Prenatal iodine supplementation and early childhood neurodevelopment: the PoppiE trial - study protocol for a multicentre randomised controlled trial

INTRODUCTION

Observational studies suggest both low and high iodine intakes in pregnancy are associated with poorer neurodevelopmental outcomes in children. This raises concern that current universal iodine supplement recommendations for pregnant women in populations considered to be iodine sufficient may negatively impact child neurodevelopment. We aim to determine the effect of reducing iodine intake from supplements for women who have adequate iodine intake from food on the cognitive development of children at 24 months of age.

METHODS AND ANALYSIS

A multicentre, randomised, controlled, clinician, researcher and participant blinded trial with two parallel groups. Using a hybrid decentralised clinical trial model, 754 women (377 per group) less than 13 weeks' gestation with an iodine intake of ≥165 µg/day from food will be randomised to receive either a low iodine (20 µg/day) multivitamin and mineral supplement or an identical supplement containing 200) µg/day (amount commonly used in prenatal supplements in Australia), from enrolment until delivery. The primary outcome is the developmental quotient of infants at 24 months of age assessed with the Cognitive Scale of the Bayley Scales of Infant Development, fourth edition. Secondary outcomes include infant language and motor development; behavioural and emotional development; maternal and infant clinical outcomes and health service utilisation of children. Cognitive scores will be compared between groups using linear regression, with adjustment for location of enrolment and the treatment effect described as a mean difference with 95% CI.

ETHICS AND DISSEMINATION

Ethical approval has been granted from the Women's and Children's Health Network Research Ethics Committee (HREC/17/WCHN/187). The results of this trial will be presented at scientific conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04586348.

Standard terminology for reproductive tissue and cell products for use in ART

Medical products of human origin (MPHO) distributed for use in assisted reproduction are currently labelled and identified using national or local systems. Products may be distributed internationally with potentially confusing identification labelling due to inconsistent terminology and definitions. In other fields of MPHO activity terminology has previously been standardized through professional collaboration as a precursor to adoption of a global standard for identification, coding and labelling. The International Council for Commonality in Blood Bank Automation (ICCBBA), an international nongovernmental organization in official relations with the World Health Organization, brought together representatives from professional societies to develop a terminology using a well-established methodology. The terminology was reviewed by professional associations and released for public comment. Further refinements were made following the comment period. Representatives of the American Society for Reproductive Medicine (ASRM), ESHRE, the Reproductive Tissue Council of the American Association of Tissue Banks (AATB) and ICCBBA met by international conference call and interacted by email. The terminology was developed using a standard model previously used across many areas of MPHO. A terminology comprising six classes, and six attribute groups has been developed. The terminology design is such that additional classes, attribute groups and attribute values can be added to meet the developing needs of the ART community. The level of detail incorporated into the terminology is based on the consensus view of the experts. The objective has been to provide sufficient detail to satisfy clinical need in product identification but there is the possibility that the level of detail may need to be adjusted in the future. The terminology is designed in a way that can readily accommodate such adjustments. Adoption of a standard terminology provides the basis for standardization of identification, coding and labelling and the use of internationally standardized barcoding to improve the accuracy and efficiency of information transfer and to reduce the risks of harm due to manual transcriptions errors.

Serine/Threonine Kinase MLK4 Determines Mesenchymal Identity in Glioma Stem Cells in an NF-κB-dependent Manner

Activation of nuclear factor κB (NF-κB) induces mesenchymal (MES) transdifferentiation and radioresistance in glioma stem cells (GSCs), but molecular mechanisms for NF-κB activation in GSCs are currently unknown. Here, we report that mixed lineage kinase 4 (MLK4) is overexpressed in MES but not proneural (PN) GSCs. Silencing MLK4 suppresses self-renewal, motility, tumorigenesis, and radioresistance of MES GSCs via a loss of the MES signature. MLK4 binds and phosphorylates the NF-κB regulator IKKα, leading to activation of NF-κB signaling in GSCs. MLK4 expression is inversely correlated with patient prognosis in MES, but not PN high-grade gliomas. Collectively, our results uncover MLK4 as an upstream regulator of NF-κB signaling and a potential molecular target for the MES subtype of glioblastomas.

Phthalate exposure and semen quality in fertile US men

Several experimental and observational studies have demonstrated the antiandrogenicity of several phthalates. However, there is limited evidence of an association between phthalate exposure in adult life and semen quality. The aim of this study was to examine phthalate exposure during adulthood in relation to semen quality in fertile US men. This multi-center cross-sectional study included 420 partners of pregnant women who attended a prenatal clinic in one of five US cities during 1999-2001. Nine phthalate metabolites [mono (2-ethylhexyl) phthalate (MEHP), mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono (2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono (2-ethyl-5-carboxypentyl) phthalate (MECPP)], as well as mono-n-butyl phthalate (MBP) and mono-isobutyl phthalate (MiBP), mono (three carboxypropyl) phthalate (MCPP), monobenzyl phthalate (MBzP), and monoethyl phthalate (MEP)] were measured in urine collected at the same time as the semen sample. We regressed natural log-transformed (ln) sperm concentration, ln(total sperm count), ln(total motile sperm count), percent motile spermatozoa, and percent spermatozoa with normal morphology on each of the nine natural log-transformed metabolite concentrations and on the molar-weighted sum of DEHP metabolites in separate models. We fit unadjusted models and models that adjusted for confounders determined a priori. In unadjusted models, ln(MiBP) was significantly and positively associated with motility and ln(MBzP) significantly negatively associated with ln(total sperm count). In adjusted linear models, urinary metabolite concentrations of DEHP, DBP, DEP, and DOP were not associated with any semen parameter. We found an inverse association between ln(MBzP) concentrations and sperm motility (β = -1.47, 95% CI: -2.61, -0.33), adjusted for ln(creatinine concentration), geographic location, age, race, smoking status, stress, recent fever, time from sample collection and time to complete analysis. Several sensitivity analyses confirmed the robustness of these associations. This study and the available literature suggest that impacts of adult exposure to phthalates at environmental levels on classical sperm parameters are likely to be small.

The degradation of p53 and its major E3 ligase Mdm2 is differentially dependent on the proteasomal ubiquitin receptor S5a

p53 and its major E3 ligase Mdm2 are both ubiquitinated and targeted to the proteasome for degradation. Despite the importance of this in regulating the p53 pathway, little is known about the mechanisms of proteasomal recognition of ubiquitinated p53 and Mdm2. In this study, we show that knockdown of the proteasomal ubiquitin receptor S5a/PSMD4/Rpn10 inhibits p53 protein degradation and results in the accumulation of ubiquitinated p53. Overexpression of a dominant-negative deletion of S5a lacking its ubiquitin-interacting motifs (UIM)s, but which can be incorporated into the proteasome, also causes the stabilization of p53. Furthermore, small-interferring RNA (siRNA) rescue experiments confirm that the UIMs of S5a are required for the maintenance of low p53 levels. These observations indicate that S5a participates in the recognition of ubiquitinated p53 by the proteasome. In contrast, targeting S5a has no effect on the rate of degradation of Mdm2, indicating that proteasomal recognition of Mdm2 can be mediated by an S5a-independent pathway. S5a knockdown results in an increase in the transcriptional activity of p53. The selective stabilization of p53 and not Mdm2 provides a mechanism for p53 activation. Depletion of S5a causes a p53-dependent decrease in cell proliferation, demonstrating that p53 can have a dominant role in the response to targeting S5a. This study provides evidence for alternative pathways of proteasomal recognition of p53 and Mdm2. Differences in recognition by the proteasome could provide a means to modulate the relative stability of p53 and Mdm2 in response to cellular signals. In addition, they could be exploited for p53-activating therapies. This work shows that the degradation of proteins by the proteasome can be selectively dependent on S5a in human cells, and that this selectivity can extend to an E3 ubiquitin ligase and its substrate.

Semen parameters in fertile US men: the Study for Future Families

Establishing reference norms for semen parameters in fertile men is important for accurate assessment, counselling and treatment of men with male factor infertility. Identifying temporal or geographic variability in semen quality also requires accurate measurement of semen parameters in well-characterized, defined populations of men. The Study for Future Families (SFF) recruited men who were partners of pregnant women attending prenatal clinics in Los Angeles CA, Minneapolis MN, Columbia MO, New York City NY and Iowa City IA. Semen samples were collected on site from 763 men (73% White, 15% Hispanic/Latino, 7% Black and 5% Asian or other ethnic group) using strict quality control and well-defined protocols. Semen volume (by weight), sperm concentration (hemacytometer) and sperm motility were measured at each centre. Sperm morphology (both WHO, 1999 strict and WHO, 1987) was determined at a central laboratory. Mean abstinence was 3.2 days. Mean (median; 5th-95th percentile) values were: semen volume, 3.9 (3.7; 1.5-6.8) mL; sperm concentration, 60 (67; 12-192) × 10(6) /mL; total sperm count 209 (240; 32-763) × 10(6) ; % motile, 51 (52; 28-67) %; and total motile sperm count, 104 (128; 14-395) × 10(6) respectively. Values for sperm morphology were 11 (10; 3-20) % and 57 (59; 38-72) % normal forms for WHO (1999) (strict) and WHO (1987) criteria respectively. Black men had significantly lower semen volume, sperm concentration and total motile sperm counts than White and Hispanic/Latino men. Semen parameters were marginally higher in men who achieved pregnancy more quickly but differences were small and not statistically significant. The SFF provides robust estimates of semen parameters in fertile men living in five different geographic locations in the US. Fertile men display wide variation in all of the semen parameters traditionally used to assess fertility potential.

Lack of cortico-limbic coupling in bipolar disorder and schizophrenia during emotion regulation

Bipolar disorder (BD) and schizophrenia (Sz) share dysfunction in prefrontal inhibitory brain systems, yet exhibit distinct forms of affective disturbance. We aimed to distinguish these disorders on the basis of differential activation in cortico-limbic pathways during voluntary emotion regulation. Patients with DSM-IV diagnosed Sz (12) or BD-I (13) and 15 healthy control (HC) participants performed a well-established emotion regulation task while undergoing functional magnetic resonance imaging. The task required participants to voluntarily upregulate or downregulate their subjective affect while viewing emotionally negative images or maintain their affective response as a comparison condition. In BD, abnormal overactivity (hyperactivation) occurred in the right ventrolateral prefrontal cortex (VLPFC) during up- and downregulation of negative affect, relative to HC. Among Sz, prefrontal hypoactivation of the right VLPFC occurred during downregulation (opposite to BD), whereas upregulation elicited hyperactivity in the right VLPFC similar to BD. Amygdala activity was significantly related to subjective negative affect in HC and BD, but not Sz. Furthermore, amygdala activity was inversely coupled with the activity in the left PFC during downregulation in HC (r=-0.76), while such coupling did not occur in BD or Sz. These preliminary results indicate that differential cortico-limbic activation can distinguish the clinical groups in line with affective disturbance: BD is characterized by ineffective cortical control over limbic regions during emotion regulation, while Sz is characterized by an apparent failure to engage cortical (hypofrontality) and limbic regions during downregulation.

p53 is activated in response to disruption of the pre-mRNA splicing machinery

In this study, we show that interfering with the splicing machinery results in activation of the tumour-suppressor p53. The spliceosome was targeted by small interfering RNA-mediated knockdown of proteins associated with different small nuclear ribonucleoprotein complexes and by using the small-molecule splicing modulator TG003. These interventions cause: the accumulation of p53, an increase in p53 transcriptional activity and can result in p53-dependent G(1) cell cycle arrest. Mdm2 and MdmX are two key repressors of p53. We show that a decrease in MdmX protein level contributes to p53 activation in response to targeting the spliceosome. Interfering with the spliceosome also causes an increase in the rate of degradation of Mdm2. Alterations in splicing are linked with tumour development. There are frequently global changes in splicing in cancer. Our study suggests that p53 activation could participate in protection against potential tumour-promoting defects in the spliceosome. A number of known p53-activating agents affect the splicing machinery and this could contribute to their ability to upregulate p53. Preclinical studies indicate that tumours can be more sensitive than normal cells to small-molecule spliceosome inhibitors. Activation of p53 could influence the selective anti-tumour activity of this therapeutic approach.

Cognitive regulation of emotion in bipolar I disorder and unaffected biological relatives

OBJECTIVE

We examined the use of particular cognitive strategies for regulating negative emotion in relation to mood and temperament in BD-I, unaffected relatives of bipolar patients (UR), and healthy controls (HC).

METHOD

Participants were 105 patients with BD-I, 124 UR, and 63 HC; all participants completed the Cognitive Emotion Regulation Questionnaire (CERQ), the Depression Anxiety Stress Scales (DASS), and the Hypomanic Personality Scale (HPS).

RESULTS

The BD-I group reported more frequent use of rumination, catastrophizing and self-blame, and less frequent use of putting into perspective, in response to negative life events, relative to the UR and HC groups. In BD-I, more frequent use of rumination was associated with increased DASS and HPS scores. By contrast, within the UR group, more frequent use of catastrophizing and self-blame were associated with increased DASS and HPS scores. In all participants, less frequent use of adaptive cognitive reframing strategies (e.g. putting into perspective) were associated with increased DASS scores.

CONCLUSION

Both BD-I and UR groups reported more frequent use of maladaptive regulatory strategies previously associated with depression. Emotion regulation strategies of catastrophizing, self-blame, and cognitive reframing techniques may be associated with vulnerability for mood disorders, with the latter active within the general population regardless of biological vulnerability to disorder.

Associations between urinary metabolites of di(2-ethylhexyl) phthalate and reproductive hormones in fertile men

Widely used man-made chemicals, including phthalates, can induce hormonal alterations through a variety of cellular and molecular mechanisms. A number of rodent and observational studies have consistently demonstrated the anti-androgenic effect of several phthalates. However, there are only limited data on the relationship between exposure to these chemicals and reproductive hormone levels in men. All men (n=425) were partners of pregnant women who participated in the Study for Future Families in five US cities and provided urine and serum samples on the same day. Eleven phthalate metabolites were measured in urine and serum samples were analysed for reproductive hormones, including follicle-stimulating hormone, luteinizing hormone, testosterone, inhibin B and oestradiol and sex hormone-binding globulin (SHBG). Pearson correlations and parametric tests were used for unadjusted analyses, and multiple linear regression analysis was performed controlling for appropriate covariates. We observed weak or no associations with urinary phthalates other than di(2-ethylhexyl) phthalate (DEHP). All measures of testosterone [total, calculated free testosterone and the free androgen index (FAI)] were inversely correlated with the urinary concentrations of four DEHP metabolites. After adjustment by appropriate covariates, there was no longer an association between urinary DEHP metabolite concentrations and total testosterone levels; however, FAI was significantly associated with the urinary concentrations of several DEHP metabolites. SHBG was positively related to the urinary concentrations of mono(2-ethylhexyl) phthalate, but not with other DEHP metabolites, an association that was attenuated after adjustment. Our results suggest that DEHP exposure of fertile men is associated with minor alterations of markers of free testosterone.

Prenatal phthalate exposure and reduced masculine play in boys

Foetal exposure to antiandrogens alters androgen-sensitive development in male rodents, resulting in less male-typical behaviour. Foetal phthalate exposure is also associated with male reproductive development in humans, but neurodevelopmental outcomes have seldom been examined in relation to phthalate exposure. To assess play behaviour in relation to phthalate metabolite concentration in prenatal urine samples, we recontacted participants in the Study for Future Families whose phthalate metabolites had been measured in mid-pregnancy urine samples. Mothers completed a questionnaire including the Pre-School Activities Inventory, a validated instrument used to assess sexually dimorphic play behaviour. We examined play behaviour scores (masculine, feminine and composite) in relationship to (log(10)) phthalate metabolite concentrations in mother's urine separately for boys (N = 74) and girls (N = 71). Covariates (child's age, mother's age and education and parental attitude towards atypical play choices) were controlled using multivariate regression models. Concentrations of dibutyl phthalate metabolites, mono-n-butyl phthalate (MnBP) and mono-isobutyl phthalate (MiBP) and their sum, were associated with a decreased (less masculine) composite score in boys (regression coefficients -4.53,-3.61 and -4.20, p = 0.01, 0.07 and 0.04 for MnBP, MiBP and their sum respectively). Concentrations of two urinary metabolites of di(2-ethylhexyl) phthalate (DEHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) and mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and the sum of these DEHP metabolites plus mono(2-ethylhexyl) phthalate were associated with a decreased masculine score (regression coefficients -3.29,-2.94 and -3.18, p = 0.02, 0.04 and 0.04) for MEHHP, MEOHP and the sum respectively. No strong associations were seen between behaviour and urinary concentrations of any other phthalate metabolites in boys, or between girls' scores and any metabolites. These data, although based on a small sample, suggest that prenatal exposure to antiandrogenic phthalates may be associated with less male-typical play behaviour in boys. Our findings suggest that these ubiquitous environmental chemicals have the potential to alter androgen-responsive brain development in humans.

Binding to intracellular targets of the metastasis-inducing protein, S100A4 (p9Ka)

Experimentally elevated levels of S100A4 induce a metastatic phenotype in benign mammary tumour cells in vivo. In humans, the presence of S100A4 in breast cancer cells correlates strongly with reduced patient survival. Potential interacting binding partners for S100A4 have now been examined using an optical biosensor. There was significant interaction of S100A4 with non-muscle myosin and p53, but not with actin, tropomyosin or tubulin. The results suggest that myosin and p53 are likely to be intracellular targets of S100A4. S100A4 had a greater affinity for wild-type or mutant arg-175-his p53 than for non-muscle myosin. The results suggest that S100A4 might induce metastasis by influencing the function of p53 as well as through its interaction with myosin and that any mechanism is independent of the mutational status of p53.

Public health response to an incident of secondary chemical contamination at a beach in the United Kingdom

OBJECTIVES

To gather enough data from a large scale investigation involving two health authorities, to assess the possible concentrations and routes of exposure and the consequent health implications. To use the data to decide whether a polluted beach should remain open to the public. In Spring 1997, a chemical incident came to light at a beach on the south coast of England when a local resident reported a sulphurous smell, visible signs of oil, and reduced numbers of fishing bait. The beach was situated adjacent to a former gasworks site and was accessible to the public. The incident was reported to the local authority and was initially investigated by the Environment Agency and the local authority. An Environment Agency report confirmed contamination of the beach with cyanide, ammonia, and polycyclic aromatic hydrocarbons (PAHs) with associated potential health risks. The incident was then referred to the local health authorities for investigation.

METHODS

The investigation was carried out in four stages: comprehensive sampling and analysis to identify the extent of contamination, followed by an assessment of risk to health; establishment of a long term monitoring programme to identify any changes in contaminant concentrations; investigation of the effects of the contamination on shellfish; and review of the routine monitoring data and current sampling strategy.

RESULTS

The initial investigation confirmed that the beach was contaminated, with the most likely source being the adjacent former gasworks site. The level of contamination was not found to be likely to pose a hazard to users of the beach. However, subsequent investigation of shellfish in the area led to warning signs being erected on the beach to prevent human consumption of mussels contaminated with PAHs.

CONCLUSIONS

Several lessons can be learnt from this investigation, which can be applied to incident management more generally: the importance of collaboration and coordination; the need for early involvement of the health authority; and the importance of carrying out appropriate sampling and analysis as soon as possible, to assess the risk to health and the environment.

Defective nuclear localization of p53 protein in a Chinese hamster cell line is associated with the formation of stable cytoplasmic protein multimers in cells with gene amplification

Many p53 functions require p53 transport into the nucleus. Mutant p53 also generally accumulates in the nucleus of transformed or neoplastic cells. However, examples of cytoplasmic accumulation of wild-type or mutant p53 have also been reported. Various explanations have been provided for defective nuclear localization. Here we propose a novel example of cytoplasmic p53 localization which occurs in cells showing gene amplification and appears to be due to the formation of stable p53 multimers. We studied a methotrexate-resistant Chinese hamster cell line (MTX M) carrying amplified dihydrofolate reductase genes and derived from a cell line with p53 nuclear accumulation. MTX M showed cytoplasmic p53 localization and, on immunoblots, several extra bands in the high molecular weight region, besides the expected 53 kDa band. p53 localization and the appearance of high molecular weight bands appeared to be correlated with the degree of DNA amplification. However, amplification of dihydrofolate reductase itself was not involved. Changing the p53 phosphorylation status quantitatively influenced the formation of high molecular weight bands. Cell fusion experiments demonstrated that p53 cytoplasmic localization in MTX M is a dominant phenotype. This result suggests that the defect causing lack of nuclear localization in this cell line does not reside in the nucleus. In the cytoplasm of MTX M and of wild-type/MTX M heterodikaryons p53 gives rise to protein complexes that are unable to re-enter the nucleus. The formation of such protein complexes is dependent on the amplification of an unknown gene product.

Analysis of adenomatous polyposis coli promoter hypermethylation in human cancer

Germ-line mutations in the tumor suppressor gene APC are associated with hereditary familial adenomatous polyposis (FAP), and somatic mutations are common in sporadic colorectal tumors. We now report that methylation in the promoter region of this gene constitutes an alternative mechanism for gene inactivation in colon and other tumors of the gastrointestinal tract. The APC promoter is hypermethylated in 18% of primary sporadic colorectal carcinomas (n = 108) and adenoma (n = 48), and neoplasia with APC methylation fails to express the APC transcript. Methylation affects only wild-type APC in 95% of cases and is not observed in tumors from FAP patients who have germ-line APC mutations. As with APC mutation, aberrant APC methylation occurs early in colorectal carcinogenesis. When other tumor types are analyzed (n = 208), methylation of the APC promoter is not restricted to the colon but is present in tumors originating elsewhere in the gastrointestinal tract but rarely in other tumors. Our data suggest that hypermethylation of APC provides an important mechanism for impairing APC function and further underscores the importance of the APC pathway in gastrointestinal tumorigenesis.

An N-terminal p14ARF peptide blocks Mdm2-dependent ubiquitination in vitro and can activate p53 in vivo

The p53 tumour suppressor protein is down-regulated by the action of Mdm2, which targets p53 for rapid degradation by the ubiquitin-proteasome pathway. The p14ARF protein is also a potent tumour suppressor that acts by binding to Mdm2 and blocking Mdm2-dependent p53 degradation and transcriptional silencing. We have screened a series of overlapping synthetic peptides derived from the p14ARF protein sequence and found that a peptide corresponding to the first 20 amino acids of ARF (Peptide 3) could bind human Mdm2. The binding site for Peptide 3 on Mdm2 was determined by deletion mapping and lies adjacent to the binding site of the anti-Mdm2 antibody 2A10, which on microinjection into cells can activate p53-dependent transactivation of a reporter plasmid. To determine whether Peptide 3 could similarly activate p53, we expressed a fusion of green fluorescent protein and Peptide 3 in MCF7 and U-2 OS cells and were able to demonstrate induction of p53 protein and p53-dependent transcription. Peptide 3 was able to block in vitro ubiquitination of p53 mediated by Mdm2. Small peptides which are sufficient to block degradation of p53 could provide therapeutic agents able to restore p53-dependent cell death pathways in tumours that retain wild-type p53 expression.

Transcription factor E2F-1 is upregulated in response to DNA damage in a manner analogous to that of p53

The transcription factor E2F-1 directs the expression of genes that induce or regulate cell division, and a role for E2F-1 in driving cells into apoptosis is the subject of intense discussion. Recently it has been shown that E2F-1 binds and coprecipitates with the mouse double-minute chromosome 2 protein (Mdm2). A domain of E2F-1 (amino acids 390 to 406) shows striking similarity to the Mdm2 binding domain of the tumor suppressor protein p53. It is known that interaction of Mdm2 with p53 through this domain is required for Mdm2-dependent degradation of p53. We show here that E2F-1 protein is upregulated in response to DNA damage. The kinetics of induction are dependent upon the source of DNA damage, i.e., fast and transient after irradiation with X rays and delayed and stable after irradiation with UVC, and thus match the kinetics of p53 induction in response to DNA damage. We show further that E2F-1 is also upregulated by treatment with the transcription inhibitor actinomycin D and with the kinase inhibitor DRB, as well as by high concentrations of the kinase inhibitor H7, all conditions which also upregulate p53. In our experiments we were not able to see an increase in E2F-1 RNA production but did find an increase in protein stability in UVC-irradiated cells. Upregulation of E2F-1 in response to DNA damage seems to require the presence of wild-type p53, since we did not observe an increase in the level of E2F-1 protein in several cell lines which possess mutated p53. Previous experiments showed that p53 is upregulated after microinjection of an antibody which binds to a domain of Mdm2 that is required for the interaction of Mdm2 with p53. Microinjection of the same antibody also increases the expression of E2F-1 protein, while microinjection of a control antibody does not. Furthermore, microinjection of Mdm2 antisense oligonucleotides upregulates E2F-1 protein, while microinjection of an unrelated oligonucleotide does not. These data suggest that E2F-1 is upregulated in a similar way to p53 in response to DNA damage and that Mdm2 appears to play a major role in this pathway.

An inhibitor of nuclear export activates the p53 response and induces the localization of HDM2 and p53 to U1A-positive nuclear bodies associated with the PODs

Leptomycin B is a cytotoxin which directly interacts with and inhibits the action of CRM1, an essential mediator of the nuclear exit of proteins containing nuclear export signals (NES) of the HIV1 REV type. We show that addition of leptomycin B to human primary fibroblasts increased the levels of the p53 tumor suppressor protein. This was accompanied by the induction of p53-dependent transcriptional activity in cultured cells and an increase in the levels of the products of two p53-responsive genes, the p21(CIP1/WAF1) and HDM2 proteins. Leptomycin B induced the accumulation of p53 and HDM2 in the nucleus and the appearance of discrete nuclear aggregates containing both proteins. It has been reported that the transcriptional activity of p53 is modulated by its interaction with the HDM2 protein which also targets p53 for rapid degradation. Using a model cell line conditionally expressing MDM2, the murine analogue of HDM2, we present evidence indicating that leptomycin B abrogates MDM2's role in p53 degradation and that the accumulation of p53 in distinct nuclear bodies is mediated by MDM2. Since HDM2 has recently been shown to contain a functional NES of the REV type, the most likely explanation for our results is that the effect of leptomycin B on HDM2 and p53 is due to the inhibition of nuclear export. The ability to visualize sites where p53 and HDM2 colocalize provides a new approach to study the association between the two proteins in vivo. These p53/HDM2-positive nuclear foci were found to also contain the U1A snRNP A and to be juxtaposed to the PML oncogenic domains.

Design of a synthetic Mdm2-binding mini protein that activates the p53 response in vivo

BACKGROUND

The transcriptional activation function of the p53 tumour suppressor protein is induced by DNA damage and results in growth arrest and/or apoptotic responses. A key component of this response is the dramatic rise in p53 protein concentration resulting from an increase in the protein's stability. Very recently, it has been suggested that interaction with the Mdm2 protein may target p53 for rapid degradation. We have designed a gene encoding a small protein that binds tightly to the p53-binding pocket on the Mdm2 protein. We have constructed the gene by cloning a phage display optimised Mdm2-binding peptide into the active-site loop of thioredoxin.

RESULTS

When introduced into cells containing low levels of wild-type p53, this protein causes a striking accumulation of the endogenous p53 protein, activation of a p53-responsive reporter gene, and cell cycle arrest mimicking the effects seen in these cells after exposure to UV or ionising radiation. Microinjection of a monoclonal antibody to the p53-binding site on Mdm2 achieves a similar effect, establishing its specificity.

CONCLUSIONS

These results demonstrate that the p53 response is constitutively regulated in normal cells by Mdm2 and that disruption of the interaction alone is sufficient to stabilise the p53 protein and activate the p53 response. Our mini protein approach provides a powerful new method to activate p53 without causing DNA damage. More broadly, it establishes a powerful general method for determining the biological consequences of the specific disruption of protein-protein interactions in cells.

Epitope analysis of the murine p53 tumour suppressor protein

The identification and characterisation of the p53 tumour suppressor has relied extensively on the use of immunological reagents. To facilitate further characterisation of the murine p53 protein (Mp53), and its interaction with other proteins, we have characterised the antigenic sites of Mp53 in fine detail. Using an overlapping Mp53 peptide library we report the identification by Pepscan ELISA of the epitopes of nine antibodies. We have also used this technique to determine whether corresponding epitopes were present in a human p53 (Hp53) peptide library. This comparison was extended to include polyclonal sera of mice immunized with either Mp53 or Hp53, to compare the overall range of antigenic sites. The range of antigenic sites identified by polyclonal sera is very similar, although the N-terminus of Mp53 is clearly not an immunodominant region, in contrast to the N-terminus of Hp53. However, the N-terminus of Mp53 is immunogenic in rabbits as demonstrated by the Pepscan ELISA of CM5 serum (a rabbit anti-Mp53 serum used in analysing p53 expression in mice). Since, very few new antigenic sites were identified in either Mp53 or Hp53, new approaches will have to be employed to identify novel immunological reagents against human and murine p53.

Small peptides activate the latent sequence-specific DNA binding function of p53

Normal cells contain p53 protein in a latent state that can be activated for sequence-specific transcription by low levels of UV radiation without an increase in protein levels. Microinjection of cells with an antibody specific to the C-terminal negative regulatory domain can activate the function of p53 as a specific transcription factor in the absence of irradiation damage, suggesting that posttranslational modification of a negative regulatory domain in vivo is a rate-limiting step for p53 activation. Small peptides derived from the negative regulatory domain of p53 have been used as biochemical tools to distinguish between allosteric and steric mechanisms of negative regulation of p53 tetramer activity. Presented is the development of a highly specific peptide activation system that is consistent with an allosteric mechanism of negative regulation and that forms a precedent for the synthesis of novel low molecular mass modifiers of the p53 response.

Immunochemical analysis of the interaction of p53 with MDM2;--fine mapping of the MDM2 binding site on p53 using synthetic peptides

The function of p53 is modulated by binding to a number of cellular and viral proteins, such as MDM2 and SV40 large T antigen. An initial immunochemical characterization of the p53-MDM2 complex in a rat fibroblast cell line (Clone 6) suggested that the anti-p53 monoclonal antibody Bp53-19 failed to immunoprecipitate the complex, and only recognized a fraction of the available p53 protein. Following the recent identification of the Bp53-19 epitope at the N-terminal end of p53, in the vicinity of where MDM2 protein was known to bind, we investigated the possibility that Bp53-19 might identify a region of p53 that interacts with MDM2 protein. MDM2 was found to bind with great specificity to short synthetic peptides derived from the N-terminus of p53. Several p53 synthetic peptides libraries, and an alanine substitution series at the optimal binding site, were used to establish the MDM2 binding site, in fine detail, to the sequence TFSGLW (aa 18-23) in mouse and TFSDLW in man (aa 18-23). The key residues required for MDM2 binding are almost identical to those required for the monoclonal antibody Bp53-19 to bind and this region of p53 is recognised by many other anti-p53 antibodies.

Fifth International Symposium on Bioluminescence and Chemiluminescence. Florence-Bologna, Italy, September, 1988. Proceedings

With the advent of enzymatically induced chemiluminescence and improved instrumentation for luminometry, ultrasensitive detection of a wide variety of analytes is now possible using standard immunoassay and DNA probe formats. Model molecular orbital calculations and literature precedent suggest that the singlet efficiencies observed upon decomposition of dioxetanes appended with donor substituted aromatic moieties are dependent on substitution pattern. We have recently discovered, in a series of 3-(2'-spiroadamantane)-4-methoxy-4-acetoxynaphth-2'-yl-1,2-+ ++dioxetanes, that enzymatic generation of a non-conjugated, charge transfer excited state results in luminescence of markedly different properties than that observed from an isomeric, conjugated excited state. An example of the former type, 3-(2'-spiroadamantane)-4-methoxy-4-(7"-acetoxy)naphth-2'-yl- 1,2- dioxetane (1) emitting at 550 nm, not only provides an increase in phi CL, but exhibits a dramatic bathochromic shift of 80-110 nm from the 460 nm emission of the conjugated isomer 3-(2'-spiroadamantane)-4-methoxy-4-(6"-acetoxy)naphth-2'-yl- 1,2-dioxetane (2). These developments, along with the attendant glow-type luminescence kinetics displayed during the enzymatic decomposition of the new 'odd-pattern' dioxetane, allow the design of simple protocols capable of simultaneous or 'multichannel' detection of several analytes.

Rape crisis program helps restore dignity and control

A rape victim often finds herself in a hospital emergency room before she even has a chance to think about what happened, how she feels, or what she needs. Emergency rooms are not equipped to help restore the victim's feelings of safety, dignity, and control over her life. To remedy that situation, St. Vincent's Hospital and Medical Center of New York instituted the Rape Crisis Program in 1977. The program, staffed by two professional social workers, an administrative assistant, and a student doing field work, offers counseling as an enabling, healing process in which the client actively participates. Two aspects of the counseling are particularly important: providing a perspective on the recovery process and helping the survivor discuss details of the assault that she would not want to tell anyone else. Volunteers assist victims in the emergency room at night and on weekends after completing eight training sessions of 2 1/2 hours each. Readings, discussion, and role playing help trainees understand the fear, anger, and shame that sexual assault victims experience. Sometimes victims return to help others by becoming volunteers.