Analyses of GmFT2a transcripts revealed a strong correlation between GmFT2a expression and flowering maintenance. GmFT2a transcripts were observed continuously within the vascular tissue up to the shoot apex during flowering. By contrast, transcripts decreased to undetectable levels during flowering reversion. In grafting experiments, the early-flowering, photoperiod-insensitive stock Heihe27 promotes the appearance of GmFT2a transcripts in the shoot apex of scion Zigongdongdou under noninductive LD conditions. The photothermal effects of GmFT2a expression diversity in cultivars with different photoperiod-sensitivities and a hypothesis is proposed. Conclusion GmFT2a expression is associated with flowering induction and maintenance. Therefore, GmFT2a is a potential target gene for soybean breeding, with the aim of increasing geographic adaptation of this crop.
The G Protein Coupled Receptor 3 Is Involved in cAMP and cGMP Signaling and Maintenance of Meiotic Arrest in Porcine Oocytes  [PDF]
Cai-Rong Yang, Yanchang Wei, Shu-Tao Qi, Lei Chen, Qing-Hua Zhang, Jun-Yu Ma, Yi-Bo Luo, Ya-Peng Wang, Yi Hou, Heide Schatten, Zhong-Hua Liu, Qing-Yuan Sun
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038807
Abstract: The arrest of meiotic prophase in mammalian oocytes within fully grown follicles is dependent on cyclic adenosine monophosphate (cAMP) regulation. A large part of cAMP is produced by the Gs-linked G-protein-coupled receptor (GPR) pathway. In the present study, we examined whether GPR3 is involved in the maintenance of meiotic arrest in porcine oocytes. Expression and distribution of GPR3 were examined by western blot and immunofluorescence microscopy, respectively. The results showed that GPR3 was expressed at various stages during porcine oocyte maturation. At the germinal vesicle (GV) stage, GPR3 displayed a maximal expression level, and its expression remained stable from pro-metaphase I (MI) to metaphase II (MII). Immunofluorescence staining showed that GPR3 was mainly distributed at the nuclear envelope during the GV stage and localized to the plasma membrane at pro-MI, MI and MII stages. RNA interference (RNAi) was used to knock down the GPR3 expression within oocytes. Injection of small interfering double-stranded RNA (siRNA) targeting GPR3 stimulated meiotic resumption of oocytes. On the other hand, overexpression of GPR3 inhibited meiotic maturation of porcine oocytes, which was caused by increase of cGMP and cAMP levels and inhibition of cyclin B accumulation. Furthermore, incubation of porcine oocytes with the GPR3 ligand sphingosylphosphorylcholine (SPC) inhibited oocyte maturation. We propose that GPR3 is required for maintenance of meiotic arrest in porcine oocytes through pathways involved in the regulation of cAMP and cGMP.
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