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Long-chain polyunsaturated fatty acids (LCPUFA), especially the balance between arachidonic (AA) and docosahexaenoic (DHA) acids are known to have important immunomodulatory roles during the postnatal period when the immune system is rapidly developing. AA and DHA are required in infant formula in many countries but are optional in North America. The rationale for adding these LCPUFA to full-term formula is based on their presence in breast milk and randomized controlled studies that suggest improved cognitive function in preterm infants, but results are more variable in full-term infants. Recently, the European Food Safety Authority has proposed, based on a lack of functional evidence, that AA is not required in infant formula for full-term infants during the first year of life but DHA should remain mandatory. The purpose of this review is to review the evidence from epidemiological and intervention studies regarding the essentiality of AA and DHA in the postnatal infant and maternal diet (breast-feeding) for the immune system development early in life. Although studies support the essentiality of DHA for the immune system development, more research is needed to rule out the essentiality of AA. Nevertheless, intervention studies have demonstrated improvement in many markers of immune function in infants fed formula supplemented with AA and DHA compared with unsupplemented formula, which appears to consistently result in beneficial health outcomes including reduction in the risk of developing allergic and atopic disease early in life.

Background: Lipid-soluble phosphatidylcholine (PC) and aqueous free choline are absorbed and metabolized differently, but the metabolic effects of feeding these 2 forms of choline have not been thoroughly investigated., Objective: We sought to compare the effects of PC and free choline in the maternal diet on the development of the offspring's immune system., Methods: During lactation, Sprague-Dawley dams (n= 10) were randomly assigned to 1 of 2 diet groups containing the same concentration of total choline (1 g/kg diet) as free choline (choline bitartrate) or PC (egg lecithin). The splenocytes of pups aged 21 d were isolated and stimulated ex vivo with concanavalin A (ConA) or lipopolysaccharide (LPS), and the choline concentrations of stomach content, plasma, and the spleen were measured., Results: Pups from PC-fed dams had a lower proportion of cells involved in antigen presentation but produced 54% more interleukin (IL)-2, 163% more IL-6, and 107% more IFN-γ after ConA stimulation and 110% more IL-6 and 43% more tumor necrosis factor (TNF)-α after LPS stimulation (allP< 0.05). The PC concentrations were significantly higher in the plasma and spleen of pups from PC-fed dams (P< 0.05). Increasing the supply of PC in the form of lysophosphatidylcholine to splenocytes in vitro increased the rate of proliferation and IL-2 production and the surface expression of CD25, CD28, CD71, and CD152 on CD8+ T cells, suggesting 1 possible mechanism., Conclusions: The results of this study demonstrate that providing choline to rats in the form of PC (compared to free choline), possibly by increasing the supply of PC to the suckling pups, promotes maturation and improves function of the offspring's immune system., (© 2016 American Society for Nutrition.)

The objective of this study was to determine the effect of feeding a maternal diet supplemented with docosahexaenoic acid (DHA) during the suckling period on the development of the immune system and oral tolerance (OT) in offspring. Dams were randomized to consume one of two nutritionally adequate diets throughout the suckling period: control (N = 12, 0% DHA) or DHA (N = 8, 0.9% DHA) diet. At 11 days, pups from each dam were randomly assigned to a mucosal OT challenge: the placebo or the ovalbumin (OVA) treatment. At three weeks, plasma immunoglobulins and splenocyte cytokine production ex vivo were measured. OVA-tolerized pups had a lower Th2 (IL-13) response to OVA despite the presence of more activated T cells and memory cells (CD27+, all p < 0.05). Feeding a high DHA diet improved the ability of splenocytes to respond to mitogens toward a skewed Th1 response and led to a higher IL-10 and a lower TGF-β production after stimulation with OVA (all p < 0.05). Untolerized DHA-fed pups had lower plasma concentrations of OVA-specific immunoglobulin E (p for interaction < 0.05). Overall, feeding a high DHA maternal diet improves the tolerance response in untolerized suckled pups in a direction that is thought to be beneficial for the establishment of OT.

Choline is a precursor to phosphatidylcholine (PC), a structural molecule in cellular membranes that is crucial for cell growth and function. PC is also required for the secretion of lipoprotein particles from liver and intestine. Choline requirements are increased during lactation when maternal choline is supplied to the offspring through breast milk. To investigate the effect of dietary choline on intestinal lipid metabolism during lactation, choline-supplemented (CS), phosphatidylcholine-supplemented (PCS) or choline-deficient (CD) diets were fed to dams during the suckling period. CD dams had lower plasma triacylglycerol, cholesterol and apoB in the fasted state and following a fat-challenge (P < .05). There was a higher content of neutral lipids and lower content of PC in the intestine of CD dams, compared with CS and PCS fed animals (P < .05). In addition, there was lower (P < .05) villus height in CD dams, which indicated a reduced absorptive surface area in the intestine. Choline is critical for the absorption of fat in lactating rats and choline deficiency alters intestinal morphology and impairs chylomicron secretion by limiting the supply of PC., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Choline demands during lactation are high; however, detailed knowledge is lacking regarding the optimal dietary intake during this critical period. The present study was designed to determine the effects of varying intakes of choline on maternal immune function during lactation. Primiparous Sprague-Dawley rats (n 42) were randomised 24-48 h before birth and fed the following diets for 21 d: choline-devoid (0 g choline/kg diet; D, n 10); 1·0 g choline/kg diet (C1, n 11); 2·5 g choline/kg diet (C2·5, n 10); 6·2 g choline/kg diet (C6, n 11). Splenocytes were isolated and stimulated ex vivo with concanavalin A, lipopolysaccharide (LPS) or CD3/CD28. D and C6 dams had lower final body weight, spleen weight and average pup weight than C1 dams (P< 0·05). There was a linear relationship between free choline concentration in pup stomach contents with maternal dietary choline content (P< 0·001, r² 0·415). Compared with C1 and C2·5, D spleens had a lower proportion of mature T cells and activated suppressor cells, and this resulted in reduced cytokine production after stimulation (P< 0·05). Feeding 6·2 g choline/kg diet resulted in a higher cytokine production after stimulation with CD3/CD28 (P< 0·05). Except for a higher IL-6 production after LPS stimulation with cells from the C2·5 dams (P< 0·05), there were no differences between the C1 and C2·5 dams. For the first time, we show that feeding lactating mothers a diet free of choline has substantial effects on their immune function and on offspring growth. Additionally, excess dietary choline had adverse effects on maternal and offspring body weight but only minimal effects on maternal immune function.

Epidemiological studies identify meat as a major source of choline; however, the most comprehensive reference for food choline content, the United States Department of Agriculture (USDA) database for dietary choline, does not include values for meats of importance in some regions. In this work, the total choline and choline-containing moieties of 20 samples of meat were analyzed by LC-MS/MS; 16 samples analyzed are absent from the USDA database and 4 samples included for comparison. Average total choline for one serving (75 g) was 50 ± 12 mg, which was 82.6% ± 5.5% phosphatidylcholine. There was general agreement between total choline levels in the meats analyzed in this work and USDA values. A strong negative correlation (r = -0.777, p < 0.001) between total choline and fat content was found. This research added choline composition data to a food group that is a major source of choline and ultimately this data will assist in obtaining more accurate estimates of dietary choline.

Despite recommendations for higher choline intakes during pregnancy and lactation, there is limited research regarding maternal intake during these important periods. In the present study, we estimated dietary choline intake during pregnancy and lactation in a population of Albertan women and the contribution of egg and milk consumption to intake. Dietary intake data were collected from the first 600 women enrolled in a prospective cohort study carried out in Alberta, Canada. During the first and/or second trimester, the third trimester and 3 months postpartum, 24 h dietary intake recall data were collected. A database was constructed including foods consumed by the cohort and used to estimate dietary choline intake. The mean total choline intake value during pregnancy was 347 (SD 149) mg/d, with 23% of the participants meeting the adequate intake (AI) recommendation. During lactation, the mean total choline intake value was 346 (SD 151) mg/d, with 10% of the participants meeting the AI recommendation. Phosphatidylcholine was the form of choline consumed in the highest proportion and the main dietary sources of choline were dairy products, eggs and meat. Women who consumed at least one egg in a 24 h period had higher (P< 0·001) total choline intake and were eight times more likely (95% CI 5·2, 12·6) to meet choline intake recommendations compared with those who did not consume eggs during pregnancy. Women who reported consuming ≥ 500 ml of milk in a 24 h period were 2·8 times more likely (95 % CI 1·7, 4·8) to meet daily choline intake recommendations compared with those consuming < 250 ml of milk/d during pregnancy. Choline intake is below the recommendation levels in this population and the promotion of both egg and milk consumption may assist in meeting the daily choline intake recommendations.

Estimating dietary choline intake can be challenging due to missing foods in the current United States Department of Agriculture (USDA) database. The objectives of the study were to quantify the choline-containing moieties and the total choline content of a variety of pulses available in North America and use the expanded compositional database to determine the potential contribution of pulses to dietary choline intake. Commonly consumed pulses (n = 32) were analyzed by hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC LC-MS/MS) and compared to the current USDA database. Cooking was found to reduce the relative percent from free choline and increased the contribution of phosphatidylcholine to total choline for most pulses (P < 0.05). Using the expanded database to estimate choline content of recipes using pulses as meat alternatives, resulted in a different estimation of choline content per serving (±30%), compared to the USDA database. These results suggest that when pulses are a large part of a meal or diet, the use of accurate food composition data should be used.

In this article, we argue that a combined anthropology/neuroscience field of enquiry can make a significant and distinctive contribution to the study of the relationship between culture and the brain. This field, which can appropriately be termed as neuroanthropology, is conceived of as being complementary to and mutually informative with social and cultural neuroscience. We start by providing an introduction to the culture concept in anthropology. We then present a detailed characterization of neuroanthropology and its methods and how they relate to the anthropological understanding of culture. The field is described as a humanistic science, that is, a field of enquiry founded on the perceived epistemological and methodological interdependence of science and the humanities. We also provide examples that illustrate the proposed methodological model for neuroanthropology. We conclude with a discussion about specific contributions the field can make to the study of the culture-brain nexus.

Neuroanthropology is a new field of research that can make two distinctive contributions to our understanding of the brain-culture nexus. The first contribution has to do with the question of how socially shared meanings and practices are reflected in brain function and structure - the culture in the brain problem. Neuroanthropology's second contribution relates to the neural processes that generate socially shared meanings and practices - the brain in culture problem. Research in cultural neuroscience has focused on the first question while research in social neuroscience has a bearing on the second. A neuroanthropological perspective is vital to integrate these two most important dimensions of the human condition. In this paper we review research from cultural anthropology, primatology, and developmental psychology, in addition to social and cultural neuroscience, that deals with these two core neuroanthropological issues. Regarding the brain in culture problem, the review reveals that relational recoding is the basis of a host of cognitive functions that enable the formation of socially shared meanings and practices. The review also shows that relational recoding corresponds to the processing style characteristic of the prefrontal cortex (PFC). With respect to the culture in the brain problem, the most salient finding is the extent and breadth of the influence of culture on the brain: literally all brain areas, cortical and subcortical, respond to regularities in the cultural stream of experience. Furthermore, culture not only shapes preexisting patterns of neural activity but it may also determine whether a pattern is at all present. In addition to influencing brain function culture also changes the structure of the brain. The review finally indicates that cultural regularities can modulate cognitive function both implicitly and explicitly. Overall, the PFC can be regarded as the structure that establishes relationships between things and events that are represented in the different areas distributed across the brain. These areas become in this manner more readily available for modulation or constitution by (cultural) experience. However, the PFC is the structure that stands first to be modified or constituted by cultural experience as it is the structure that lays culture's foundations.

To assess safety and immunogenicity, 213 healthy infants aged 6 weeks to 4 months were randomized to receive a single dose of placebo, a 10(4) or 10(5) p.f.u. dose of rhesus rotavirus (RRV) serotype 3, human-RRV reassortant (VP-7 serotypes 1, 2 or 4) or a 10(4) or 10(5) p.f.u. dose of tetravalent rotavirus vaccine (containing equal parts of serotype 1, 2, 3 and 4 strains). The infants were fed ad libitum before and after vaccination; no buffer was used. For 7 days after vaccination, potential vaccine side effects were monitored, and no significant differences were noted for any symptom evaluated among the single serotype, tetravalent or placebo groups. Sera, obtained before and 28 days after vaccination, were measured for antibody to rotavirus by IgG, IgA and IgM enzyme-linked immunosorbent assay in all subjects, and by neutralizing antibody to the individual serotypes by plaque reduction in placebo and tetravalent vaccinees. The serological response rates for serotypes 1, 2, 3, 4 and the tetravalent vaccine were 25, 12, 19, 11 and 22%, respectively, at 10(4) p.f.u.; 47, 50, 35, 29 and 61%, respectively, at 10(5) p.f.u.; and 37% for placebo. The tetravalent vaccine was more immunogenic at 10(5) than at 10(4) p.f.u. (p = 0.04). Grouped together, the vaccines at 10(5) p.f.u. (single serotype and tetravalent) were more immunogenic than the vaccines at 10(4) p.f.u. (38 of 85 versus 17 of 94 seroresponders; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

As an approach to mapping replicons in an extended chromosomal region, the temporal order of DNA replication was analyzed in the murine major histocompatibility gene complex (MHC). Replicating DNA from T-lymphoma and myelomonocyte cell lines was density labeled with bromodeoxyuridine and extracted from cells which had been fractionated into different stages of S phase by centrifugal elutriation. The replicating DNA from each fraction of S phase was separated from nonreplicating DNA on density gradients, blotted, and hybridized with 34 specific MHC probes. The earliest replication occurred in the vicinity of transcribed genes K, HAM1 and HAM2, RD, B144, D, L, T18, and T3. The temporal order of replication of groups of DNA segments suggests the location of five or six replicons within the H-2 complex, some of which appear to be either unidirectional or markedly asymmetric. The rates of replication through each of these apparent replicons appear to be similar. The TL region of the S49.1 T-lymphoma cells, which contains at least three transcribed genes, replicates earlier than the inactive TL region of WEHI-3 myelomonocytic cells. These results provide further evidence of a relationship between transcription and the initiation of DNA replication in mammalian cells. The mouse MHC examined in this study is the largest chromosomal region (> 2,000 kb) measured for timing of replication to date.

Visna virus is the prototypic member of a subfamily of retroviruses responsible for slow infections of animals and humans. As a part of our investigation of the functions of viral gene products in virus replication, we have isolated three infectious molecular clones and determined the complete nucleotide sequences of two of the clones. We have also characterized the progeny of the biologically cloned viral stocks and of the infectious clones and document considerable heterogeneity in plaque size and antigenic phenotype of the former that is reduced to near homogeneity in the progeny of the infectious clones. It thus should now be possible to trace the emergence of antigenic variants of visna virus as well as ascribe defined functions to structural and regulatory genes of the virus in determining neurovirulence and the slow tempo of infection.

The effect of tritiated thymidine incorporation on DNA replication was studied in Chinese hamster ovary cells. Rapidly eluting (small) DNA from cells labeled with 2 microCi of [3H]thymidine per ml (200 microCi/mmol) for 60 min matured to a large nonelutable size within approximately 2 to 4 h, as measured by the alkaline elution technique. However, DNA from cells exposed to 10 microCi of [3H]thymidine per ml (66 microCi/mmol) was more rapidly eluting initially and did not mature to a nonelutable size during subsequent incubation. Semiconservative DNA replication measured by cesium chloride gradient analysis of bromodeoxyuridine-substituted DNA was also found to be affected by the final specific activity of the [3H]thymidine used in the labeling protocol. Dramatic cell cycle perturbations accompanied these effects on DNA replication, suggesting that labeling protocols commonly used to study DNA metabolism produce aberrant DNA replication and subsequent cell cycle perturbations.

We investigated the nucleotide sequence requirements of the adenovirus 2 late promoter when activated by either a trans-acting regulatory protein or a cis-acting enhancer element. Using deletion mutants in transient expression assays, we determined that the 5' limit of the region required for activation by a trans-acting regulatory protein, the adenovirus early region 1a gene product, and the simian virus 40 enhancer is the same in both 293 and HeLa cells. Surprisingly, the 3' limit of required sequences varied, depending on the mechanism of activation. Activation mediated by the early region 1a protein endogenous in 293 cells or produced after cotransfection of HeLa cells requires the region around the transcriptional start site, whereas activation brought about by an enhancer element in HeLa cells has no requirement for these sequences. Under no conditions tested did the simian virus 40 enhancer activate the late promoter in 293 cells, even when sequences sufficient for enhancer-mediated activation in HeLa cells, but not for early region 1a activation, were present. These results suggest the existence of at least two different mechanisms for positive regulation of promoter activity.

Antibiotic therapy for children without foci of infection and at risk for bacteremia is controversial. A prospective randomized clinical trial was conducted using expectant antibiotic therapy in children at risk for bacteremia. A total of 96 children (aged 6 to 24 months) with temperature of more than 40 degrees C, no identifiable source of infection, and a leukocyte count greater than or equal to 15,000/microL and/or sedimentation rate greater than or equal to 30 were enrolled. The following tests were performed on all children: blood culture, chest roentgenogram, urinalysis, and urine culture. A lumbar puncture was performed if a child was 12 months or less. Patients were randomized to receive either no antibiotic therapy or Bicillin C-R, 50,000 U/kg intramuscularly, followed by penicillin V, 100 mg/kg/d, orally four times a day for three days. Patients were examined at 24 and 72 hours. Fifty patients were treated expectantly and 46 received no antimicrobial therapy. Ten of the 96 patients were bacteremic (nine had Streptococcus pneumoniae, one had Haemophilus influenzae). Four of the five children treated for bacteremia showed improvement at the first follow-up visit (afebrile and no obvious focus of infection). The five untreated patients showed no improvement; four patients developed focal infections (two had meningitis, two had otitis media) (P less than or equal to .05, Fisher exact test). No complications of expectant therapy were detected. Thus, expectant antibiotic therapy for children who have no obvious source of infection and who meet these criteria associated with occult bacteremia is warranted.

We have constructed a frameshift mutation in the simian virus 40 early region using a novel method of oligonucleotide-directed mutagenesis. The mutated DNA specifies an 84,000-dalton large tumor antigen that consists of approximately equal to 75,000 daltons encoded by the wild-type reading frame and 9,000 daltons, by the alternative reading frame (wild-type large tumor antigen is approximately equal to 82,000 daltons). The frameshifted carboxyl terminus of the protein bears a strong similarity to the same region of polyoma virus middle-sized tumor antigen. We have found that the mutant DNA is unable to replicate when introduced into permissive monkey cells and incapable of transforming nonpermissive mouse cells.

We studied the effect of acetazolamide on plasma potassium in normals and in two patients with hyperkalemic periodic paralysis. Administration of acetazolamide for 48 hours lowered mean plasma potassium in normals from 4.01 to 3.56 mEq per liter (p less than 0.001) and in the patients from 4.55 to 4.00 mEq per liter (p less than 0.001). This kaliopenic effect of acetazolamide may account for its therapeutic action in hyperkalemic periodic paralysis.

To study the effects that DNA replication can exert on transcription in mammalian cells, we have analyzed transient expression from the adenovirus major late promoter contained on replicating and nonreplicating plasmids in several cell types. When a 100-bp fragment containing the late promoter was used to direct expression of the simian virus 40 (SV40) early region, efficient transcription could be detected that was only slightly enhanced when a functional origin of replication was included in the plasmid. In contrast with this, and with similar findings using related late promoter-containing plasmids, expression from this promoter was absolutely dependent on DNA replication when it was inserted in the region of SV40 DNA encoding the late mRNA 5' ends and expression was assayed in human HeLa cells and BSC-1 and COS-7 monkey cells. In contrast, transcription was totally independent of replication in human 293 cells. These results, which were not due to differences in template copy number, suggest that both cis- and trans-acting factors can influence a promoter's response to DNA replication and point to possible functional similarities between replication origins and transcriptional enhancers.

We prospectively followed a group of unimmunized, immunosuppressed children with cancer to determine their relative risk of influenza and the severity of infection compared with those of siblings or matched community controls. The incidence of influenza infection was higher in children with cancer (23/73, 32%) than in control subjects (10/70, 14%, p = 0.02). A preseason hemagglutination inhibition titer greater than or equal to 1:32, generally used as a marker of successful immunization in vaccine trials, was protective for all children in the control groups, but did not prevent influenza infection in 24% of the patients with cancer. Infection rates of patients and community controls with titers greater than or equal to 1:32 differed significantly (p = 0.006). No significant differences were noted in duration of reported symptoms between groups, and clinical complications occurred too infrequently to analyze. However, 2 (11%) of 18 of the cancer patients with positive culture results were hospitalized during the illness and one patient developed a nosocomial infection. None of the control children was hospitalized. These findings suggest the need for further study of the immunologic response of immunosuppressed children to influenza infection and a clinical efficacy trial of the influenza vaccine in these patients.

A maize genomic clone containing a zein gene (Z4) was inserted into the T-region of the T37 Ti plasmid. Agrobacterium tumefaciens cells carrying this modified Ti plasmid were used to inoculate sunflower stemlets. Callus tissue active in nopaline synthesis was grown from a single transformed cell. DNA analysis of this tissue showed that the zein gene plus T-DNA was present in approximately 12 copies per diploid sunflower genome. A 1000 +/- 100 base RNA homologous to a zein probe could be isolated from the engineered sunflower tissue and the 5' end of this RNA was determined by S1 nuclease mapping. Two transcription start sites were detected. The positions of these transcription start sites and the ratio of the amounts of the two transcripts are identical for the Z4 gene in sunflower and in maize endosperm. Although the zein RNA isolated from the engineered sunflower tissue could be translated in a wheat germ system to yield an immuno-precipitable protein of the expected mol. wt., the presence of the zein protein in the sunflower tissue could not be demonstrated.

Most eukaryotic messenger RNAs are transcribed as precursor molecules that must be processed by capping, splicing, 3' cleavage, and polyadenylylation to yield mature mRNAs. An important, unresolved issue is whether any of these reactions are linked either to transcription by RNA polymerase II or to each other. To address one aspect of this question, we constructed a chimeric gene containing an RNA polymerase III promoter (the adenovirus VAI promoter) fused to the body and 3'-flanking sequences of a protein-coding gene (the herpesvirus tk gene). Here we show that this hybrid gene was transcribed from the RNA polymerase III promoter following transfection of human 293 cells and that the transcripts produced were stable and efficiently transported to the cytoplasm. Although a significant proportion of the transcripts were prematurely terminated at specific sites within the gene, a high percentage of the full-length RNA was accurately cleaved and polyadenylylated. These results demonstrate that cleavage and polyadenylylation of mRNA precursors are not obligatorily coupled to transcription by RNA polymerase II in vivo.

Zein, the prolamine fraction of maize, is localized in the endosperm in membrane-bound structures called protein bodies, which have polyribosomes on their surfaces. These polysomes or the mRNA fraction isolated from them will direct the synthesis of zein-like proteins in vitro. The in vitro products consist primarily of two molecular weight classes but show considerable charge heterogeneity when analyzed by isoelectric focusing. Although the molecular weight classes are very similar for different inbred lines, the isoelectric focusing patterns differ.Results given here suggest that the extensive charge heterogeneity of zein proteins does not result from the presence of a large number of totally distinct mRNAs. Zein proteins synthesized in vitro fall into several families related by sequence homologies in their mRNAs. In Illinois High Protein (IHP) the major zein mRNAs can be classified into three families based on their binding to cloned complimentary DNA copies of IHP zein mRNA. Each of three other lines we have studied (W22, Oh43, and W64A) has zein mRNAs that are related to those of IHP. Among these four lines the molecular weights of the members of a given family are generally similar, but the number of members in a family and their isoelectric points differ.

Hyperkalemic periodic paralysis is frequently considered a disorder in which episodes of weakness and an attendant rise in plasma potassium interrupt a baseline of normal strength and potassium. We studied venous potassium throughout a 36-hour period in two patients with hyperkalemic periodic paralysis and in nine normals under rigidly controlled conditions. At no time did the patients with periodic paralysis have an attack of weakness, but their mean potassium concentrations were above the normal range for 33 to 36 hours. In hyperkalemic periodic paralysis, the postprandial change in potassium relative to insulin release exceeded normal. There appears to be a continuous alteration in potassium regulation in our patients with hyperkalemic periodic paralysis.

The small DNA tumour virus simian virus 40 (SV40) has served as an excellent model for many studies on the mechanism and control of gene expression in eukaryotic cells. The SV40 early region produces two protein products. One product (large-T antigen) is known both to repress early viral transcription and to stimulate viral replication by binding to specific sites in the origin-promoter region. The early promoter has several similarities to other RNA polymerase II promoters, for example, it possesses a TATA box, an upstream element and an enhancer. However, the SV40 early promoter differs from other known RNA polymerase II promoters in that the origin of viral DNA replication is embedded within it. Here we show that the SV40 early region is expressed at an extremely low level following its introduction ito human 293 cells, contrasting with results observed in a large number of other cells lines. We show further that the lack of expression is due to repression of transcription from the SV40 early promoter by viral DNA replication which occurs efficiently in 293 cells.