1
|
Sahmi F, Sahmi M, Gévry N, Sahadevan P, Allen BG, Price CA. A putative protein-RNA complex regulates posttranscriptional processing of cytochrome P450 aromatase (CYP19A1) in bovine granulosa cells. Mol Reprod Dev 2019; 86:1901-1908. [PMID: 31713287 DOI: 10.1002/mrd.23289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 10/08/2019] [Indexed: 12/30/2022]
Abstract
Follicle growth and granulosa cell health are dependent on the secretion of estradiol from granulosa cells. Estradiol is synthesized from androgen precursor by cytochrome P450 aromatase (CYP19A1), and in cattle CYP19A1 messenger RNA has a short half-life but a long (3.5 kb) 3'-untranslated region (3'UTR), suggesting that posttranscriptional regulation may be important for control of enzyme activity. We tested this hypothesis by inserting the CYP19A1 3'UTR and fragments thereof into a reporter vector between the end of the luciferase coding region and the polyadenylation signal. The full-length aromatase 3'UTR suppressed luciferase activity to 10% of control levels, and smaller fragments showed that this inhibitory activity lies between +926 and +1134 of the 3'UTR. Protein-RNA cross-linking experiments revealed that these 3'UTR fragments formed an RNA-protein complex of approximately 70 kDa that was present in granulosa cells but not in corpus luteum, lung, liver, kidney, pancreas, or bladder extracts. The RNA-binding activity was specific to the 3'UTR, as shown by competition experiments with unlabeled RNA, and was present only in 3'UTR constructs that inhibited luciferase activity. These data suggest that posttranscriptional regulation is an important component of the control of CYP19A1 expression and involves protein binding to a specific sequence in the 3'UTR.
Collapse
Affiliation(s)
- Fatiha Sahmi
- Centre de Recherche en Reproduction et Fertilité, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.,Département de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Malha Sahmi
- Centre de Recherche en Reproduction et Fertilité, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.,Institut de Recherche en Immunologie et en Cancérologie, Université de Montréal, Montréal, Québec, Canada
| | - Nicolas Gévry
- Centre de Recherche en Reproduction et Fertilité, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.,Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Pramod Sahadevan
- Département de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Bruce G Allen
- Département de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Christopher A Price
- Centre de Recherche en Reproduction et Fertilité, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada
| |
Collapse
|
2
|
Chen F, Shyu AB, Shneider BL. Hu antigen R and tristetraprolin: counter-regulators of rat apical sodium-dependent bile acid transporter by way of effects on messenger RNA stability. Hepatology 2011; 54:1371-8. [PMID: 21688286 PMCID: PMC3205920 DOI: 10.1002/hep.24496] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 06/06/2011] [Indexed: 01/08/2023]
Abstract
UNLABELLED The apical sodium-dependent bile acid transporter (ASBT, SLC10A2) mediates intestinal, renal, and cholangiocyte bile acid reclamation. Transcriptional regulation of ASBT is well described, whereas information on posttranscriptional regulation is limited. Prior studies suggested that ontogeny of ASBT is controlled in part by changes in messenger RNA (mRNA) stability. We studied the role that Hu antigen R (HuR) and tristetraprolin (TTP) play in regulating the expression of mRNA that contains the 3' untranslated region (UTR) of rat ASBT. The 3'UTR was incorporated into an SV-40 driven luciferase reporter (rASBT3-luciferase) for rapid screening of regulatory effects. Silencing HuR reduced luciferase reporter activity, whereas silencing TTP enhanced luciferase activity. Conversely, overexpression of HuR enhanced rASBT3-luciferase reporter activity. The same 3'UTR fragments of rat ASBT were incorporated into a beta-globin coding mRNA construct for analysis of mRNA stability (rASBT3-βglobin). mRNA half-life was progressively shortened by the incorporation of increasing sized fragments of the 3'UTR. Silencing HuR shortened the half-life of rASBT3-βglobin containing 0.3 kb of the rat ASBT 3'UTR. Gel shift assays revealed binding of HuR and TTP to rat ASBT 3'UTR. Endogenously expressed human ASBT mRNA half-lives and steady-state protein levels in Caco-2 cells were repressed when HuR was silenced but was enhanced when TTP was silenced. Developmental changes in HuR and TTP protein abundance correlated with previously characterized ontogenic changes in rat ileal and renal ASBT expression. CONCLUSION These studies not only show that ASBT expression is controlled at the level of mRNA stability by way of its 3'UTR, but also identify HuR and TTP as two key transacting factors that are involved in exerting counterregulatory effects on ASBT mRNA stability.
Collapse
Affiliation(s)
- Frank Chen
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh PA, 15224
| | - Ann-Bin Shyu
- Department of Biochemistry and Molecular Biology, The University of Texas Medical School, Houston, TX, 77030
| | - Benjamin L. Shneider
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh PA, 15224
| |
Collapse
|
3
|
Cannon JD, Seekallu SV, Vandevoort CA, Chaffin CL. Association of luteinizing hormone receptor gene expression with cell cycle progression in granulosa cells. Am J Physiol Endocrinol Metab 2009; 296:E1392-9. [PMID: 19293332 PMCID: PMC2692403 DOI: 10.1152/ajpendo.90965.2008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During hormonally induced ovarian follicle growth, granulosa cell proliferation increases and returns to baseline prior to the administration of an ovulatory stimulus. Several key genes appear to follow a similar pattern, including the luteinizing hormone receptor (LHCGR), suggesting an association between cell cycle progression and gene expression. The expression of LHCGR mRNA in granulosa cells isolated from immature rats and treated in culture with FSH increased in a time-dependent manner, whereas administration of the cell cycle inhibitor mimosine completely suppressed expression. Although forskolin was able to induce luteinization in cells treated with mimosine, human chorionic gonadotropin had no effect, indicating the functional loss of LHCGR. The effects of mimosine on cell cycle progression and LHCGR mRNA expression were reversible within 24 h of mimosine removal. Cell cycle inhibition did not alter the stability of LHCGR mRNA, indicating that the primary effect was at the transcriptional level. To determine whether the relationship between LHCGR expression and cell cycle were relevant in vivo, immature rats were given a bolus of PMSG, followed by a second injection of either saline or PMSG 24 h later to augment levels of proliferation. The expression of LHCGR mRNA was elevated in the ovaries of animals receiving a supplement of PMSG. Mimosine also blocked cell cycle progression and LHCGR mRNA expression in macaque granulosa cells isolated following controlled ovarian stimulation cycles and in two different mouse Leydig tumor lines. These data collectively indicate that LHCGR mRNA is expressed as a function of the passage of cells across the G1-S phase boundary.
Collapse
Affiliation(s)
- Jennifer D Cannon
- Dept. of Obstetrics, Gynecology, & Reproductive Sciences, Univ. of Maryland School of Medicine, Baltimore, MD 21201, USA
| | | | | | | |
Collapse
|
4
|
Mak IWY, Liu L, Ling V, Kastelic T. The effect of the fungal metabolite radicicol analog A on mRNA degradation. Genomics 2007; 90:723-32. [PMID: 17936575 DOI: 10.1016/j.ygeno.2007.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 07/09/2007] [Accepted: 08/06/2007] [Indexed: 12/30/2022]
Abstract
The AU-rich element (ARE) is a stability determinant found in the 3' UTR of a number of short-lived mRNAs. The best characterized ARE is the Shaw-Kamen (SK) box or AUUUA motif. Previously, a fungal metabolite, radicicol analog A (RAA), was shown to destabilize SK box-containing mRNAs based on 16 mRNAs examined [T. Kastelic et al., Cytokine 8 (1996) 751-761]. Using serial analysis of gene expression (SAGE) to examine the global effect of RAA on mRNA expression in interferon-gamma/lipopolysaccharide-stimulated THP-1 human monocytes, we observed that the expression level of greater than 99% of the SAGE tags was unchanged by RAA treatment and only 34 of the 17,608 unique tags annotated were reduced (p< or =0.0001). RAA destabilized approximately half of the down-regulated transcripts. Whereas all the destabilized mRNAs possessed at least one SK box, for transcripts not destabilized but nonetheless down-regulated, RAA appears to function by a SK box-independent mechanism not currently understood.
Collapse
Affiliation(s)
- Isabella W Y Mak
- BC Cancer Research Centre, BC Cancer Agency, Vancouver, BC, Canada
| | | | | | | |
Collapse
|
5
|
Eberhardt W, Doller A, Akool ES, Pfeilschifter J. Modulation of mRNA stability as a novel therapeutic approach. Pharmacol Ther 2007; 114:56-73. [PMID: 17320967 DOI: 10.1016/j.pharmthera.2007.01.002] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 01/10/2007] [Accepted: 01/10/2007] [Indexed: 12/21/2022]
Abstract
During the last decade evidence has accumulated that modulation of mRNA stability plays a central role in cellular homeostasis, including cell differentiation, proliferation and adaptation to external stimuli. The functional relevance of posttranscriptional gene regulation is highlighted by many pathologies, wherein occurrence tightly correlates with a dysregulation in mRNA stability, including chronic inflammation, cardiovascular diseases and cancer. Most commonly, the cis-regulatory elements of mRNA decay are represented by the adenylate- and uridylate (AU)-rich elements (ARE) which are specifically bound by trans-acting RNA binding proteins, which finally determine whether mRNA decay is delayed or facilitated. Regulation of mRNA decay by RNA stabilizing and RNA destabilizing factors is furthermore controlled by different intrinsic and environmental stimuli. The modulation of mRNA binding proteins, therefore, illuminates a promising approach for the pharmacotherapy of those key pathologies mentioned above and characterized by a posttranscriptional dysregulation. Most promisingly, intracellular trafficking of many of the mRNA stability regulating factors is, in turn, regulated by some major signaling pathways, including the mitogen-activated protein kinase (MAPK) cascade, the AMP-activated kinase (AMPK) and the protein kinase (PK) C (PKC) family. In this review, we present timely examples of genes regulated by mRNA stability with a special focus on signaling pathways involved in the ARE-dependent mRNA decay. A better understanding of these processes may form the basis for the development of novel therapeutics to treat major human diseases.
Collapse
Affiliation(s)
- Wolfgang Eberhardt
- Pharmazentrum frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
| | | | | | | |
Collapse
|
6
|
Abstract
The alpha-synuclein (Snca) gene is expressed at higher levels in alcohol-naïve, inbred alcohol-preferring (iP) rats than in alcohol-non preferring (iNP) rats. Snca modulates dopamine transmission and the dopamineregic system, which play a role in mediating the rewarding properties of alcohol consumption. Thus, understanding regulation of Snca gene expression could provide insight into the relationship of Snca and alcohol consumption. To study regulation of rat Snca expression, 1,912 bp of the iP and iNP 5'-regions were cloned and sequenced. 5'-rapid amplification of cDNA ends (RACE), primer extension and RT-PCR mapped three transcription start site clusters (clusters TSS1, TSS2 and TSS3), suggesting that the Snca proximal promoter region has a complex architecture. This proximal promoter region has three TATA-less core promoters containing SP1 binding sites, initiator elements and downstream core promoter elements, which are often located in such promoters. Snca-luc constructs transiently transfected into SK-N-SH neuroblastoma cells showed that the region from - 1,912 to - 1,746 contained a strong core promoter, and that the entire approximately 2 kb region had significant promoter activity. Five polymorphisms identified between the iP and iNP in the proximal promoter region did not influence differential expression between the strains. In contrast, a single nucleotide polymorphism (SNP) at + 679 in the 3'-untranslated region (UTR) resulted in a 1.3-fold longer half-life of iP mRNA compared with iNP mRNA, which is consistent with the differential expression observed between the iP and iNP strains. These results suggest that regulation of rat Snca gene expression is complex and may contribute to alcohol preference in the iP rats.
Collapse
MESH Headings
- 3' Untranslated Regions/drug effects
- 3' Untranslated Regions/physiology
- Alcohol-Induced Disorders, Nervous System/genetics
- Alcohol-Induced Disorders, Nervous System/metabolism
- Alcohol-Induced Disorders, Nervous System/physiopathology
- Alcoholism/genetics
- Alcoholism/metabolism
- Alcoholism/physiopathology
- Animals
- Base Sequence/genetics
- Brain/drug effects
- Brain/metabolism
- Brain/physiopathology
- Cell Line, Tumor
- Central Nervous System Depressants/adverse effects
- Choice Behavior
- Disease Models, Animal
- Dopamine/metabolism
- Ethanol/adverse effects
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- HeLa Cells
- Humans
- Neural Pathways/drug effects
- Neural Pathways/metabolism
- Neural Pathways/physiopathology
- Polymorphism, Single Nucleotide/drug effects
- Polymorphism, Single Nucleotide/genetics
- Promoter Regions, Genetic/drug effects
- Promoter Regions, Genetic/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Regulatory Elements, Transcriptional/genetics
- Species Specificity
- alpha-Synuclein/biosynthesis
- alpha-Synuclein/drug effects
- alpha-Synuclein/genetics
Collapse
Affiliation(s)
- Tiebing Liang
- Department of Medicine, Indiana University School of Medicine, Indianapolis, 46202, USA
| | | |
Collapse
|
7
|
SPENCE JP, LIANG T, HABEGGER K, CARR LG. Effect of polymorphism on expression of the neuropeptide Y gene in inbred alcohol-preferring and -nonpreferring rats. Neuroscience 2005; 131:871-6. [PMID: 15749341 PMCID: PMC4455873 DOI: 10.1016/j.neuroscience.2004.10.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2004] [Indexed: 11/22/2022]
Abstract
Using animal models of alcoholism, previous studies suggest that neuropeptide Y (NPY) may be implicated in alcohol preference and consumption due to its role in the modulation of feeding and anxiety. Quantitative trait loci (QTL) analysis previously identified an interval on rat chromosome 4 that is highly associated with alcohol preference and consumption using an F2 population derived from inbred alcohol-preferring (iP) and -nonpreferring (iNP) rats. NPY mapped to the peak of this QTL region and was prioritized as a candidate gene for alcohol-seeking behavior in the iP and iNP rats. In order to identify a potential mechanism for reduced NPY protein levels documented in the iP rat, genetic and molecular components that influence NPY expression were analyzed between iP and iNP rats. Comparing the iP rat to the iNP rat, quantitative real-time polymerase chain reaction detected significantly decreased levels of NPY mRNA expression in the iP rat in the six brain regions tested: nucleus accumbens, frontal cortex, amygdala, hippocampus, caudate-putamen, and hypothalamus. In addition, the functional significance of three previously identified polymorphisms was assessed using in vitro expression analysis. The polymorphism defined by microsatellite marker D4Mit7 in iP rats reduced luciferase reporter gene expression in SK-N-SH neuroblastoma cells. These results suggest that differential expression of the NPY gene resulting from the D4mit7 marker polymorphism may contribute to reduced levels of NPY in discrete brain regions in the iP rats.
Collapse
Affiliation(s)
| | | | | | - L. G. CARR
- Corresponding author. Tel: +-317-274-0152; fax: +1-317-274-2695. (L. G. Carr)
| |
Collapse
|
8
|
Liang T, Habegger K, Spence JP, Foroud T, Ellison JA, Lumeng L, Li TK, Carr LG. Glutathione S-transferase 8-8 expression is lower in alcohol-preferring than in alcohol-nonpreferring rats. Alcohol Clin Exp Res 2005; 28:1622-8. [PMID: 15547447 PMCID: PMC4455766 DOI: 10.1097/01.alc.0000145686.79141.57] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE A primary focus of alcohol research is to provide novel targets for alcohol treatment by identifying genes that predispose individuals to drink alcohol. Animal models of alcoholism developed by selective breeding are invaluable tools to elucidate both the genetic nature and the underlying biological mechanisms that contribute to alcohol dependence. These selected lines (high alcohol preferring and low alcohol preferring) display phenotypic and genetic differences that can be studied to further our understanding of alcohol preference and related genetic traits. By combining molecular techniques, genetic and physiological factors that underlie the cause of alcoholism can be identified. METHODS Total gene expression analysis was used to identify genes that are differentially expressed in specific brain regions between alcohol-naive, inbred alcohol-preferring (iP) and -nonpreferring (iNP) rats. Quantitative reverse transcriptase-polymerase chain reaction, in situ hybridization, Western blot, and sequence analysis were used to further characterize rat glutathione S-transferase 8-8 (rGST 8-8). RESULTS Lower expression of rGST 8-8 mRNA was observed in discrete brain regions of iP compared with iNP animals, and these expression differences were confirmed. To determine additional expression patterns of rGST 8-8, we used in situ hybridization. Rat GST 8-8 was highly expressed in hippocampus, the choroid plexus of the dorsal third ventricle and the lateral ventricle, and ependymal cells along the dorsal third ventricle and the third ventricle. Western blot analysis showed that rGST 8-8 protein levels were lower in the hippocampus and the amygdala of iP compared with iNP. A silent single-nucleotide polymorphism in the coding region and three single-nucleotide polymorphisms in the 3'-UTR were identified in the rGST 8-8 cDNA. CONCLUSION There is regional variation of rGST 8-8 expression in the brain, at both the mRNA and protein level, and the iP strain has lower innate rGST 8-8 levels than the iNP strain in discrete brain regions.
Collapse
Affiliation(s)
- Tiebing Liang
- Department of Medicine, Indiana University School of Medicine, 975 W. Walnut Street, Indianapolis, IN 46202, USA
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Menon KMJ, Munshi UM, Clouser CL, Nair AK. Regulation of luteinizing hormone/human chorionic gonadotropin receptor expression: a perspective. Biol Reprod 2004; 70:861-6. [PMID: 14668203 DOI: 10.1095/biolreprod.103.024471] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The LH/hCG receptor, a member of the G protein coupled receptor family mediates the cellular actions of LH in the ovary. A considerable amount of information regarding its structure, mechanism of activation, and regulation of expression has emerged in recent years. Here we provide a brief overview of the current information on the structural organization of the receptor and the mechanism of receptor mediated signaling as well as an in-depth discussion on recent developments pertaining to the regulation of receptor expression. Specifically, we describe studies from our laboratory showing that the posttranscriptional regulation of the receptor involves an LH/hCG receptor mRNA-binding protein. We also propose a model to explain the loss of steady-state LH/hCG receptor mRNA levels during receptor down-regulation.
Collapse
Affiliation(s)
- K M J Menon
- Departments of Obstetrics and Gynecology and Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
| | | | | | | |
Collapse
|
10
|
Liang T, Spence J, Liu L, Strother WN, Chang HW, Ellison JA, Lumeng L, Li TK, Foroud T, Carr LG. alpha-Synuclein maps to a quantitative trait locus for alcohol preference and is differentially expressed in alcohol-preferring and -nonpreferring rats. Proc Natl Acad Sci U S A 2003; 100:4690-5. [PMID: 12665621 PMCID: PMC153617 DOI: 10.1073/pnas.0737182100] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Total gene expression analysis (TOGA) was used to identify genes that are differentially expressed in brain regions between the alcohol-naive, inbred alcohol-preferring (iP), and -nonpreferring (iNP) rats. alpha-Synuclein, expressed at >2-fold higher levels in the hippocampus of the iP than the iNP rat, was prioritized for further study. In situ hybridization was used to determine specific brain regions and cells expressing alpha-synuclein in the iP and iNP rats. Similar to alpha-synuclein mRNA levels, protein levels in the hippocampus were higher in iP rats than iNP rats. Higher protein levels were also observed in the caudate putamen of iP rats compared with iNP rats. Sequence analysis identified two single nucleotide polymorphisms in the 3' UTR of the cDNA. The polymorphism was used to map the gene, by using recombination-based methods, to chromosome 4, within a quantitative trait locus for alcohol consumption that was identified in the iP and iNP rats. A nucleotide exchange in the iNP 3' UTR reduced expression of the luciferase reporter gene in SK-N-SH neuroblastoma cells. These results suggest that differential expression of the alpha-synuclein gene may contribute to alcohol preference in the iP rats.
Collapse
Affiliation(s)
- Tiebing Liang
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Guo C, Savage L, Sarge KD, Park-Sarge OK. Gonadotropins decrease estrogen receptor-beta messenger ribonucleic acid stability in rat granulosa cells. Endocrinology 2001; 142:2230-7. [PMID: 11356667 DOI: 10.1210/endo.142.6.8102] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have previously shown that the preovulatory LH surge down-regulates estrogen receptor-beta (ERbeta) messenger RNA (mRNA) levels selectively in the granulosa cells of preovulatory follicles. To gain insight into the underlying mechanisms, we examined whether the LH-induced loss of ERbeta mRNA expression in rat granulosa cells is attributable to the hormone-induced changes at the level of transcription and/or mRNA degradation. When the rate of ERbeta gene transcription was assessed in cultured granulosa cells, by nuclear run-off assays, we observed only a marginal effect of hCG on ERbeta gene transcription. In contrast, when ERbeta mRNA levels were estimated in granulosa cells that were cultured in the presence of 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), an RNA synthesis inhibitor, we observed a significant inhibitory effect of human CG (hCG) on ERbeta mRNA expression at a magnitude similar to that observed in the absence of DRB. Forskolin (FSK) and 2-O-tetradecanol-phorbol-13-acetate (TPA), pharmacological agents that mimic LH actions in granulosa cells, also showed similar effects. Thus, these results suggest that LH decreases ERbeta mRNA expression in the granulosa cells of preovulatory follicles, primarily by destabilizing the preexisting ERbeta mRNA. We next determined the decay rate of the ERbeta mRNA in granulosa cells that were cultured in the presence of DRB and additional hCG, FSK, or TPA for various time periods, by estimating ERbeta mRNA levels, using semiquantitative RT-PCR assays and subsequent linear regression analyses. The half-life of the ERbeta mRNA in the presence of vehicle was 17.87 +/- 1.2 h (n = 4). hCG dramatically decreased the half-life of the ERbeta mRNA (4.85 +/- 0.49 h, n = 4). Similarly, both FSK and TPA decreased the half-life of the ERbeta mRNA to 3.57 +/- 0.31 h and 4.02 +/- 0.13 h, respectively. We extended these findings by examining whether the LH-induced down-regulation of the ERbeta mRNA is cycloheximide-sensitive. When granulosa cells were cultured in the presence of cycloheximide, a protein synthesis inhibitor, the inhibitory effects of hCG, FSK, and TPA on ERbeta mRNA levels were abolished. Similar results were obtained in the presence or absence of DRB, indicating that the hormone-induced destabilization of the ERbeta mRNA is coupled with translation processes. Taken together, our results demonstrate that LH decreases ERbeta mRNA expression, predominantly at the posttranscriptional level, in a cycloheximide-sensitive manner.
Collapse
Affiliation(s)
- C Guo
- Department of Physiology, University of Kentucky, Lexington 40536-0084, USA
| | | | | | | |
Collapse
|
12
|
Song X, Singh SM. Distribution and molecular characterization of mRNA-binding proteins specific to the (U)15 region of 3' UTR of the mouse catalase (Cas-1). DNA Cell Biol 2001; 20:339-48. [PMID: 11445005 DOI: 10.1089/10445490152122451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The 3' UTR of the mouse Cas-1 mRNA, encoding the antioxidant enzyme catalase, has a U-rich motif that is conserved across species. This motif is an active site for complex and dynamic interactions involving RNA-binding proteins. The spatial, temporal, and phylogenetic distribution of the Cas-1 3'-UTR U-rich motif-specific RNA-binding proteins was evaluated by gel mobility shift and UV cross-linking assays. The specific RNA-protein complexes were observed in mouse tissue homogenates representing developmental stages as early as day 10 pc and ranged in molecular weight from approximately 38 kDa to approximately 52 kDa. These mRNA-protein complexes appeared in all vertebrate species examined (human, mouse, rat, dog, rabbit, chicken, fish, and frog) but not in insects. The approximately 38-kDa protein was the most prominent protein in vertebrates. The cDNA sequence of the mouse approximately 38-kDa protein was obtained by purification of the protein, microsequencing, and RT-PCR. The resulting 456-nt sequence, representing the partial internal cDNA sequence, and its deduced amino acid sequence were similar to the RNA recognition motif (RRM) of a protein superfamily, implicated in splicing, stability, localization, and translation of RNAs. Although the results suggest that cis element-binding activity could be a cytoplasmic regulator of Cas-1 mRNA metabolism, the significance of this binding remains to be determined.
Collapse
Affiliation(s)
- X Song
- Molecular Genetics Unit, Department of Zoology and Division of Medical Genetics, The University of Western Ontario, London, Ontario, Canada
| | | |
Collapse
|
13
|
Abstract
Intestinal reabsorption of bile salts plays a crucial role in human health and disease. This process is primarily localized to the terminal ileum and is mediated by a 48-kd sodium-dependent bile acid cotransporter (SLC10A2 = ASBT). ASBT is also expressed in renal tubule cells, cholangiocytes, and the gallbladder. Exon skipping leads to a truncated version of ASBT, which sorts to the basolateral surface and mediates efflux of bile salts. Inherited mutation of ASBT leads to congenital diarrhea secondary to bile acid malabsorption. Partial inhibition of ASBT may be useful in the treatment of hypercholesterolemia and intrahepatic cholestasis. During normal development in the rat ileum, ASBT undergoes a biphasic pattern of expression with a prenatal onset, postnatal repression, and reinduction at the time of weaning. The bile acid responsiveness of the ASBT gene is not clear and may be dependent on both the experimental model used and the species being investigated. Future studies of the transcriptional and posttranscriptional regulation of the ASBT gene and analysis of ASBT knockout mice will provide further insight into the biology, physiology, and pathophysiology of intestinal bile acid transport.
Collapse
Affiliation(s)
- B L Shneider
- Mount Sinai Medical Center, New York, NY 10029, USA
| |
Collapse
|