Tailored Medication Adherence Incentives Using mHealth for Children With High-Risk Asthma (TAICAM): Protocol for a Randomized Controlled Trial

Background

Poor adherence to inhaled corticosteroid medications for children with high-risk asthma is both well documented and poorly understood. It has a disproportionate prevalence and impact on children of minority demographics in urban settings. Financial incentives have been shown to be a compelling method to engage those in a high-risk asthma population, but whether adherence can be maintained by offering financial incentives and how these incentives can be used to sustain high adherence are unknown.

Objective

The aim of this study is to determine the marginal effects of a financial incentive–based intervention on inhaled corticosteroid adherence, health care system use, and costs.

Methods

Participants include children aged 5 to 12 years who have had either at least two hospitalizations or one hospitalization and one emergency department visit for asthma in the year prior to their enrollment (and their caregivers). Participants are given an electronic inhaler sensor in order to track their medication use over a period of 7 months. After a 1-month period of observation, participants are randomized to 1 of 3 arms for a 3-month period. Participants in arm 1 receive daily text message reminders, feedback, and gain–framed, nominal financial incentives; participants in arm 2 receive daily text message reminders and feedback only, and participants in arm 3 receive no reminders, feedback, or incentives. All participants are subsequently observed for an additional 3-month period with no reminders, feedback, or incentives to assess whether any sustained effects are apparent.

Results

Study enrollment began in September 2019 with a target sample size of N=125 children. As of June 2020, 61 children have been enrolled. Data collection is estimated to be completed in June 2022, and analyses will be completed by June 2023.

Conclusions

This study will provide data that will help to determine whether a financial incentive–based mobile health intervention for promoting inhaled corticosteroid use can be effective in patients with high-risk asthma over longer periods.

Trial Registration

Clinicaltrial.gov NCT03907410; https://clinicaltrials.gov/ct2/show/NCT03907410

International Registered Report Identifier (IRRID)

DERR1-10.2196/16711

Inhibition of ANKRD1 sensitizes human ovarian cancer cells to endoplasmic reticulum stress-induced apoptosis

High expression of Ankyrin Repeat Domain 1 (ANKRD1) in ovarian carcinoma is associated with poor survival, and in ovarian cancer cell lines is associated with platinum resistance. Importantly, decreasing ANKRD1 expression using siRNA increases cisplatin sensitivity. In this study, we investigated possible mechanisms underlying the association of ANKRD1 with cisplatin response. We first demonstrated that cisplatin-induced apoptosis in ovarian cancer cell lines was associated with endoplasmic reticulum (ER) stress, evidenced by induction of Glucose-Regulated Protein 78 (GRP78), growth arrest- and DNA damage-inducible gene 153 (GADD153) and increased intracellular Ca(2+) release. The level of sensitivity to cisplatin-induced apoptosis was associated with ANKRD1 protein levels and poly (ADP-ribose) polymerase (PARP) cleavage. COLO 316 ovarian cancer cells, which express high ANKRD1 levels, were relatively resistant to cisplatin, and ER stress-induced apoptosis, whereas OAW42 and PEO14 cells, which express lower ANKRD1 levels, are more sensitive to ER stress-induced apoptosis. Furthermore, we show that overexpression of ANKRD1 attenuated cisplatin-induced cytotoxicity, and conversely siRNA knockdown of ANKRD1 sensitized ovarian cancer cells to cisplatin and ER stress-induced apoptosis associated with induction of GADD153, and downregulation of BCL2 and BCL-XL. Taken together, these results suggest that ANKRD1 has a significant role in the regulation of apoptosis in human ovarian cancer cells, and is a potential molecular target to enhance sensitivity of ovarian cancer to chemotherapy.

A high-throughput screening assay for the identification of flavivirus NS5 capping enzyme GTP-binding inhibitors: implications for antiviral drug development

There are no effective antivirals currently available for the treatment of flavivirus infection in humans. As such, the identification and characterization of novel drug target sites are critical to developing new classes of antiviral drugs. The flavivirus NS5 N-terminal capping enzyme (CE) is vital for the formation of the viral RNA cap structure, which directs viral polyprotein translation and stabilizes the 5' end of the viral genome. The structure of the flavivirus CE has been solved, and a detailed understanding of the CE-guanosine triphosphate (GTP) and CE-RNA cap interactions is available. Because of the essential nature of the interaction for viral replication, disrupting CE-GTP binding is an attractive approach for drug development. The authors have previously developed a robust assay for monitoring CE-GTP binding in real time. They adapted this assay for high-throughput screening and performed a pilot screen of 46 323 commercially available compounds. A number of small-molecule inhibitors capable of displacing a fluorescently labeled GTP in vitro were identified, and a second functional assay was developed to identify false positives. The results presented indicate that the flavivirus CE cap-binding site is a valuable new target site for antiviral drug discovery and should be further exploited for broad-spectrum anti-flaviviral drug development.

Infectious alphavirus production from a simple plasmid transfection+

We have developed a new method for producing infectious double subgenomic alphaviruses from plasmids transfected into mammalian cells. A double subgenomic Sindbis virus (TE3'2J) was transcribed from a cytomegalovirus PolII promoter, which results in the production of infectious virus. Transfection of as little as 125 ng of plasmid is able to produce 1 × 10⁸ plaque forming units/ml (PFU/ml) of infectious virus 48 hours post-transfection. This system represents a more efficient method for producing recombinant Sindbis viruses.

Genetic, functional, and histopathological evaluation of two C-terminal BRCA1 missense variants

BACKGROUND

The vast majority of BRCA1 missense sequence variants remain uncharacterized for their possible effect on protein expression and function, and therefore are unclassified in terms of their pathogenicity. BRCA1 plays diverse cellular roles and it is unlikely that any single functional assay will accurately reflect the total cellular implications of missense mutations in this gene.

OBJECTIVE

To elucidate the effect of two BRCA1 variants, 5236G>C (G1706A) and 5242C>A (A1708E) on BRCA1 function, and to survey the relative usefulness of several assays to direct the characterisation of other unclassified variants in BRCA genes.

METHODS AND RESULTS

Data from a range of bioinformatic, genetic, and histopathological analyses, and in vitro functional assays indicated that the 1708E variant was associated with the disruption of different cellular functions of BRCA1. In transient transfection experiments in T47D and 293T cells, the 1708E product was mislocalised to the cytoplasm and induced centrosome amplification in 293T cells. The 1708E variant also failed to transactivate transcription of reporter constructs in mammalian transcriptional transactivation assays. In contrast, the 1706A variant displayed a phenotype comparable to wildtype BRCA1 in these assays. Consistent with functional data, tumours from 1708E carriers showed typical BRCA1 pathology, while tumour material from 1706A carriers displayed few histopathological features associated with BRCA1 related tumours.

CONCLUSIONS

A comprehensive range of genetic, bioinformatic, and functional analyses have been combined for the characterisation of BRCA1 unclassified sequence variants. Consistent with the functional analyses, the combined odds of causality calculated for the 1706A variant after multifactorial likelihood analysis (1:142) indicates a definitive classification of this variant as "benign". In contrast, functional assays of the 1708E variant indicate that it is pathogenic, possibly through subcellular mislocalisation. However, the combined odds of 262:1 in favour of causality of this variant does not meet the minimal ratio of 1000:1 for classification as pathogenic, and A1708E remains formally designated as unclassified. Our findings highlight the importance of comprehensive genetic information, together with detailed functional analysis for the definitive categorisation of unclassified sequence variants. This combination of analyses may have direct application to the characterisation of other unclassified variants in BRCA1 and BRCA2.

Expression levels of heat shock protein 60 in human endothelial cells in vitro are unaffected by exposure to 50 Hz magnetic fields

Magnetic fields (MFs) from domestic power sources have been implicated as being a potential risk to human health. A number of epidemiological studies have found a significant link between exposure to MFs and increased rates of cancers. There have also been a number of in vivo and in vitro studies reporting effects of MFs in animal disease models and on the expression or activity of a range of proteins. In the past decade, our group proposed that atherosclerosis may have an autoimmune component, with heat shock protein 60 (Hsp60) expressed in endothelial cells as the dominant autoantigen. A number of stressors have been shown to induce the expression of Hsp60, including the classical risk factors for atherosclerosis. We were interested to see if the exposure of endothelial cells to an MF elicited increased expression of Hsp60, as has been reported previously for Hsp70. The present work describes the exposure of endothelial cells to domestic power supply (50 Hz) MFs at an intensity of 700 microT. The results from our system indicate that cultured endothelial cells exposed to a high intensity of MF either alone or in combination with classical heat stress show no effects on the expression of Hsp60 at either the messenger ribonucleic acid or the protein level. As such, there is no evidence that exposure to extremely low-frequency MF would be expected to increase the expression of Hsp60 and therefore the initiation or progression of atherosclerosis.

ARM domain-dependent nuclear import of adenomatous polyposis coli protein is stimulated by the B56 alpha subunit of protein phosphatase 2A

Inactivating mutations in the adenomatous polyposis coli (APC) gene correlate with progression of colon cancer and familial adenomatous polyposis. The APC tumor suppressor contributes to chromosome segregation and turnover of the oncogenic transcriptional activator beta-catenin, and these activities are impaired by truncating cancer mutations. APC was recently identified as a shuttling protein whose subcellular distribution is regulated by two nuclear localization signals (NLSs) and multiple nuclear export signals (NESs). Here, we show that mutant disease-linked truncated forms of APC, most of which lack the two central NLSs and certain NES sequences, retain nuclear-cytoplasmic shuttling activity. Nuclear export of truncated APC is mediated by a dominant N-terminal NES. Nuclear import of NLS-deficient APC mutants is facilitated by the N-terminal ARM domain. Furthermore, co-expression of the ARM-binding protein, B56 alpha, increased the nuclear localization of mutant and wild-type APC. The minimal B56 alpha-responsive sequence mapped to APC amino acids 302-625. B56 alpha is a regulatory subunit of protein phosphatase 2A; however, its ability to shift APC to the nucleus was independent of phosphatase activity. We conclude that APC nuclear import is regulated by the ARM domain through its interaction with B56 alpha and postulate that APC/B56 alpha complexes target the dephosphorylation of specific proteins within the nucleus.

Nuclear export of human beta-catenin can occur independent of CRM1 and the adenomatous polyposis coli tumor suppressor

beta-Catenin is a mediator of the Wnt-signaling pathway. In many cancers, beta-catenin is stabilized and accumulates in the nucleus where it associates with lymphoid-enhancing factor 1/ T-cell transcription factors to activate genes involved in cell transformation. Previously, we showed that adenomatous polyposis coli (APC) protein can regulate beta-catenin localization by nuclear export. In this study, we used in vitro transport assays to test whether cellular beta-catenin can exit the nucleus independent of APC and the CRM1 export receptor. In digitonin-permeabilized SW480 (APC(mut/mut)) tumor cells, nuclear beta-catenin decreased >60% in export reactions in the absence of exogenous factors. Under similar conditions, nuclear c-ABL was only exported after the addition of cytosolic extract, and the export was blocked by the CRM1-specific inhibitor, leptomycin B. The nuclear export of beta-catenin was not blocked by leptomycin B treatment, revealing a CRM1- and APC-independent pathway. The export of beta-catenin was sensitive to lower temperatures and the removal of ATP, indicating an active process. Ectopically expressed yellow fluorescent protein-beta-catenin also displayed CRM1-independent export. Conversely, the overexpression of the CRM1 transporter moderately stimulated export of nuclear beta-catenin, confirming that beta-catenin exits the nucleus by at least two distinct pathways. The shuttling ability of tumor cell beta-catenin has implications for its regulation and its role in transferring signals between the nucleus and plasma membrane.

Identification of a functional nuclear export sequence in BRCA1

Germ-line mutations in the tumor suppressor gene Brca1 confer increased susceptibility to breast and ovarian cancers. BRCA1 is a 1863-amino acid protein with roles in transcriptional regulation and the cellular responses to DNA damage. Given its function in these nuclear processes, the subcellular localization of BRCA1 is an important issue and has been the object of recent controversy. BRCA1 contains two nuclear localization signals and is most frequently detected in the cell nucleus by immunofluorescence microscopy. In this study, we show that BRCA1 is a nuclear-cytoplasmic shuttling protein, capable of both entering and exiting the nucleus. We identified a functional Rev-type nuclear export sequence ((81)QLVEELLKIICAFQLDTGL) near the amino terminus of BRCA1 that facilitates export via the CRM1/exportin pathway. Mutational inactivation of this nuclear export sequence, or treatment of cells with the CRM1-specific export inhibitor leptomycin B, induced nuclear accumulation of ectopic full-length BRCA1. Moreover, overexpression of the CRM1 export receptor resulted in decreased nuclear localization of endogenous BRCA1. The unexpected ability of BRCA1 to shuttle between nucleus and cytoplasm may have implications for the regulation and function of this tumor suppressor.

Nuclear-cytoplasmic shuttling of APC regulates beta-catenin subcellular localization and turnover

Mutational inactivation of the APC gene is a key early event in the development of familial adenomatous polyposis and colon cancer. APC suppresses tumour progression by promoting degradation of the oncogenic transcriptional activator beta-catenin. APC gene mutations can lead to abnormally high levels of beta-catenin in the nucleus, and the consequent activation of transforming genes. Here, we show that APC is a nuclear-cytoplasmic shuttling protein, and that it can function as a beta-catenin chaperone. APC contains two active nuclear export sequences (NES) at the amino terminus, and mutagenesis of these conserved motifs blocks nuclear export dependent on the CRM1 export receptor. Treatment of cells with the CRM1-specific export inhibitor leptomycin B shifts APC from cytoplasm to nucleus. beta-catenin localization is also regulated by CRM1, but in an APC-dependent manner. Transient expression of wild-type APC in SW480 (APCmut/mut) colon cancer cells enhances nuclear export and degradation of beta-catenin, and these effects can be blocked by mutagenesis of the APC NES. These findings suggest that wild-type APC controls the nuclear accumulation of beta-catenin by a combination of nuclear export and cytoplasmic degradation.

A comparison of the activity, sequence specificity, and CRM1-dependence of different nuclear export signals

Nuclear export sequences (NESs) have been identified in many cellular proteins, but it remains unclear how different NESs compare in activity. We describe a sensitive new in vivo export assay which we have used to assess the relative export activity of different types of NES. The most common type of export sequence resembles that first identified in the HIV-1 Rev protein and typically comprises a core of large hydrophobic amino acids that specify recognition by the CRM1 export receptor. We compared 10 previously identified Rev-type NESs in our assay, and whereas all were functional, the relative export activities of these signals varied considerably. We further identified 3 new Rev-type NESs from a computer database search, and each export signal was assigned a score of 1 to 9 and ranked in order of activity (e.g., PKI > c-ABL > Ran-BP1 > FMRP > PML > IkappaB-alpha > hdm2). The weakest NESs were found in the p53 tumor suppressor and the p53-regulated proteins p21 and hdm2, which are all normally localized to the nucleus. All of the Rev-type NESs were inactivated by mutation of key hydrophobic residues and by treatment with the CRM1-specific export inhibitor, leptomycin B. In contrast, a different type of export signal, the KNS shuttling element derived from hnRNP K, exhibited a modest export activity that was insensitive to leptomycin B treatment. KNS thus appears to mediate export via a CRM1-independent pathway. Mutagenesis of the KNS sequence identified, for the first time, specific serines and acidic residues necessary for its export activity, thereby distinguishing KNS from other types of nuclear transport signal. We have shown that different nuclear export signals can vary profoundly in activity and therefore conclude that the nuclear export rate of a specific shuttling protein largely depends on both the strength and the accessibility of its NES.

Translational regulation of mRNAs with distinct IRE sequences by iron regulatory proteins 1 and 2

Iron regulatory proteins 1 and 2 (IRP-1, IRP-2) interact with iron-responsive elements (IREs) present in the 5'- or 3'-untranslated regions (UTR) of several mRNAs coding for proteins in iron metabolism. Whereas binding of IRP-1 and -2 to an IRE in the 5'-UTR inhibits mRNA translation in vitro, it has remained unknown whether either endogenous protein is sufficient to control translation in mammalian cells. We analyzed this question by taking advantage of published mutant IREs that are exclusively recognized by either IRP-1 or IRP-2 in vitro. These IREs were inserted into the 5'-UTR of a human growth hormone reporter mRNA, and translational regulation was measured in stably transfected mouse L cells. Cells cultured in iron-rich or -depleted medium were labeled with [35S]methionine, and secreted growth hormone was immunoprecipitated. IREs with loop sequence specific for IRP-1 (UAGUAC), IRP-2 (CCGAGC), or both proteins (GAGUCG and the wild-type CAGUGC sequence) all mediated translational regulation, in contrast to a control sequence (GCUCCG) that binds neither IRP-1 nor IRP-2. Control experiments excluded IRP-1 binding to the IRP-2-specific sequence in vivo. The present data demonstrate that IRP-1 and IRP-2 can independently function as translational repressors in living cells.

Interactions between HIV Rev and nuclear import and export factors: the Rev nuclear localisation signal mediates specific binding to human importin-beta

The human immunodeficiency virus type 1 (HIV-1) Rev protein binds to unspliced HIV-1 pre-mRNA and exports it from the nucleus. Rev itself can "shuttle" between the nucleus and cytoplasm. This bi-directional transport is mediated by two specific Rev sequences: a nuclear localisation signal (NLS), which overlaps the RNA-binding domain, and a distinct nuclear export signal (NES). In this study we characterised new monoclonal antibodies that bind different epitopes of Rev, including the import and export sequences. In RNA bandshift assays, we observed that formation of a multimeric complex between Rev and its target RNA completely masks the Rev NLS, whereas the NES remains readily accessible. We then tested for signal-mediated interactions between Rev and different nuclear transport receptors, using mutations in the Rev NES or NLS to control for specificity. Extensive biochemical analyses did not reveal any direct NES-dependent interaction between Rev (free or RNA-bound) and the previously proposed export co-factors, human RIP/Rab and eIF-5A. By contrast, similar tests showed that Rev binds directly via its arginine-rich NLS to the human nuclear import receptor, importin-beta. This interaction was highly specific and was abolished by mutation in the Rev NLS. Importin-beta did not bind to the RNA-bound form of Rev, providing a mechanism to ensure that Rev is imported only following release of its RNA cargo. Unlike many NLS-containing proteins that bind stably to an importin-alpha/beta heterodimer, the binding of Rev to importin-beta was actually blocked by importin-alpha receptor. Our findings suggest that Rev and importin-alpha bind (via an arginine-rich sequence) to a similar region on importin-beta. In addition, we show that the complex between Rev and importin-beta can be dissociated by the nuclear Ran GTPase, but only when Ran is in the GTP-bound form. The series of interactions we describe provide a novel pathway for the import of Rev across the nuclear pore complex, and a mechanism for its release into the nucleoplasm.

The management of unilateral lateral mass/facet fractures of the subaxial cervical spine: the use of magnetic resonance imaging to predict instability

STUDY DESIGN

Retrospective review of the clinical course and cervical spine plain radiographs, computed tomography, and magnetic resonance imaging of 24 consecutive patients for a 2-year period with a unilateral lateral mass/facet fracture.

OBJECTIVE

To propose a treatment algorithm for the management of unilateral lateral mass/facet fractures of the subaxial cervical spine based on ligamentous injury detected by magnetic resonance imaging.

SUMMARY OF BACKGROUND DATA

There have been no previous reports of the use of magnetic resonance imaging to predict clinical instability.

METHODS

A retrospective review of the clinical course of all unilateral mass/facet fractures identified over a 2-year period was conducted. All cervical spine plain radiographs, computed tomography scans, and magnetic resonance images were reviewed by a neuroradiologist blinded to the clinical course of the patient. Magnetic resonance T1-weighted and inversion recovery images were used to evaluate the integrity of the facet region, interspinous ligament, anterior longitudinal ligament, and posterior longitudinal ligament.

RESULTS

Twenty-four unilateral lateral mass/facet fractures were identified. Only six initial cervical spine series demonstrated a bony abnormality at the level of the fracture. The fractures were identified by computed tomography and were almost all nondisplaced or minimally displaced. Less than half of the fractures extended ventrally to involve the transverse process or foramen transversarium or dorsally to involve the lamina. Twelve fractures were nonoperatively treated and 12 were treated surgically for stabilization. Ten patients in the operative group presented with or developed a subluxation. Nine of these patients had injury to at least three of the four ligaments evaluated by magnetic resonance imaging. In the nonoperative group, only three patients had extensive ligamentous injury at the level of the fracture. All three of these patients were lost to follow-up.

CONCLUSIONS

Plain radiographs of the cervical spine lack sensitivity to detect the presence of lateral mass/ facet fractures. The appearance of the fracture on computed tomography does not indicate instability. The degree of ligamentous injury at the level of the fracture demonstrated on magnetic resonance imaging correlates with instability in this series. Operative stabilization may be indicated for unilateral lateral mass fractures that present with a subluxation or that have injury to at least three of the following ligaments: the facet region, the interspinous ligament, the anterior longitudinal ligament, and the posterior longitudinal ligament. However, before a definitive management plan can be formulated, results from this small series require further validation.

Interaction between iron-regulatory proteins and their RNA target sequences, iron-responsive elements

In this chapter, we have focused on the biochemistry of IRP-1 and the features which distinguish it from the related RNA-binding protein, IRP-2. IRP-1 is the cytoplasmic isoform of the enzyme aconitase, and, depending on iron status, may switch between enzymatic and RNA-binding activities. IRP-1 and IRP-2 are trans-acting regulators of mRNAs involved in iron uptake, storage and utilisation. The finding of an IRE in the citric acid cycle enzymes, mitochondrial aconitase and succinate dehydrogenase, suggests that the IRPs may also influence cellular energy production. These two proteins appear to bind RNAs with different but overlapping specificity, suggesting that they may regulate the stability or translation of as yet undefined mRNA targets, possibly extending their regulatory function beyond that of iron homeostasis. The interaction between the IRPs and the IRE represents one of the best characterised model systems for posttranscriptional gene control, and given that each IRP can also recognise its own unique set of RNAs, the search for new in vivo mRNA targets is expected to provide yet more surprises and insights into the fate of cytoplasmic mRNAs.

Iron regulatory proteins 1 and 2

Iron uptake and storage in mammalian cells is at least partly regulated at a post-transcriptional level by the iron regulatory proteins (IRP-1 and IRP-2). These cytoplasmic regulators share 79% similarity in protein sequence and bind tightly to conserved mRNA stem-loops, named iron-responsive elements (IREs). The IRP:IRE interaction underlies the regulation of translation and stability of several mRNAs central to iron metabolism. The question of why the cell requires two such closely related regulatory proteins may be resolved as we learn more about the expression and regulation of these proteins. It is evident so far that, despite similarities, the IRPs differ in several important respects. They are coordinately regulated by cellular iron, but whereas IRP-1 is inactivated by high iron levels, IRP-2 is rapidly degraded. Further differences arise in their expression and RNA-binding specificity. The two proteins each recognise a large repertoire of IRE-like sequences, including a small group of exclusive RNA targets. These findings hint that IRP-1 and IRP-2 may bind preferentially to certain mRNAs in vivo, possibly extending their known functions beyond the regulation of intracellular iron homeostasis.

Iron regulatory proteins 1 and 2 bind distinct sets of RNA target sequences

Iron regulatory proteins (IRPs) 1 and 2 bind with equally high affinity to iron-responsive element (IRE) RNA stem-loops located in mRNA untranslated regions and, thereby, post-transcriptionally regulate several genes of iron metabolism. In this study we define the RNA-binding specificities of mouse IRP-1 and IRP-2. By screening loop mutations of the ferritin H-chain IRE, we show that both IRPs bind well to a large number of IRE-like sequences. More significantly, each IRP was found to recognize a unique subset of IRE-like targets. These IRP-specific groups of IREs are distinct from one another and are characterized by changes in certain paired (IRP-1) or unpaired (IRP-2) loop nucleotides. We further demonstrate the application of such sequences as unique probes to detect and distinguish IRP-1 from IRP-2 in human cells, and observe that the IRPs are regulated similarly by iron and reducing agents in human and rodent cells. Importantly, the ability of each IRP to recognize an exclusive subset of IREs was conserved between species. These findings suggest that IRP-1 and IRP-2 may each regulate unique mRNA targets in vivo, possibly extending their function beyond the regulation of intracellular iron homeostasis.

Succinate dehydrogenase b mRNA of Drosophila melanogaster has a functional iron-responsive element in its 5'-untranslated region

Iron-responsive elements (IREs) are cis-acting mRNA stem-loop structures that specifically bind cytoplasmic iron regulatory proteins (IRPs). IRP-IRE interactions mediate the coordinate post-transcriptional regulation of key proteins in iron metabolism, such as ferritin, transferrin receptor, and erythroid 5-aminolevulinic acid synthase. Depending on whether the IRE is located in the 5'- or 3'-untranslated region (UTR), binding of IRP will inhibit mRNA translation or degradation, respectively. Here we describe a new IRE in the 5'-UTR of succinate dehydrogenase subunit b (SDHb) mRNA of Drosophila melanogaster. The SDHb IRE binds in vitro to vertebrate and insect IRPs with a high affinity equal to that of human ferritin H chain IRE. Under conditions of iron deprivation, SDHb mRNA of Drosophila SL-2 cells shifts to a non-polysome-bound pool. Moreover, translation of a human growth hormone mRNA with the SDHb IRE in its 5'-UTR is iron-dependent in stably transfected L cells. We conclude that the SDHb IRE mediates translational inhibition both in insect and vertebrate cells. This constitutes the first identification of a functional IRE in insects. Furthermore, Drosophila SDHb represents the second example, after porcine mitochondrial aconitase, of an enzyme of the citric acid cycle whose mRNA possesses all necessary features for translational regulation by cellular iron levels.

Differential modulation of the RNA-binding proteins IRP-1 and IRP-2 in response to iron. IRP-2 inactivation requires translation of another protein

Iron regulatory proteins (IRPs)-1 and -2 bind specific mRNA hairpin structures known as iron-responsive elements and thereby post-transcriptionally regulate proteins involved in iron uptake, storage, and utilization. In this study, we compared modulation of the RNA-binding activities of IRP-1 and IRP-2. We show that in vitro RNA-binding can be inhibited for each IRP by the alkylation of free sulfhydryl groups with N-ethylmaleimide, or by oxidation with diamide. The in vivo iron regulation of IRP-1 and IRP-2 appeared to involve different pathways. Both proteins are activated in Ltk- cells following iron chelation. This induction, however, was distinguishable by the addition of translation inhibitors, which temporarily delayed activation of IRP-1 by up to 8 h, but fully blocked IRP-2 induction for up to 20 h. The activation of IRP-2 was also prevented by transcription inhibition with actinomycin D. Further analysis revealed that, while both IRPs are rapidly inactivated following iron treatment of iron-depleted cells, the repression of IRP-2 was again completely translation dependent. Immunoblot analysis suggests that iron modulation of IRP-1 activity is predominantly a posttranslational process. This contrasts with IRP-2, whose activation reflected the accumulation of stable IRP-2 protein by de novo synthesis. IRP-2 inactivation/degradation occurred upon readdition of iron, but it required translation of another protein. The existence of an independent regulator of IRP-2 may help explain the differential regulation and expression of the two IRP proteins in different tissues and cell lines.

Optimal sequence and structure of iron-responsive elements. Selection of RNA stem-loops with high affinity for iron regulatory factor

Iron regulatory factor (IRF) is a cytoplasmic mRNA-binding protein with specificity for iron-responsive element (IRE) RNA stem-loops. IRF post-transcriptionally regulates intracellular iron levels via binding to IREs in the untranslated regions of ferritin, transferrin receptor, and erythroid 5-aminolevulinic-acid synthase mRNAs. Specific IRE nucleotides are phylogenetically conserved: those of the 6-base loop (5'-CAGUGN-3') and an unpaired "bulge" cytosine. We prepared a pool of 16,384 IRE molecules randomized at these seven nucleotide positions and employed in vitro selection to identify RNAs that bind human IRF. Two major classes of high affinity RNA ligands were selected; the optimal loop sequences of each are 5'-CAGUGN-3' (wild type) and 5'-UAGUAN-3'. This novel finding predicts base pairing within the IRE loop between positions 1 and 5, thus facilitating the formation of a specific loop structure in which nucleotides at positions 2-4 are made accessible for protein interaction. Nucleotide substitution at these loop positions, or at the position of the bulge cytosine, decreased binding by 36-99%. In addition, we demonstrate a preferred IRE bulge structure and report a striking difference in the RNA binding specificity of rat IRF compared with that of the related IRE-binding protein, IRFB.

Mutational analysis of the [4Fe-4S]-cluster converting iron regulatory factor from its RNA-binding form to cytoplasmic aconitase

The control of cellular iron homeostasis involves the coordinate post-transcriptional regulation of ferritin mRNA translation and transferring receptor mRNA stability. These regulatory events are mediated by a soluble cytoplasmic protein, iron regulatory factor (IRF), which binds specifically to mRNA hairpin structures, termed iron-responsive elements (IREs), in the respective mRNAs. IRF is modulated by variations of cellular iron levels and exists as either an apo-protein or a [4Fe-4S]-cluster protein. The two conformations show distinct, mutually exclusive functions. High-affinity IRE binding is observed with the apo-form induced by iron deprivation, but is lost under high iron conditions when IRF is converted to the [4Fe-4S]-cluster form which shows cytoplasmic aconitase activity. Moreover, IRE binding is inactivated by the sulfhydryl-oxidizing agent diamide and fully activated in vitro by 2% 2-mercapto-ethanol, whereas alkylation of IRF inhibits IRE binding. In the present study, we analyzed each of the above features using site-directed mutants of recombinant human IRF. The results support the bifunctional nature of IRF. We conclude that cysteines 437, 503 and 506 anchor the [4Fe-4S]-cluster, and are essential to the aconitase activity. Mutagenesis changing any of the cysteines to serine leads to constitutive RNA binding in 0.02% 2-mercaptoethanol. Cysteine 437 is particularly critical to the RNA-protein interaction. The spontaneous or diamide-induced formation of disulfide bonds between cysteines 437 and 503 or 437 and 506, in apo-IRF, as well as its alkylation by N-ethylmaleimide, inhibit binding to the IRE.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of a second RNA-binding protein in rodents with specificity for iron-responsive elements

Iron regulatory factor (IRF) is a cytoplasmic RNA-binding protein involved in regulating iron homeostasis. IRF controls expression of ferritin and transferrin receptor post-transcriptionally via specific binding to stem-loop iron-responsive elements (IREs) located in the untranslated regions of the respective mRNAs. We have confirmed by RNA band-shift analysis that a second IRE-protein complex observed in different rodent cell extracts is, like IRF, regulated by intracellular iron levels. This faster migrating complex appears to represent a specific interaction between the ferritin IRE and an iron-regulated protein that is distinct from IRF, as concluded from the following lines of evidence. First, UV cross-linking and partial digestion with different proteases revealed different peptide patterns for the two IRE-protein complexes. Second, antiserum raised against IRF peptides immunoprecipitated only authentic IRF and not the protein of the faster migrating complex, as determined by band-shift analysis. Following separation of the two IRE-binding proteins by ion-exchange chromatography, only the IRF-containing fraction reacted with the antibodies on Western blots. The second protein binds IREs with an affinity similar to that of IRF as demonstrated by competition with a ferritin IRE and related stem-loop RNAs. UV cross-linking experiments indicate that this second protein, tentatively named IRFB, has a molecular mass of approximately 105 kDa. Analysis of mouse tissues revealed differences in the distribution of IRF and IRFB. Whereas IRF protein and IRE binding activity were predominant in liver, intestine, and kidney, the IRFB protein(s) revealed highest binding activity in intestine and brain. Our data support the existence of two distinct iron-regulated IRE-binding proteins in rodents.

Expression of the nm23-2/NDP kinase alpha gene in rat mammary and oral carcinoma cells of varying metastatic potential

Reduced expression of the putative metastasis-suppressor gene, nm23-1, has previously been correlated with high tumour metastatic potential. The involvement of the related and proximally-located nm23-2 gene in the suppression of tumour metastasis, however, has not yet been tested. In this study, we compared nm23-2 RNA levels in cell lines derived from three independent rat mammary carcinomas. Northern blot analysis revealed no correlation between nm23-2 RNA levels and metastatic potential in parent or clonal cell lines derived from chemically-induced (MAT 13762, DMBA-8) or spontaneous (BC1) rat mammary carcinomas. Cloning and sequencing of an nm23-2 cDNA from metastatic BC1 cells demonstrated that the predicted coding sequence of nm23-2 RNA in these cells was not inactivated by mutation. Further analysis showed that the nm23-2 gene was not down-regulated in H-ras-transfected metastatic clones or other metastatic cell lines derived from a spontaneous rat paraoral squamous cell carcinoma, B10. The data do not suggest a correlation between nm23-2 gene expression and metastasis-suppression in these tumours.

Dexamethasone decreases urokinase plasminogen activator mRNA stability in MAT 13762 rat mammary carcinoma cells

The glucocorticoid dexamethasone was observed to decrease urokinase plasminogen activator (uPA) RNA levels from within 1 h of treatment of MAT 13762 mammary adenocarcinoma cells. The drug did not alter the rate of uPA gene transcription in these cells, but decreased the stability of cytoplasmic uPA mRNA transcripts. Results from cycloheximide and actinomycin D experiments indicated that the dexamethasone-mediated reduction in uPA RNA required both new protein and RNA synthesis. Based on these results, we propose that dexamethasone induces a short-lived protein(s) which down-regulates uPA RNA levels post-transcriptionally in these metastatic tumour cells.

TATA box-independent transcription of the human tissue plasminogen activator gene initiates within a sequence conserved in related genes

Transcription of the human tissue-type plasminogen activator (tPA) gene has been reported to initiate from a single site proximal to a TATA box motif [1985, J. Biol. Chem. 260, 11223-11230]. In this study, we utilized primer extension analysis to evaluate the tPA mRNA start site in phorbol-12-myristate 13-acetate (PMA) induced WI-38 human lung fibroblast cells. Whilst some tPA mRNA initiated from the predicted TATA-proximal location (+1), a 10-fold greater proportion of tPA mRNA transcripts initiated 110 bases downstream from a sequence conserved and utilized as the TATA-independent transcription start site in the rodent tPA genes. Moreover, the transfection and expression in different cell types of a cosmid containing the entire human tPA gene resulted in utilization of the same downstream (+110) start site. We propose that this, rather than the previously published position, is the major transcriptional initiation point for the human tPA gene. A core sequence (5'-CAGAGCTG-3') was identified which is common to the TATA-independent mRNA start sites of the human, mouse and rat tPA genes, and which demonstrates only partial similarity to sequences found at the initiation point of other TATA-independent genes.

Transcriptional and posttranscriptional activation of urokinase plasminogen activator gene expression in metastatic tumor cells

Urokinase plasminogen activator (uPA) is a serine protease which has frequently been implicated in the process of tumor cell invasion and metastasis. The degree of expression and mode(s) of regulation of the uPA gene in metastatic compared with nonmetastatic tumor cells have not yet been addressed. We have cloned and sequenced a full-length rat uPA complementary DNA and utilized Northern blot analysis to report that the uPA gene is expressed at levels 3.5- to 70-fold higher in metastatic cell lines than in nonmetastatic cell lines derived from two independent rat mammary adenocarcinomas. Nuclear run-on assays and RNA half-life estimations indicated that metastatic MAT 13762 rat mammary adenocarcinoma cells expressed 3.5-fold higher levels of uPA RNA than a nonmetastatic derivative (J-clone), due to a combined increase in uPA gene transcription and cytoplasmic RNA stability. By contrast, uPA RNA (and enzyme) levels were elevated by up to 70-fold in metastatic clones of dimethylbenz(a)anthracene-induced rat mammary adenocarcinoma (DMBA-8) due to predominantly posttranscriptional mechanisms. Moreover, treatment of nonmetastatic DMBA-8 cell lines with protein synthesis inhibitors led to an increase in nuclear and cytoplasmic uPA RNA levels, without altering the rate of uPA gene transcription. These results suggest that in addition to gene transcription, posttranscriptional events localized in the nucleus and cytoplasm are key determinants of uPA gene activation in rat mammary adenocarcinomas.

Post-transcriptional regulation of urokinase plasminogen activator gene expression occurs in the nucleus of BC1 rat mammary tumor cells

The regulation of urokinase plasminogen activator (uPA) expression was investigated in 2 highly metastatic rat mammary adenocarcinoma cell lines, BC1 and MAT 13762. BC1 cells were observed to synthesize, on average, 10 times less uPA enzyme and mRNA than MAT 13762 cells; however this difference was not accounted for by differences in uPA gene copy number/structure or in the rate of uPA gene transcription in the cell lines studied. Moreover, Northern blot analysis of invasive sub-populations derived in vitro from the BC1 cell line revealed levels of uPA expression similar to those of the parent, but a 3-fold elevation in expression of the metalloprotease gene, transin. Further investigation showed that treatment of BC1 cells with either of the protein synthesis inhibitors, cycloheximide or anisomycin, increased the level of both nuclear and cytoplasmic uPA RNA 6- to 18-fold in 4 hr, whilst inducing a maximum 2.6-fold increase in the rate of uPA gene transcription. This increase in uPA gene expression may therefore reflect, in part, an increase in the stability and/or processing of nuclear uPA transcripts. These results suggest that the degree of uPA gene expression does not correlate directly with BC1 tumor-cell invasion in vitro, and that the uPA gene is down-regulated, at least in part, post-transcriptionally in the nucleus of BC1 mammary tumor cells.

Subfamilies of serine tRNA genes in the bovine genome

A bovine tRNA gene cluster has been characterized and the sequences of four tDNAs determined. Two of the tDNAs could encode tRNA(SerIGA), one tRNA(SerUGA), and the fourth tRNA(GlnCUG). The three serine tDNAs representing the UCN codon isoacceptor family are almost identical. However, the sequence of the tDNA(SerTGA) differs from a previously sequenced bovine tDNA(SerTGA) at 12 positions (ca. 14%). This finding suggests that in the bovine genome, two subfamilies of genes might encode tRNA(SerUGA). It also raises the possibility that new genes for a specific UCN isoacceptor might arise from the genes of a different isoacceptor, and could explain previously observed differences between species in the anticodons of coevolving pairs of tRNAs(SerUCN). The gene cluster also contains complete and partial copies, and fragments, of the BCS (bovine consensus sequence) SINE (short interspersed nuclear element) family, six examples of which were sequenced. Some of these elements occur in close proximity to two of the serine tDNAs.

The clinical management and laboratory assessment of anal warts

The results of a clinical and virological survey of anal warts from 85 predominantly homosexual or bisexual men is presented, together with an improved technique for the surgical treatment of these lesions. Two types of anal warts, which were classified as either "acute" or "chronic" on the basis of their appearance and clinical behaviour, were recognized commonly. However, our laboratory investigations--which consisted of the routine histopathological examination of all specimens, together with immunohistochemical testing for the common wart antigen of specimens from 30 patients and papillomavirus typing by human papillomavirus DNA probing of 27 specimens--failed to reveal any significant differences between the two classes of anal warts. By means of a dot hybridization technique with mixed human papillomavirus DNA probes for types 6 and 11 and types 16 and 18, all wart biopsy specimens that were tested were shown to contain human papillomavirus types 6/11; two specimens also contained human papillomavirus types 16/18. Southern blot hybridization studies of eight specimens revealed that five warts contained human papillomavirus type 6 only and three warts contained human papillomavirus type 11 only. Although the surgical technique that is described was successful in terms of patient acceptance and the eventual eradication of anal warts, there was a high rate of recurrence of the lesions, which necessitated repeat operations in two-thirds of the patients. The need for counselling before surgery and for regular follow-up examinations after surgery is discussed.

Detection of specific types of human papillomavirus in cervical scrapes, anal scrapes, and anogenital biopsies by DNA hybridization

Specific varieties of human papillomavirus (HPV) infecting the anogenital region were detected in clinical samples by use of a filter hybridization technique suitable for rapid screening of cervical and anal scrapes. In this way possibly benign types (HPV6 and HPV11) could be differentiated from types thought to be capable of malignant transformation (HPV 16 and HPV 18). Cervical or anal canal cells were applied directly to nylon filters and fixed by u.v. irradiation before hybridization with mixed viral DNA probes under both low- and high-stringency conditions. In addition, probe for the human Alu-repeated DNA sequence was used to assess the relative amount of total nucleic acids in each sample applied to the filter. HPV DNA was detected in 3 of 19 cervical scrapes from patients with no past or present history of wart virus infection or cervical dysplasia. Within a positive study group totalling 71 patients, HPV (6/11 or 16/18) was detected in cervical scrapes from 24% of 41 patients who did not have visible genital dysplasia, 30% of 27 patients with visible genital dysplasia or cervical intraepithelial neoplasia (CIN) I, and in 1 of 3 patients with past CIN II/III. In addition, HPV6/11 or 16/18 DNA was detected in anal scrapes from 3 of 6 male patients and in 85% of genital biopsies. A notably high proportion (4/6) of vaginal condylomata were positive with both the HPV6/11 and the HPV16/18 mixed viral DNA probes. Of the biopsies prepared for histopathology and positive for HPV DNA, the HPV group-specific antigen could be detected in only 60%.

Cell biology of cultured anogenital warts

A simple, reliable culture system for keratinocytes from anogenital warts is described. Using this technique we found that it was possible to produce multiple confluent keratinocyte cultures from two-thirds of the surgically-excised anogenital wart specimens received in our laboratory. Some morphological and cultural differences between these cells and normal keratinocytes derived from neonatal foreskins were observed, although there was no evidence that wart-derived keratinocytes were 'transformed'. The cultures were tested for evidence of HPV-DNA replication using 32P-labelled HPV-DNA probes, for the production of viral capsid proteins using peroxidase-antiperoxidase staining and for whole virus particles using electron microscopy. Fifty-seven per cent (8 of 14) of the wart cultures tested showed persistence of HPV-DNA (5-100 copies HPV-DNA/cell genome equivalent). However, no viral proteins or particles were detected in any culture. This system may prove to be a useful in vitro model for the study of virus-cell interaction and the role of HPV in the malignant conversion of epithelial cells.

Elevated serum levels of estrogen and prolactin in daughters of patients with breast cancer

Demographic risk factors in sisters and daughters of 150 patients with breast cancer were compared to those of controls. Plasma hormone levels in 36 teen-age daughters of patients and 31 controls were also studied to ascertain whether an "abnormal" hormone pattern underlies these risk factors. The patients' sisters had, on the average, menarche four months earlier and first full-term pregnancy 12 months later than the controls. The patients' daughters did not show these differences -- apparently owing to low fertility in the patients with early menarche. The patients' daughters had higher 22d-day estradiol-plus-estrone levels than controls (24.4 vs. 19.1 ng per 100 ml, P less than 0.05). Sixth-day prolactin was also elevated (19.0 vs. 14.2 ng per 100 ml, P less than 0.05). About half the patients' daughters could clearly be distinguished from the controls' daughters by means of the sixth-day information on both estrogens and prolactin. Hypersecretion of these hormones may be important factors in breast cancer.