[Study of the psychometric properties of the CES-D in a sample of French-speaking adolescents]. / Étude des propriétés psychométriques de l'échelle CES-D sur un échantillon d'adolescents francophones scolarisés.

UNLABELLED: The aim of this paper is to study and validate the French version of the Center for Epidemiologic Studies Depression Scale developed by Radloff (in 1977) in an adolescent sample. This scale was developed to measure levels of depressive symptomatology, with special emphasis on the affective components and depressed mood. METHOD: The data used in this study were collected in 11 schools. Our sample was composed of 1496 French-speaking, Belgian secondary school students aged 12 to 16 years. The questionnaire included demographic information such as age, gender, grade and family composition. The position of the CES-D scale has not changed and was placed in the last part of the self-administered questionnaire. RESULTS: After an exploratory factor analysis, we conducted confirmatory factor analysis to test our factor model. We tested the model with four factors proposed by Radloff (in 1977) and also the model proposed by Chabrol (in 2002). Our results indicate a better match with Radloff's model in our sample, showing the relevance of using Radloff's model with four factors in adolescents. Although our analysis shows a clear gender difference with regard to depressive symptoms, the tested factor model remained stable regardless of the gender of the adolescent.

[Mechanisms of indeterminacy between the imaginary and the rational worlds in schizophrenic subjects]. / Mécanismes d'indifférenciation entre l'imaginaire et le rationnel chez le schizophrène.

INTRODUCTION: Our investigation into dream and delirium in schizophrenic subjects was based on the notion of magical thought developed by Sami-Ali. Starting from this notion, we attempted to determine whether they somehow differentiate the psychic space of dream from that of delirium, whether either of these two spaces, or both, are caught in a relational deadlock, and eventually to analyse the quality of the relationship to others. HYPOTHESIS: The underlying assumption is that magical thought is foregrounded in the psychic life of schizophrenic subjects, and that these subjects do not distinguish between the psychic spaces of dream and delirium, nor between the world, others, and themselves. RESULTS: Results show first that the prevalence of magical thought has the following consequences: (a) features characterizing space are those of an imaginary space, i.e. internal and external realities are blurred, what is outside is reflected inside, and vice versa, the subject-object distinction is cancelled to leave one single reality that ignores contradiction; (b) the time of discourse is an imaginary time: their discourses express past and future as belonging to an absolute "perpetual" present. Events they mention are experienced as contemporary. Causal relations, being imaginary, can be reversed. However, some socially sanctioned landmarks in time are often maintained. These are rarely related to any event in their own emotional lives. Second, our results provide evidence for some permeability between the space of dream and the space of delirium. Yet, this permeability can vary from one subject to another. Third, they show that relational deadlocks recur regularly, though not systematically, in the lives of our subjects. Relational deadlocks in dreams are not easy to detect. DISCUSSION: Finally, the kind of relationship those people have to others is quite paradoxical: physical closeness results in emotional distance, and conversely emotional closeness is only possible in physical distance. The others cannot really exist in the relationship; they are a horizon towards which those people yearn without ever being able to reach it. This kind of paradox, of relational deadlock, may be the ground on which psychosis thrives: it is impossible to be close to the nonself, while it is also deeply wished for. Even the logic of imaginary space - in which everything should be possible - cannot help overcome this paradox. And - a paradox within the paradox - this logic still comes upon a deadline in the potentially infinite and indefinite space it produces. This boundary could be the deadlock that cannot and yet must be overcome, a deadlock that would endlessly fuel the patients' delirium.

[Effect of previous culture conditions and the presence of the rpoS gene on the survival of Salmonella typhimurium in sea water exposed to sunlight]. / Influence des conditions de culture préalables et de la présence du gène rpoS pour la survie de Salmonella typhimurium en eau de mer exposée à la lumière solaire.

The effect of sunlight exposure on Salmonella typhimurium isogenic strains harboring an rpoS gene functional (rpoS+) or not functional (rpoS-) was investigated in microcosms of sterile sea water at 20 degrees C. The two strains rapidly lost their ability to produce colonies on solid culture media. The detrimental action of sunlight was more important when the salinity of sea water increased. The survival of stationary phase cells was influenced by RpoS. Bacteria grown in media with high salinity or osmolarity and transferred to sea water in stationary phase were more resistant to irradiation than those grown in media with low salinity. Prior growth under oxidative (0.2 mmol/L of H2O2) or amino acid starved (minimal medium) conditions did not modify the survival of either strain when they were exposed to sunlight. Bacteria were more resistant when cells were incubated in sea water in the dark prior to being exposed to sunlight. The resistance to sunlight irradiation was also greater in clones of both strains isolated from microcosms exposed to sunlight for 90 min, then further inoculated into sea water and reexposed to sunlight.

Protein--protein interaction maps: a lead towards cellular functions.

The availability of complete genome sequences now permits the development of tools for functional biology on a proteomic scale. Several experimental approaches or in silico algorithms aim at clustering proteins into networks with biological significance. Among those, the yeast two-hybrid system is the technology of choice to detect protein-protein interactions. Recently, optimized versions were applied at a genomic scale, leading to databases on the web. However, as with any other 'genetic' assay, yeast two-hybrid assays are prone to false positives and false negatives. Here we discuss these various technologies, their general limitations and the potential advances they make possible, especially when in combination with other functional genomics or bioinformatics analyses.

c-Jun interacts with the corepressor TG-interacting factor (TGIF) to suppress Smad2 transcriptional activity.

The Sma and Mad related (Smad) family proteins are critical mediators of the transforming growth factor-beta (TGF-beta) superfamily signaling. After TGF-beta-mediated phosphorylation and association with Smad4, Smad2 moves to the nucleus and activates expression of specific genes through cooperative interactions with DNA-binding proteins, including members of the winged-helix family of transcription factors, forkhead activin signal transducer (FAST)-1 and FAST2. TGF-beta has also been described to activate other signaling pathways, such as the c-Jun N-terminal Kinase (JNK) pathway. Here, we show that activation of JNK cascade blocked the ability of Smad2 to mediate TGF-beta-dependent activation of the FAST proteins. This inhibitory activity is mediated through the transcriptional factor c-Jun, which enhances the association of Smad2 with the nuclear transcriptional corepressor TG-interacting factor (TGIF), thereby interfering with the assembly of Smad2 and the coactivator p300 in response to TGF-beta signaling. Interestingly, c-Jun directly binds to the nuclear transcriptional corepressor TGIF and is required for TGIF-mediated repression of Smad2 transcriptional activity. These studies thus reveal a mechanism for suppression of Smad2 signaling pathway by JNK cascade through transcriptional repression.

c-Jun inhibits transforming growth factor beta-mediated transcription by repressing Smad3 transcriptional activity.

Transforming growth factor beta (TGF-beta) is a pleiotropic cytokine that exerts its effects through a heteromeric complex of transmembrane serine/threonine kinase receptors. At least two intracellular pathways are activated by TGF-beta as follows: the SAPK/JNK, involving the MEKK1, MKK4, and JNK cascade, and the Smad pathway. Here, we report that the SAPK/JNK pathway inhibits the Smad3 pathway. Expression of dominant negative or constitutively active mutants of kinases of the SAPK/JNK pathway, respectively, activates or represses a TGF-beta-induced reporter containing Smad3-binding sites. This effect is not dependent on blocking of Smad3 nuclear translocation but involves a functional interaction between Smad3 and c-Jun, a transcription factor activated by the SAPK/JNK pathway. Overexpression of constitutively active MEKK1 or MKK4 mutants stabilizes the physical interaction between Smad3 and c-Jun, whereas dominant negative mutants inhibit this interaction. Moreover, overexpression of wild-type c-Jun inhibits Smad3-dependent transcription. However, c-Jun does not inhibit Smad3 binding to DNA in vitro. The repression obtained with a c-Jun mutant unable to activate transcription through AP-1 sites indicates that the inhibitory mechanism does not rely on the induction of a Smad3 repressor by c-Jun, suggesting that c-Jun could act as a Smad3 co-repressor. The inhibition of the Smad3 pathway by the SAPK/JNK pathway, both triggered by TGF-beta, could participate in a negative feedback loop to control TGF-beta responses.

Biomarkers of DNA damage in marine mammals.

Certain environmental contaminants found in marine mammals have been shown to cause DNA damage and cancer. The micronuclei (MN), sister chromatid exchange (SCE) and/or chromosome aberration (CA) assays were used to assess baseline (spontaneous) levels of DNA damage in blood lymphocytes of individuals of the relatively healthy and lightly contaminated Arctic beluga whale (Delphinapterus leucas), Sarasota Bay, FL, bottlenose dolphin (Tursiops truncatus) and Northwestern Atlantic grey (Halichoerus grypus) and harp (Phoca groenlandicus) seal populations. MN cell (MNC) frequencies ranged between 2 and 14/1000 binucleated (BN) cells and were statistically similar between species. In bottlenose dolphins, MNC frequency was correlated with age and was significantly higher in females than in males. No intraspecific variation in MNC frequency was found in beluga whales. Intraspecific variation was not tested in seals due to the small sample size. Frequencies of SCEs and total CAs, excluding gaps, ranged, respectively, between 1 and 15 SCE(s)/per cell and 4-6 CAs/100 cells in beluga whales. SCE and CA frequencies did not vary with age or sex in beluga whales. The MN, SCE and CA assays were found to be practical tools for the detection of DNA damage in marine mammals and could be used in the future to compare DNA damage between relatively lightly and highly contaminated populations.

Expression of connective tissue growth factor in experimental rat and human liver fibrosis.

Connective tissue growth factor (CTGF) stimulates in vitro fibroblast proliferation and extracellular matrix synthesis. The aim of this study was to assess the role of CTGF in liver fibrogenesis. CTGF expression was investigated both at the protein and mRNA level in biopsies of chronic liver diseases, in experimental models of liver fibrosis, and in hepatic stellate cells in culture. CTGF immunostaining was observed in most human liver biopsies with significant fibrosis. An increase of CTGF immunostaining was associated with a higher score of fibrosis both in the group of chronic hepatitis C (chi(2) = 9.3; P <.01) and in the non-hepatitis C group (chi(2) = 7.2; P <.02). In situ hybridization showed CTGF mRNA expression in spindle cells in both the fibrous septa and sinusoidal lining. In experimental models of liver fibrosis, CTGF accumulated in parallel with the development of septal fibrosis and cirrhosis. Quantification of CTGF mRNA by a real-time reverse-transcription polymerase chain reaction (RT-PCR) assay showed a significant increase of CTGF mRNA in both CCl(4)-induced and bile duct-ligated rat models of liver fibrosis. Expression of CTGF protein and mRNA was definitively assigned to hepatic stellate cells, because CTGF was detected by Western blot both in lysate and supernatant of a hepatic stellate cell line derived from rats. These cells also displayed CTGF protein and mRNA as shown by immunohistochemistry and in situ hybridization. In conclusion, this study shows that CTGF is strongly expressed during liver fibrogenesis, and hepatic stellate cells seem to be the major cellular sources of CTGF in the liver.

A short amino-acid sequence in MH1 domain is responsible for functional differences between Smad2 and Smad3.

Smad proteins are essential components of the signalling cascade initiated by members of the Transforming Growth Factor-beta family. TGFbeta binding to heteromeric complexes of transmembrane Ser/Thr kinases induces Smad2 and Smad3 phosphorylation on their C terminus residues. This phosphorylation leads to oligomerization with Smad4, a common mediator of TGF-beta, activin and BMP signalling. The Smad complexes then translocate to the nucleus where they play transcription regulator roles. Even if they share 92% identity, the two TGFbeta/ restricted Smad2 and Smad3 are not functionally equivalent. As we have previously shown, Smad3 acts as a transcription factor by binding to a TGFbeta-responsive sequence termed CAGA box whereas Smad2 does not. Smad2 differs from Smad3 mainly in the N-terminal MH1 domain where it contains two additional stretches of amino acids that are lacking in Smad3. Here, we show that one of these domains corresponding to exon 3 is responsible for the absence of Smad2 transcriptional activity in CAGA box-containing promoters. Furthermore, in vitro studies indicate that this domain prevents Smad2 from binding to this DNA sequence. This suggests that Smad2 and Smad3 may have different subsets of target genes participating thus in distinct responses among TGFbeta pleiotropic effects.

Induction of micronuclei in vitro by organochlorine compounds in beluga whale skin fibroblasts.

Beluga whales (Delphinapterus leucas) inhabiting the St. Lawrence estuary are highly contaminated with environmental pollutants and have a high incidence of cancer. Environmental contaminants may be partly responsible for the high cancer incidence observed in this population. DNA damage plays an important role in the development of cancer. The micronuclei (MN) assay was used to test the genotoxic potential of organochlorine (OC) pesticides with and without external metabolic factor in skin fibroblasts of an Arctic beluga whale. Toxaphene, chlordane and p,p'-DDT induced significant (p<0. 05) concentration-response increases of micronucleated cells (MNCs). Statistically significant increases in MNCs, ranging from 1.7- to 5-folds when compared to control cultures, were observed for 0.05, 0. 5, 5 and 10 microg/ml toxaphene, 2, 5 and 10 microg/ml chlordane and 10 and 15 microg/ml p,p'-DDT. Presence of exogeneous metabolic factor (S9) completely abolished the MN induction potency of chlordane and p,p'-DDT, and toxaphene induced MN formation at higher concentrations (0.5 microg/ml) than without S9 mix. The ecotoxicological significance of MN induction by low concentrations of toxaphene is unknown and do not imply that toxaphene is involved in the etiology of cancer in St. Lawrence beluga whales. However, because of the known genotoxicity of toxaphene and the long lifespan of beluga whales, it cannot be excluded that toxaphene may pose a long-term genetic hazard to the more contaminated whales of this population.

Direct binding of Smad3 and Smad4 to critical TGF beta-inducible elements in the promoter of human plasminogen activator inhibitor-type 1 gene.

Smad proteins play a key role in the intracellular signalling of transforming growth factor beta (TGF beta), which elicits a large variety of cellular responses. Upon TGF beta receptor activation, Smad2 and Smad3 become phosphorylated and form heteromeric complexes with Smad4. These complexes translocate to the nucleus where they control expression of target genes. However, the mechanism by which Smads mediate transcriptional regulation is largely unknown. Human plasminogen activator inhibitor-1 (PAI-1) is a gene that is potently induced by TGF beta. Here we report the identification of Smad3/Smad4 binding sequences, termed CAGA boxes, within the promoter of the human PAI-1 gene. The CAGA boxes confer TGF beta and activin, but not bone morphogenetic protein (BMP) stimulation to a heterologous promoter reporter construct. Importantly, mutation of the three CAGA boxes present in the PAI-1 promoter was found to abolish TGF beta responsiveness. Thus, CAGA elements are essential and sufficient for the induction by TGF beta. In addition, TGFbeta induces the binding of a Smad3/Smad4-containing nuclear complex to CAGA boxes. Furthermore, bacterially expressed Smad3 and Smad4 proteins, but not Smad1 nor Smad2 protein, bind directly to this sequence in vitro. The presence of this box in TGF beta-responsive regions of several other genes suggests that this may be a widely used motif in TGF beta-regulated transcription.

Characterization of a new human liver myofibroblast cell line: transcriptional regulation of plasminogen activator inhibitor type I by transforming growth factor beta 1.

Myofibroblasts (MF) are a major effector cell type in liver fibrogenesis, where they are thought to derive from the activation of hepatic stellate cells. Cultured human MF, grown from liver explants, retain most of the in vivo characteristics of liver MF but are in limited supply. A continuous MF cell line would therefore be valuable in studying human liver fibrogenesis. For this purpose, we sought to immortalize human liver MF with polyoma virus large T antigen. MF were obtained from explants of human liver and transfected with a plasmid containing the coding sequence of polyoma virus large T antigen. This procedure yielded an activity growing cell line, designated GREF-X, which did not express large T antigen. Nevertheless, this cell line has been passaged repeatedly for almost 1 year and is thus likely immortalized. The morphology of GREF-X resembles that of primary liver MF. These cells have a doubling time of approximately 72 hours and are density-inhibited, and their growth is serum-dependent. Moreover, GREF-X cells do not grow in soft agar or induce tumors in nude mice, suggesting that they are not transformed. They stain positively for MF markers, such as smooth muscle alpha-actin and vimentin; express collagens type I, IV, V, and VI, fibronectin, and laminin: and secrete matrix-metalloproteinase-2. In addition, GREF-X cells are able to take up and esterify [3H]retinol, suggesting that they actually derive from hepatic stellate cells. Finally, these cells respond to transforming growth factor-beta 1, a major mediator of liver fibrogenesis, by increasing secretion of fibronectin and plasminogen activator-inhibitor type 1. Transient transfection experiments showed that plasminogen activator-inhibitor type 1 regulation, by transforming growth factor-beta 1, was transcriptional. We believe, therefore, that GREF-X would be a useful tool for studying the pathophysiology and pharmacology of liver fibrogenesis.

Functional interference between the Spi-1/PU.1 oncoprotein and steroid hormone or vitamin receptors.

The Spi-1/PU.1 protein is an Ets-related transcription factor, whose overexpression is a consequence of SFFV integration in Friend erythroleukemic cells. We present evidence that Spi-1/PU.1 can specifically repress the glucocorticoid-induced activation of promoters carrying a glucocorticoid response element (GRE). Conversely, the glucocorticoid receptor (GR) represses Spi-1/PU.1-mediated transcriptional activation in the presence of hormone. Spi-1/PU.1 also antagonized activation by other nuclear receptors, such as the thyroid hormone or the retinoic acid receptors, in several cell lines, including K562 erythroleukemic cells. These observations suggest that accumulation of the Spi-1/PU.1 protein may interfere with the action of hormones in the erythrocyte differentiation pathway.

Ergonomics aspects of tree-planting using 'multipot' technology.

The highlights of a descriptive study on the ergonomics and occupational health and safety aspects of tree-planting in Québec are presented. The study was planned to consider the most representative geographical sites, planting technologies, and planting organizations. Semi-directed interviews were made with a mixed group of 48 male and female tree-planters and physiological measurements were made on four male planters. Tools and other equipment were also examined. An analysis of the work identified the main elements of the planting cycle, and the high cardiac rate in the working planters was related more to his manual transportation of seedlings and travel on rough paths than to planting per se. A tree-planter will typically travel 2.4 km carrying 16.8 kg of material and equipment in order to plant an average of 1245 seedlings daily. One out of two interviewed planters reported having a work-related accident or incident during his or her lifetime planting career. The body parts reported most frequently injured were the lower extremities (knee, foot, ankle), the skin, the eyes, and the wrist. Recommendations on the development of appropriate tools and footwear for tree-planters and for further research on repetitive strain injury induced by tree-planting have been made.

[Work loss and depression. Impact of fluoxetine]. / Arrêt de travail et dépression. Impact de la fluoxétine.

The goal of our study was to explore the impact of various antidepressant drugs on the relative risk of work loss in depressed patients. 1,852 depressed patients (DSM III-R) were observed using a "cross-sectional" design. Patients were included into five groups: patients without antidepressant treatment, patients treated with one of the main antidepressant drugs in France (amineptine amitriptyline, clomipramine and fluoxetine). Primary variables were the depression intensity (Hamilton scores) and job status (work loss). The other parameters (clinical, demographic, economic, therapeutic) were used as potentially predicting variables. Data have been collected through a network of 295 physicians (GP, Psychiatrists). The main socio-demographic characteristics of treated and untreated depressive patients, either working or absent from work, were predominantly female and city dwellers. A significant difference was found between working patients and work loss in terms of professional characteristics, i.e. type of employment (p < 0.001), type of employer (p < 0.05), level of responsibility (p < 0.01) and type of remuneration (p < 0.01). We found a positive correlation between depression severity and the risk of work loss (R2 = 0.86, p < 0.001). This risk was significantly lower with fluoxetine compared to other treatments. Pooling these data with data from clinical trials led to a saving of 2.4 days (vs clomipramine) to 4.7 days (vs amitriptyline) (p < 0.05, respectively) of work loss per patient for a 8-week treatment period.

Electrical stimulation-induced changes in skeletal muscle enzymes of men and women.

The purpose of the present study was to determine the effects of low-frequency electrical stimulation (LFES) on the skeletal muscle metabolic profile of men and women. The knee extensor muscles of sedentary men (N = 16) and women (N = 10) were submitted to 3 h.d-1 of 8-Hz neuromuscular electrical stimulation with the use of a portable stimulator (Respond II, Medtronic), 6 d.wk-1 for 6 wk. Enzyme activity levels of creatine kinase (CK), hexokinase (HK), glyceraldehydephosphate dehydrogenase (GAPDH), 3-hydroxyacyl CoA dehydrogenase (HADH), citrate synthase (CS), phosphofructokinase (PFK), and cytochrome c oxidase (COX) were determined in vastus lateralis muscle samples taken before and after the LFES protocol. The analyses of variance revealed no change in CK and in GAPDH. However, a small decrease in PFK activity, the rate-limiting enzyme of glycolysis, was observed in female (8%) and in male subjects (10%), but it reached significance in males only (P < 0.05). The activity level of HK, a regulatory enzyme of the skeletal muscle glucose phosphorylation (HK), increased significantly in female subjects only (36%; P < 0.01) in response to the stimulation protocol. Activity level of marker enzymes of the Krebs cycle (CS) and of the electron-transfert chain (COX) significantly increased in males (18% and 16%; P < 0.05) as well as in females (31% and 19%; P < 0.05). Increment in the marker enzyme activity of the fatty acid oxidation (HADH) was significant in female subjects (30%; P < 0.01) and, although significant, rather modest in male subjects (12%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Medico-economic assessment of neuroleptics in schizophrenia. Amisulpride versus haloperidol]. / Evaluation médico-économomique des neuroleptiques dans la schizophrénie. Amisulpride versus halopéridol.

The aim of this study is to assess the economic impact of neuroleptic strategies in the long-term treatment of schizophrenic patients. In this respect a new neuroleptic strategy (amisulpride) was compared to a reference drug (haloperidol) using a cost minimization method. Clinical, demographic and economic (direct medical costs) data were obtained retrospectively from patients' charts. Patients (n = 160) were randomly selected according to diagnosis (schizophrenia, DSM III-R), treatment (outpatient, amisulpride or haloperidol) and follow up period (at least 6 months). The health insurance point of view was selected for the economic analysis. We found a significant reduction of the annual number of days of relapse when patients were treated with amisulpride compared to haloperidol. This reduction was associated with a significant reduction of direct costs mainly related to shorter length of hospitalization. This result was only partly explained by demographic and clinical variables such as the severity of the disease. The differences remained significant when populations were matched. This finding illustrates the validity of the concept of efficiency in psychiatry.

Structural analysis of the human papillomavirus type 16-E2 transactivator with antipeptide antibodies reveals a high mobility region linking the transactivation and the DNA-binding domains.

In order to probe the structure of the transcription factor encoded by the E2 Open Reading Frame of papillomaviruses, we raised polyclonal antibodies against a series of synthetic peptides that cover the HPV16-E2 protein. In gel shift experiments with the native form of the protein, we detected supershifts (caused by the binding of antibodies to the E2-DNA complex) with antibodies synthesized against peptides covering a central region 50 residues long in the E2 protein. On the contrary, antibodies raised against peptides from the NH2- and COOH-termini did not give any supershifted band. Western blot experiments showed that several of these non reacting antibodies did however interact with the denatured protein. These results suggest that the central region that connects the NH2-terminal domain responsible for transcriptional activation and the COOH-domain involved in DNA-binding is exposed and maintained in a conformation resembling the peptide, indicating a high mobility region. In contrast, the DNA-binding and transactivation domains were not recognized by the antipeptide antibodies, in line with secondary structure predictions and sequence comparisons indicating that the E2 protein consists of structured and conserved NH2 and COOH-terminal regions separated by a non-conserved and unstructured region. This flexible 'hinge' region may facilitate contacts between E2 dimers at distance in mechanisms of transcriptional activation steps that involve homosynergy or DNA-looping.

The papillomavirus E2 protein: a factor with many talents.

The products of the papillomavirus E2 open reading frame play a key role in the regulation of the viral cycle. E2 proteins can activate or repress viral promoters by several distinct mechanisms and viral DNA replication requires the expression of the full-length E2 protein together with the product of the E1 open reading frame. This is an interesting example of how a single eukaryotic DNA-binding protein has evolved to perform several different functions and it provides a valuable model system for studying the regulation of eukaryotic transcription and DNA replication.

Two DNA-bound E2 dimers are required for strong transcriptional activation and for cooperation with cellular factors in most cells.

The E2 transcriptional activator encoded by papillomaviruses binds as a dimer to the palindromic sequence ACCGNNNNCGGT present in several copies in the viral genomes. We show that strong activation requires that a minimum of two E2 binding sites are actually occupied by the protein. Studies with constructs bearing two E2 sites separated by variable lengths of DNA showed that there is no stereospecific constraint for E2 homosynergy. The capacity of E2 to cooperate with cellular factors interacting with the promoter/enhancer sequences of the genomes of human papilloma virus types 16, 18, or 33 was further investigated. In epithelial cells, one E2 dimer could not cooperate with the AP1 complex, the glucocorticoid receptor, or the NF1/K factor, whereas several E2 dimers could. These results lead to the notion of the "functional E2 tetramer" as the unit for strong transcriptional activation by E2 and for cooperativity with other cellular factors in this process. Finally, our results suggest that activators such as E2 or the glucocorticoid receptor may interact with partially different targets in the transcriptional machinery.