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At least 721 records · Page 40Linked to original sources
PubMed1994

Mechanisms regulating the mRNA levels of interleukin-5 and two other coordinately expressed lymphokines in the murine T lymphoma EL4.23.

The mechanisms that regulate the mRNA levels of interleukin-5 (IL-5) were compared with those regulating the mRNA levels of two other coordinately expressed lymphokines in the murine T lymphoma EL4.23. Our results indicate that IL-5 mRNA levels are independently regulated from those of IL-2 and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNAs. The induction of IL-5 mRNA by phorbol 12-myristate 13-acetate (PMA) stimulation was found to be cyclosporin A-resistant, in contrast to the induction of IL-2 and GM-CSF mRNAs. Although the three lymphokine mRNAs were not detected in unstimulated cells by Northern blot analysis, the GM-CSF gene was found by nuclear run-off analysis to be constitutively transcribed. However, the IL-2 and IL-5 genes were transcriptionally inactive in the absence of PMA stimulation. The induction of IL-5 mRNA by PMA stimulation primarily involved increased transcriptional activity. In contrast, GM-CSF mRNA induction predominantly involved enhanced mRNA stability. Both transcriptional and mRNA stabilization mechanisms appeared to regulate IL-2 mRNA induction. The activation of IL-2 and IL-5 gene transcription was dependent on de novo protein synthesis. Cellular treatment with cycloheximide enhanced IL-2 gene transcription once activation was initiated, implicating the involvement of a labile repressor(s). Furthermore, IL-5 mRNA was more stable than IL-2 and GM-CSF mRNAs. These latter two species were stabilized by cycloheximide, suggesting that a labile mechanism may regulate their degradation.

Animals↗
PubMed2004

The role of mRNA turnover in the regulation of tristetraprolin expression: evidence for an extracellular signal-regulated kinase-specific, AU-rich element-dependent, autoregulatory pathway.

Tristetraprolin (TTP) is a regulator of TNF-alpha mRNA stability and is the only trans-acting factor shown to be capable of regulating AU-rich element-dependent mRNA turnover at the level of the intact animal. Using the THP-1 myelomonocytic cell line, we demonstrated for the first time that TTP is encoded by an mRNA with a short half-life under resting conditions. Using pharmacologic inhibitors of the mitogen-activated protein kinase pathways, we show that the induction of TTP by LPS activation is mediated through changes in transcription, mRNA stability, and translation. A coordinate increase in both TTP and TNF-alpha mRNA stability occurs within 15 min of LPS treatment, but is transduced through different mitogen-activated protein kinase pathways. This regulation of TTP and TNF-alpha mRNA stability is associated with the finding that TTP binds these mRNA under both resting and LPS-activated conditions in vivo. Finally, we demonstrate that TTP can regulate reporter gene expression in a TTP 3' untranslated region-dependent manner and identify three distinct AU-rich elements necessary to mediate this effect. Thus, TTP regulates its own expression in a manner identical to that seen with the TNF-alpha 3' untranslated region, indicating that this autoregulation is mediated at the level of mRNA stability. In this manner, TTP is able to limit the production of its own proteins as well as that of TNF-alpha and thus limit the response of the cell to LPS.

Cell Line↗
PubMed2004

Genomic run-on evaluates transcription rates for all yeast genes and identifies gene regulatory mechanisms.

Most studies of eukaryotic gene regulation have been done looking at mature mRNA levels. Nevertheless, the steady-state mRNA level is the result of two opposing factors: transcription rate (TR) and mRNA degradation. Both can be important points to regulate gene expression. Here we show a new method that combines the use of nylon macroarrays and in vivo radioactive labeling of nascent RNA to quantify TRs, mRNA levels, and mRNA stabilities for all the S. cerevisiae genes. We found that during the shift from glucose to galactose, most genes undergo drastic changes in TR and mRNA stability. However, changes in mRNA levels are less pronounced. Some genes, such as those encoding mitochondrial proteins, are coordinately regulated in mRNA stability behaving as decay regulons. These results indicate that, although TR is the main determinant of mRNA abundance in yeast, modulation of mRNA stability is a key factor for gene regulation.

Blotting, Northern↗
PubMed1991

Stability changes in pim-1 proto-oncogene mRNA after mitogen stimulation of normal lymphocytes.

mRNA expression of the serine/threonine kinase protooncogene Pim-1 was investigated in mitogen-treated normal bovine lymphocytes. After stimulation with Con A and phorbol ester (PMA), normal bovine PBMC exhibited a 3.5-fold induction of pim-1 mRNA within 4 h of stimulation. By 17 h poststimulation, however, the level of pim-1 mRNA had fallen to approximately 50%. Similar transient kinetics of pim-1 expression were also observed in mitogen-stimulated bovine lymph node lymphocytes and the amount of pim-1 mRNA induced was dependent on the type of mitogen stimulus. Typically, stimulation with Con A and PMA together acted synergistically resulting in a greatly increased amount of pim-1 mRNA induction compared to stimulation with either Con A or PMA alone. To determine if an increase in pim-1 mRNA stability contributed to the overall increase in pim-1 mRNA levels observed after mitogen stimulation, RNA half-life studies were performed. At 4 h poststimulation, pim-1 mRNA in bovine lymph node lymphocytes was relatively stable with a t1/2 of approximately 80 min; at 17 h poststimulation, however, the t1/2 (approximately 35 min) was markedly decreased. In addition, cyclohexamide treatment was found to markedly increase the stability of pim-1 transcripts in bovine PBMC suggesting that a protein synthesis-dependent posttranscriptional pim-1 mRNA degradation pathway may be involved in the regulation of pim-1 mRNA levels in lymphoid cells. To investigate the possible contribution of the destabilizing (UAUU)n motif to pim-1 mRNA stability, the t1/2 of the short 2.4-kb germ cell-specific pim-1 transcript found in rat testes was compared to that of the longer 2.8-kb somatic transcript expressed in stimulated rat lymphocytes. t1/2 determination experiments showed that the 2.4-kb testes-specific transcript, which is missing the destabilizing (UAUU)n sequence, was quite stable (t1/2 much greater than 6 h). In contrast, the t1/2 of the longer 2.8 kb somatic cell pim-1 transcript that contains this A/U-rich sequence motif was found to be much shorter (t1/2 approximately 130 min) in mitogen-activated rat lymphocytes. Together these findings indicate that the transient induction of pim-1 gene expression is associated with normal lymphocyte activation and that the stability of pim-1 transcripts is regulated in lymphocytes during the course of activation. In addition, the differences in pim-1 mRNA stability observed in germ cells and lymphocytes of the same animal are likely the result of molecular mechanisms involving differential regulation by the message destabilizing (UAUU)n motif.

Animals↗
PubMed1983

Estrogen stabilizes vitellogenin mRNA against cytoplasmic degradation.

We have demonstrated, by DNA excess filter hybridizations to pulse-labeled cell RNA, that estrogen selectively stabilizes Xenopus liver vitellogenin mRNA against cytoplasmic degradation. The half-life of vitellogenin mRNA is approximately 3 weeks in the presence of estrogen and 16 hr after estrogen is withdrawn from the culture medium. Total poly(A) mRNA exhibits the same half-life (16 hr) in the presence or absence of estrogen. The rapid cytoplasmic degradation of vitellogenin mRNA in the absence of estrogen is fully reversible upon restimulation with estrogen, indicating that nuclear modification of vitellogenin RNA transcripts is not responsible for their stability. Intermediate levels of vitellogenin mRNA stability and changes in the relative rate of vitellogenin gene transcription are not observed late in estrogen induction, when vitellogenin mRNA levels plateau. Instead, Xenopus liver cells achieve fine control over the level of vitellogenin mRNA through down-regulation of the overall rate of total nuclear RNA synthesis.

Animals↗
PubMed2001

Granulocyte macrophage-colony-stimulating factor mRNA is stabilized in airway eosinophils and peripheral blood eosinophils activated by TNF-alpha plus fibronectin.

Airway eosinophils show prolonged in vitro survival compared with peripheral blood eosinophils (PBEos). Recent studies have shown that autocrine production and release of GM-CSF is responsible for enhanced survival, but the mechanisms controlling cytokine production remain obscure. We compared GM-CSF mRNA decay in eosinophils from bronchoalveolar lavage (BALEos) after allergen challenge or from PBEos. BALEos showed prolonged survival in vitro (60% at 4 days) and expressed GM-CSF mRNA. The enhanced survival of BALEos was 75% inhibited at 6 days by neutralizing anti-GM-CSF Ab. Based on transfection studies, GM-CSF mRNA was 2.5 times more stable in BALEos than in control PBEos. Treatment of PBEos with fibronectin and TNF-alpha increased their in vitro survival, GM-CSF mRNA expression, and GM-CSF mRNA stability to a comparable level as seen in BALEos. These data suggest that TNF-alpha plus fibronectin may increase eosinophil survival in vivo by controlling GM-CSF production at a posttranscriptional level.

Bronchi↗
PubMed1997

Enhanced stability of urokinase-type plasminogen activator mRNA in metastatic breast cancer MDA-MB-231 cells and LLC-PK1 cells down-regulated for protein kinase C--correlation with cytoplasmic heterogeneous nuclear ribonucleoprotein C.

In LLC-PK1 cells, urokinase-type plasminogen activator (uPA) mRNA has a short half-life of 70 min. We have previously demonstrated that most of the regulatory regions responsible for the rapid turnover of uPA mRNA in LLC-PK1 cells reside in its 3' untranslated region (3' UTR), where there are at least three regulatory sites, one of which is A+U-rich. This A+U-rich sequence mediates uPA mRNA stabilization induced by protein kinase C (PKC) down-regulation. In this work, we found that uPA mRNA is rather stable in MDA-MB-231 cells with a half-life of 17 h. We compared the stability of hybrid globin mRNA containing different parts of uPA mRNA in its 3' UTR and found that the A+U-rich sequence of uPA mRNA renders otherwise stable globin mRNA unstable in LLC-PK1 cells but not in MDA-MB-231 cells. We identified a cytoplasmic protein of 40 kDa (p40) which specifically interacts with the A+U-rich sequence. Levels of p40 activity as detected by ultraviolet cross-linking were higher in MDA-MB-231 and PKC-down-regulated LLC-PK1 cells than in untreated LLC-PK1 cells. Prior treatment of the cytoplasm with a specific antibody against heterogeneous nuclear ribonucleoprotein C (hnRNP C) significantly reduced p40 activity. These results suggest a correlation between the A+U-rich sequence-dependent uPA mRNA stabilization in vivo and the binding of hnRNP C to the A+U-rich sequence in vitro.

Animals↗
PubMed1996

Hormonal modulation of c-fos expression in isolated hepatocytes. Effects of angiotensin II and phorbol myristate acetate on transcription and mRNA degradation.

It has been shown that angiotensin II and PMA increase the expression of proto-oncogenes (c-fos, c-myc and c-mos) in liver cells. In this study the effects of angiotensin II and PMA on c-fos transcription and mRNA stability were investigated. Using nuclear run-off transcription assays, it was observed that PMA and angiotensin II induced a rapid increase in c-fos transcription. The transcription rate of the GAPDH gene did not change, indicating that the effects were not general on gene transcription. The ability of these agents to modulate proto-oncogene mRNA stability was tested by measuring c-fos mRNA half-life. It was observed that c-fos mRNA half-life was relatively short (approximately 14-18 min) and that angiotensin II and PMA markedly stabilized mRNA, increasing its half-life (approximately 4-fold and approximately 2-fold, respectively). The protein synthesis inhibitor cycloheximide increased mRNA stability to a much greater extent. Our results clearly demonstrate that angiotensin II and PMA increased c-fos mRNA accumulation in liver cells through two actions: induction of c-fos gene transcription and increase in mRNA stability.

Angiotensin II↗
PubMed2006

Regulation of osmotic stress transcription factor 1 (Ostf1) in tilapia (Oreochromis mossambicus) gill epithelium during salinity stress.

Mechanisms of induction of osmotic stress transcription factor 1 (Ostf1) were analyzed in gill epithelium of tilapia exposed to salinity stress. Experiments with primary cultures of gill epithelial cells revealed that hyperosmotic Ostf1 induction was independent of systemic factors. In addition, the synthetic glucocorticoid receptor agonist dexamethasone did not affect Ostf1 levels, arguing against cortisol being the signal for Ostf1 induction during hyperosmotic stress. Exposure of primary gill cell cultures to a hyperosmotic agent that is cell permeable and non-hypertonic (glycerol) did not trigger Ostf1 induction. However, when gill cells were exposed to hypertonicity (either in the form of NaCl or other forms) Ostf1 was rapidly and significantly induced. Analysis of hnRNA and mRNA levels revealed that Ostf1 upregulation in gill cells of intact fish and primary cultures of gill epithelial cells was mediated by transient mRNA stabilization. In addition to the initial transient mRNA stabilization a subsequent transcriptional induction of Ostf1 was observed. In cultured gill cells increase in Ostf1 mRNA synthesis was stable and very potent, whereas in gill cells of intact fish this increase was transient. This observation suggests positive feedback by Ostf1 or one of its targets and negative feedback by systemic factors on Ostf1 transcription. We conclude that Ostf1 induction in gill epithelial cells of tilapia exposed to salinity stress (1) is independent of cortisol or other systemic factors; (2) depends on hypertonicity as the signal; and (3) is based on transient mRNA stabilization. Moreover, our data on primary cell cultures show that systemic signals are necessary to prevent sustained transcriptional induction of Ostf1 during hyperosmotic stress, indicating feedback regulation and a high degree of complexity of osmosensing and signaling networks in euryhaline fishes.

Animals↗
PubMedDate not supplied

Posttranscriptional regulation of cyclooxygenase-2 in rat intestinal epithelial cells.

Modulation of cyclooxygenase-2 (COX-2) mRNA stability plays an important role in the regulation of its expression by oncogenic Ras. Here, we evaluate COX-2 mRNA stability in response to treatment with two known endogenous promoters of gastrointestinal cancer, the bile acid (chenodeoxycholate; CD) and ceramide. Treatment with CD and ceramide resulted in a 10-fold increase in the level of COX-2 protein and a four-fold lengthening of the half-life of COX-2 mRNA. COX-2 mRNA stability was assessed by Northern blot analysis and by evaluating the AU-rich element located in the COX-2 3'-UTR. A known inhibitor of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK), PD98059, reversed the effects of CD or ceramide to stabilize COX-2 mRNA. Overexpression of a dominant-negative ERK-1 or ERK-2 protein also led to destabilization of COX-2 mRNA. Treatment with a p38 MAPK inhibitor, PD169316, or transfection with a dominant-negative p38 MAPK construct reversed the effect of CD or ceramide to stabilize COX-2 mRNA. Expression of a dominant-negative c-Jun N-terminal kinase (JNK) had no effect on COX-2 mRNA stability in cells treated with CD or ceramide. We conclude that posttranscriptional mechanisms play an important role in the regulation of COX-2 expression during carcinogenesis.

Animals↗
PubMed1977

Stabilization of mRNA following serum-induction of quiescent 3T3 cells.

The stability of mRNA has been measured in 3T3 cells in the resting and the growing states, and also during the transition from the resting to the growing state. Pulse labled poly (A)+ mRNA chased with uridine and cytidine supplemented growth medium decayed with a half-life of 6.5 hr in the resting state, 26 hr during the transition from the resting to the growing condition, and 18 hr during serum-stimulated growth. The half-life of poly(A)+ mRNA determined by steady state labeling yielded similar results in resting and serum-stimulated 3T3 cells. Thus during the transition from resting to serum-stimulated growth in 3T3 cells poly(A)+ mRNA becomes more stable.

Blood↗
PubMed1990

High concentrations of estrogen stabilize vitellogenin mRNA against cytoplasmic degradation but physiological concentrations do not.

Using DNA excess filter hybridization to pulse-labeled cellular RNA, we examined the stability of vitellogenin mRNA in Xenopus liver in relation to estrogen concentration. We showed that pharmacological concentrations of estrogen stabilize vitellogenin mRNA against degradation but that physiological concentrations do not. We concluded that there is little foundation for the common belief that estrogen stabilizes vitellogenin mRNA in normal liver cells and that such stabilization contributes to the normal expression of vitellogenin genes. We also discuss the importance of steroid concentration in other contexts, and show that the widespread tendency to use artificially high concentrations may lead to questionable conclusions.

Animals↗
PubMed1993

Differential glucocorticoid regulation of the pulmonary hydrophobic surfactant proteins SP-B and SP-C.

Glucocorticoids increase expression of the genes for the pulmonary surfactant-associated proteins SP-B and SP-C in fetal lung both in vivo and in vitro. To examine the mechanism of these effects, we studied induction of SP-B and SP-C mRNAs in human fetal lung cultured as explants. Both mRNA levels rose rapidly in response to 100 nM dexamethasone (Dex), with a faster response for SP-B: maximal levels of induction were achieved in < or = 12 h for SP-B (3.5-fold versus control) versus approximately 24 h for SP-C mRNA (35-fold versus control). Cycloheximide (2.5 micrograms/ml) did not affect glucocorticoid induction of SP-B mRNA but markedly decreased induction of SP-C mRNA. In control cultures, cycloheximide did not significantly reduce levels of either transcript. In nuclear run-on assays, Dex increased the rate of gene transcription for both SP-B (2.8 +/- 0.3-fold versus control, n = 4) and SP-C (10- to 30-fold). Using actinomycin D to assess mRNA stability, the t1/2 of SP-B mRNA was increased from 7.5 +/- 0.4 h to 18.8 +/- 2.9 h by Dex treatment (P < 0.05), whereas the t1/2 of SP-C mRNA was not affected (9.3 +/- 1.7 h versus 8.1 +/- 1.2 h; NS). A similar increase in SP-B mRNA t1/2 with Dex (from 6 h to 19 h) was observed in label-chase studies with [3H]uridine. We conclude that glucocorticoids regulate the hydrophobic surfactant proteins of alveolar type II cells by different mechanisms: induction of SP-B is a primary response and includes an increase in both transcription rate and mRNA stability, whereas induction of SP-C is a secondary process, requiring ongoing protein synthesis, involving increased transcription rate without a change in mRNA stability.

Culture Techniques↗
PubMed1996

Regulation of angiotensin II type 2 receptor gene by the protein kinase C-calcium pathway.

In the present study, rat angiotensin II type 2 (AT2) receptor expression was upregulated in confluence-arrested PC12 cells compared with expression in proliferating cells. Treatment with cycloheximide inhibited the increase in mRNA levels in confluent cells. The state of growth arrest by serum deprivation was associated with increased expression of the AT2 receptor, which was markedly suppressed by exposure to the active phorbol ester 12-O-tetradecanoylphorbol 13-acetate and the calcium ionophore A23187. Similar inhibitions were also observed in myocytes isolated from neonatal rat heart. The change in AT2 mRNA levels by serum deprivation was due to the increase in the gene transcription rate. The effect of 12-O-tetradecanoylphorbol 13-acetate was mediated through decreases in gene transcription and mRNA stability, whereas A23187 affected mRNA stability. Vasoactive substances with the protein kinase C-calcium pathway, such as norepinephrine and angiotensin II, also downregulated the AT2 mRNA level in myocytes. These findings indicate that the expression of AT2 receptor in PC12 cells is regulated in a growth state-dependent manner, which is involved in confluence-induced new protein synthesis, thus providing a means by which cells can modulate their responsiveness to external angiotensin II stimulus. The activation of protein kinase C or calcium mobilization modifies this regulatory mechanism, suggesting that neurotransmitters or vasoactive substances with the protein kinase C-calcium pathway at least in part affect neuronal activity or blood pressure control by downregulating AT2 receptor expression.

Animals↗
PubMed2002

Extracellular signal-regulated kinase mediates granulocyte-macrophage colony-stimulating factor messenger RNA stabilization in tumor necrosis factor-alpha plus fibronectin-activated peripheral blood eosinophils.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is critical for promoting the long-term survival of lung- or airway-based eosinophils. Previously, we have shown that fibronectin and tumor necrosis factor alpha induced autocrine production of GM-CSF that markedly enhanced eosinophil survival. Cytokine release was preceded by and dependent on messenger RNA (mRNA) stabilization. Here, we show that mitogen-activated protein kinase (MAPK) activation is responsible for GM-CSF mRNA stabilization in peripheral blood eosinophils (pbeos). Activation of extracellular signal-regulated kinase (ERK) but not p38 correlated with GM-CSF mRNA stability. Although ERK inhibition completely prevented GM-CSF mRNA stabilization, p38 inhibition had a partial effect. To establish which MAPK was crucial, we transduced pbeos with dominant-active TatMEK1(E) or TatMKK3b(E) proteins that selectively phosphorylate ERK or p38, respectively. These studies showed that ERK but not p38 was sufficient for GM-CSF mRNA stabilization. These data are in contradistinction to the c-Jun NH(2)-terminal kinase-mediated regulation of interleukin 2 and 3 mRNAs and suggest unique regulatory features for GM-CSF mRNA in eosinophils.

Asthma↗
PubMed2003

Xenopus cold-inducible RNA-binding protein 2 interacts with ElrA, the Xenopus homolog of HuR, and inhibits deadenylation of specific mRNAs.

Xenopus cold-inducible RNA-binding protein 2 (xCIRP2) is a major cytoplasmic RNA-binding protein in oocytes. In this study, we identify another RNA-binding protein ElrA, the Xenopus homolog of HuR, as an interacting protein of xCIRP2 by yeast two-hybrid screening. As ElrA stabilizes the RNA body in the in vitro mRNA stability system, we examine the role of xCIRP2 in the stabilization of mRNA and find that xCIRP2 inhibits deadenylation of AU-rich element-containing mRNA. These results suggest that xCIRP2 and ElrA may be involved in the regulation of mRNA stability at different steps. By immunoprecipitation with anti-xCIRP2 antibody, we find that xCIRP2 interacts with several mRNAs including mRNA encoding the centrosomal kinase Nek2B in oocytes. xCIRP2 also inhibits deadenylation of the mRNA substrate containing the 3'-untranslated region of Nek2B mRNA in the in vitro system. Our results suggest that xCIRP2 associates with specific mRNAs and can regulate the length of poly(A) tail in Xenopus oocytes.

3' Untranslated Regions↗
PubMed1998

The human analog of murine cystein rich protein 61 [correction of 16] is a 1alpha,25-dihydroxyvitamin D3 responsive immediate early gene in human fetal osteoblasts: regulation by cytokines, growth factors, and serum.

1Alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3) is a potent mediator of differentiation and maintenance of specific functions of osteoblasts. To detect novel targets for 1,25-(OH)2D3 action, we applied differential display PCR to human fetal osteoblast-like cells and identified the human analog of murine cystein rich protein 61 (hCYR61) as a 1,25-(OH)2D3-responsive immediate early gene in differentiated fetal osteoblast-like cells. The murine gene CYR61 is important for cell-cell and cell-matrix interactions, and it belongs to an emerging gene family of cysteine-rich proteins. hCYR61 messenger RNA (mRNA) steady-state levels were stimulated 11-fold by 10 nM 1,25-(OH)2D3 by 1 h and declined to control levels by 4 h. This transient stimulation of hCYR61 mRNA was not inhibited by cycloheximide but was prevented by actinomycin D, indicating that the 1,25-(OH)2D3 effect involves transcriptional events and does not require de novo protein synthesis. hCYR61 mRNA stability was not influenced by 1,25(OH)2D3, whereas cycloheximide treatment stabilized hCYR61 mRNA. FCS, as well as growth factors and cytokines such as basic fibroblast growth factor, epidermal growth factor, tumor necrosis factor alpha, and interleukin-1, strongly elevated hCYR61 mRNA steady-state levels within 1 h. hCYR61 mRNA was expressed also in primary human osteoblasts and osteosarcoma cell lines. Using a commercial tissue blot, hCYR61 mRNA was only observed in skeletal muscle. The fast and transient response of hCYR 61 to 1,25-(OH)2D3, serum, growth factors, and cytokines suggests an important role of hCYR61 for osteoblast function and differentiation.

Animals↗
PubMed1994

Increased transcription and coordinate stabilization of mRNAs for secreted immunoglobulin alpha heavy chain and kappa light chain following stimulation of immunoglobulin A expressing B cells.

Immunoglobulin A (IgA) plays a key role in host protection at mucosal surfaces, yet little is known regarding the molecular mechanisms that govern the expression of this isotype. The studies herein investigated mechanisms that control IgA secretion in response to stimulation with interleukin-4 and interleukin-5, cytokines which are known to regulate IgA responses, and to bacterial lipopolysaccharide. Two mechanisms were shown to govern agonist induced IgA expression in a murine IgA expressing B cell line. In the initial period after stimulation, increased mRNA levels for the secreted form of alpha heavy chain (alpha s), and kappa light chain were paralleled by a transient increase in transcription rates of the corresponding genes. However, with prolonged agonist stimulation, gene transcription rates decreased to near control levels, and increased mRNA levels were associated with a coordinate increase in alpha s and kappa mRNA stability. In striking contrast, these agonists did not affect levels or stability of mRNA for the membrane form of alpha heavy chain (alpha m). Alpha s mRNAs contained multiple poly(A) addition sites located 13-32 nucleotides downstream of a single AAUAAA sequence. Nonetheless, the differential usage of these sites as a mechanism for controlling alpha s mRNA stability could be excluded, since the relative abundance of these different alpha s mRNAs did not differ significantly after agonist stimulation. These data, taken together, suggest that sequences within 107 nucleotides of the 3' end of alpha s mRNA, which are absent in alpha M mRNA, are required for the regulation of alpha s mRNA stability, possibly by acting as targets for regulated trans-acting cellular factors.

Animals↗