Papers by Lorraine Chalifour
Metabolites, 2021
Crosstalk between the gut microbiome and the host plays an important role in animal development a... more Crosstalk between the gut microbiome and the host plays an important role in animal development and health. Small compounds are key mediators in this host–gut microbiome dialogue. For instance, tryptophan metabolites, generated by biotransformation of tryptophan through complex host–microbiome co-metabolism can trigger immune, metabolic, and neuronal effects at local and distant sites. However, the origin of tryptophan metabolites and the underlying tryptophan metabolic pathway(s) are not well characterized in the current literature. A large number of the microbial contributors of tryptophan metabolism remain unknown, and there is a growing interest in predicting tryptophan metabolites for a given microbiome. Here, we introduce TrpNet, a comprehensive database and analytics platform dedicated to tryptophan metabolism within the context of host (human and mouse) and gut microbiome interactions. TrpNet contains data on tryptophan metabolism involving 130 reactions, 108 metabolites and...
Journal of Biological Chemistry, 2001
Sodium butyrate induced cell cycle arrest in mammalian cells through an increase in p21 Waf1/Cip1... more Sodium butyrate induced cell cycle arrest in mammalian cells through an increase in p21 Waf1/Cip1 , although another study showed that this arrest is related to pRB signaling. We isolated variants of HeLa cells adapted to growth in 5 mM butyrate. One of these variants, clone 5.1, constitutively expressed elevated levels of p21 Waf1/Cip1 when incubated in regular growth medium and in the presence of butyrate. Despite this elevated level of p21 Waf1/Cip1 , the cells continue to proliferate, albeit at a slower rate than parental HeLa cells. Western blot analyses showed that other cell cycle regulatory proteins were not up-regulated to compensate for the elevated expression of p21 Waf1/Cip1. However, cyclin D1 was downregulated by butyrate in HeLa cells but not in clone 5.1. We conclude that continued expression of cyclin D1 allowed clone 5.1 to grow in the presence of butyrate and elevated levels of p21 Waf1/Cip1 .
Journal of Virology, 1986
Simian virus 40 (SV40) large- and small-tumor antigens (T-Ag, t-Ag) are normally synthesized earl... more Simian virus 40 (SV40) large- and small-tumor antigens (T-Ag, t-Ag) are normally synthesized early after infection of either permissive (monkey) or nonpermissive (mouse) fibroblasts, whereas an equivalent amount of viral coat protein (V-Ag) is observed late after infection of permissive cells and only after viral DNA replication has occurred. To determine whether or not expression of these genes is regulated in the same manner during early mammalian development, SV40 DNA was injected into the nuclei of mouse oocytes and one- and two-cell embryos. In oocytes, about three times more V-Ag was produced than T-Ag, and both were synthesized concomitantly in the same cells. Viral mRNA and proteins synthesized in oocytes comigrated during gel electrophoresis with the same products synthesized in SV40-infected monkey cells. Viral gene expression required circular DNA molecules injected into the nuclei of transcriptionally and translationally active cells. Injected DNA was stable and underwen...
American Journal of Physiology-Heart and Circulatory Physiology, 1999
Differential display identified that gene fragment HA220 homologous to the transcriptional activa... more Differential display identified that gene fragment HA220 homologous to the transcriptional activator factor II 250 (TAFII250) gene, or CCG1, was increased in hypertrophied rodent heart. To determine whether TAFII250 gene expression is modified after cardiac damage, we measured TAFII250 expression in vivo in mouse hearts after injection of the cardiotoxic agent doxorubicin (DXR) and in vitro in DXR-treated isolated rat neonatal cardiomyocytes. In vivo atrial natriuretic factor (ANF), β-myosin heavy chain (β-MHC), Egr-1, and TAFII250 expression increased with dose and time after a single DXR injection, but only ANF and β-MHC expression were increased after multiple injections. After DXR treatment of neonatal cardiomyocytes we found decreased ANF, α-MHC, Egr-1, and TAFII250 expression. Expression of the TAFII250-regulated genes, the D-type cyclins, was increased after a single injection in adult mice and was decreased in DXR-treated cardiomyocytes. Thus expression of Erg-1, TAFII250, a...
American Journal of Physiology-Heart and Circulatory Physiology, 2000
Unmanipulated early growth response-1 (Egr-1)-deficient −/− mice have similar heart-to-body weigh... more Unmanipulated early growth response-1 (Egr-1)-deficient −/− mice have similar heart-to-body weight ratios but express lower amounts of atrial natriuretic factor (ANF), β-myosin heavy chain (β-MHC), skeletal actin, NGF1-A binding protein (NAB)-2, Sp1, c- fos, c- jun, GATA-4, and Nkx2.5 than +/+ or +/− mice. α-MHC, tubulin, and NAB-1 expression was similar. Isoproterenol (Iso) and phenylephrine (PE) infusion into +/+ and −/− mice increased heart weight, ANF, β-MHC, skeletal actin, Sp1, NAB-2, c- fos, and c- jun expression, but induction in −/− mice was lower. Only Iso + PE-treated +/+ mice showed induction of NAB-1, GATA-4, and Nkx2.5. Foci of fibrosis were found in Iso + PE-treated −/− and +/+ mice. Surprisingly, vehicle-treated −/− mice displayed fibrosis and increased Sp1, skeletal actin, Nkx2.5, and GATA-4 expression without hypertrophy. Minipump removal caused the agonist-treated hearts and gene expression to regress to control or near-control levels. Thus Egr-1 deficiency caused...
The Journal of Immunology, 2018
Ischemic myocardial injury results in sterile cardiac inflammation that leads to tissue repair, t... more Ischemic myocardial injury results in sterile cardiac inflammation that leads to tissue repair, two processes controlled by mononuclear phagocytes. Despite global burden of cardiovascular diseases, we do not understand the functional contribution to pathogenesis of specific cardiac mononuclear phagocyte lineages, in particular dendritic cells. To address this limitation, we used detailed lineage tracing and genetic studies to identify bona fide murine and human CD103 + conventional dendritic cell (cDC)1s, CD11b + cDC2s, and plasmacytoid DCs (pDCs) in the heart of normal mice and immunocompromised NSG mice reconstituted with human CD34 + cells, respectively. After myocardial infarction (MI), the specific depletion of cDCs, but not pDCs, improved cardiac function and prevented adverse cardiac remodeling. Our results showed that fractional shortening measured after MI was not influenced by the absence of pDCs. Interestingly, however, depletion of cDCs significantly improved reduction in fractional shortening. Moreover, fibrosis and cell areas were reduced in infarcted zones. This correlated with reduced numbers of cardiac macrophages, neutrophils, and T cells, indicating a blunted inflammatory response. Accordingly, mRNA levels of proinflammatory cytokines IL-1b and IFN-g were reduced. Collectively, our results demonstrate the unequivocal pathological role of cDCs following MI.
Toxicological Sciences, 2018
The authors certify that all research involving human subjects was done under full compliance wit... more The authors certify that all research involving human subjects was done under full compliance with all government policies and the Helsinki Declaration.
Frontiers in Aging Neuroscience, 2017
This study provides evidence for the potential involvement of a novel Egr-1-agrin pathway in syna... more This study provides evidence for the potential involvement of a novel Egr-1-agrin pathway in synaptic homeostatic and compensatory mechanisms at the NMJ. Synaptic homeostasis is greatly affected by the process of aging. These and other data suggest that changes in Egr-1 expression may directly or indirectly promote age-related pathologies.
Journal of Neurochemistry, 2017
Post-synaptic dendritic spines are structurally composed of actin cytoskeleton, which undergoes d... more Post-synaptic dendritic spines are structurally composed of actin cytoskeleton, which undergoes dynamic morphological changes to accommodate incoming synaptic activity. Drebrin is an actin-binding protein highly expressed in dendritic spines that serves an important role in regulating spine morphology. Functionally, loss of drebrin directly correlates with deficits in learning and memory, as is the case observed in Alzheimer's disease. Despite these findings, the regulatory factor responsible for drebrin loss remains unclear. Here, we show that early growth response-1 (Egr-1), an inducible zinc finger transcription factor, down-regulates drebrin expression. Chromatin immunoprecipitation analyses identified Egr-1 binding sites upstream of the drebrin start site in neuronal cells. Overexpression of Egr-1 in vitro in primary hippocampal neurons or in vivo in homogenates prepared from the hippocampi of an inducible mouse model of Egr-1 show reduced drebrin mRNA and protein levels. Conversely, increased drebrin was detected in hippocampal samples isolated from Egr-1-deficient brain. These data demonstrate that Egr-1 interacts with the drebrin promoter and negatively regulates drebrin expression. Furthermore, immunocytochemical and Golgi staining analyses revealed reduced drebrin protein and dendritic spine density as well as reduced expression of synaptic markers in in vitro hippocampal neurons over-expressing Egr-1 and in vivo inducible mouse model of Egr-1. In contrast, increased drebrin expression correlated with increased dendritic spine density was detected in samples from Egr-1-deficient mice. These data provide evidence that Egr-1 is a novel regulator of drebrin expression, which is linked to changes in dendritic spine density.
Journal of Bone Joint Surgery British Volume, Mar 1, 2010
Developmental and degenerative changes in articular cartilage and intervertebral discs (IVDs) are... more Developmental and degenerative changes in articular cartilage and intervertebral discs (IVDs) are not well understood. Early growth response protein-1 (Egr-1) is a transcription factor induced by stress or injury, mitogens, and differentiation factors. It has been shown to be regulated by various cytokines, growth factors and of more interest by ischemic/hypoxic stress as well as shear stress and mechanical injury. These latter regulators have been linked to the pathogenesis of osteoarthritis. Furthermore, Egr-1 has been shown to regulate the expression of collagens and enzymes affecting the extracellular matrix [1-4]. The aim of this study was to determine whether Egr-1 deficiency affects articular cartilage and IVDs. Materials and Methods: Experimental animals-Experimental studies used 6to 7-month-old adult female wild-type (+/+) C57Bl/6 or Egr-1-deficient (−/−) mice. Egr-1 −/− mice have a C57Bl/6 genetic background. All animals were sacrificed at the same age interval (8-to 9-months). Mice were immediately frozen and stored at-20 o C. Histological preparation and staining-Prior to dissection, posterior-anterior and lateral X-rays of whole mice were done. The mice were then dissected carefully, removing the right knee joint and cervical to lumbar spine. These specimens were immediately placed in neutral-buffered 10% formalin. These fixed samples were then decalcified, dehydrated, embedded in paraffin and cut into 4 μm sections. One section from each specimen was stained with the following: hematoxylin-eosin (H&E), Safranin-O/Fast green, and Weigert's hematoxylin/alcian blue/picrosirius red. The slides were examined under light microscopy and digital pictures were taken for appropriate comparison. Bone mineral density (BMD)-Mice were sacrificed and imaged using a PIXImus Bone Densitometer System #56069 (GE Lunar corporation), which measures bone densitometry using dual-energy x-ray absorptiometry. The femur and lumbar vertebrae were selected and analyzed using a Windows 98 Based Software. Micro computed tomography (CT)-Micro CT data were acquired on a SkyScan T1072 X-ray Microscope-Microtomograph (Skyscan, Aartselaar, Belgium). CTan Software (from SkyScan) was used to analyze the sample. Results: We observed that the knee joints of Egr-1 knockout mice were significantly different than that of the wild type. Particularly, the smooth contour of cartilage found on the wild type was more irregular and degenerative in the Egr-1-/mice (Fig 1). Furthermore, a lower concentration of proteoglycans (predominantly aggrecan) was observed in articular cartilage of Egr-1-/-mice as evidenced by reduced staining of Safranin-O. The IVD of Egr-1-/-mice showed evident changes from the wild type. Notably, the nucleus pulposus (NP) showed signs of degeneration and a loss of notochordal cells. The overall disc height was also reduced in the Egr-1-/-mice. In addition, the endplates of Egr-1-/-mice had a greater number of cells than those of WT animals. Furthermore, there was a trend for increased lumbar vertebrae BMD as well a significant increase in BMD in the femur (15% P= 0.09) in the Egr-1-/-mice. The relative bone volume (BV/TV) was significantly smaller in Egr-1-/-mice as was trabecular number (Tb.N) and trabecular separation (Tb.Sp) while there was increased bone surface to bone volume (BS/BV).
Molecular and Cellular Biology, 1985
Circular, double-stranded DNA molecules were injected into nuclei of mouse oocytes and one- or tw... more Circular, double-stranded DNA molecules were injected into nuclei of mouse oocytes and one- or two-cell embryos to determine whether specific sequences were required to replicate DNA during mouse development. Although all of the injected DNAs were stable, replication of plasmid pML-1 DNA was not detected unless it contained either polyomavirus (PyV) or simian virus 40 (SV40) DNA sequences. Replication occurred in embryos, but not in oocytes. PyV DNA, either alone or recombined with pML-1, underwent multiple rounds of replication to produce superhelical and relaxed circular monomers after injection into one- or two-cell embryos. SV40 DNA also replicated, but only 3% as well as PyV DNA. Coinjection of PyV DNA with either pML-1 or SV40 had no effect on the replicating properties of the three DNAs. These results are consistent with a requirement for specific cis-acting sequences to replicate DNA in mammalian embryos, in contrast to sequence-independent replication of DNA injected into X...
Atherosclerosis, Jan 24, 2015
Strategies to reduce LDL-cholesterol involve reductions in cholesterol synthesis or absorption. W... more Strategies to reduce LDL-cholesterol involve reductions in cholesterol synthesis or absorption. We identified a familial hypercholesterolemia patient with an exceptional response to the cholesterol absorption inhibitor, ezetimibe. Niemann-Pick C 1-like 1 (NPC1L1) is the molecular target of ezetimibe. Sequencing identified nucleotide changes predicted to change amino acids 52 (L52P), 300 (I300T) and 489 (S489G) in exceptional NPC1L1. In silico analyses identified increased stability and cholesterol binding affinity in L52P-NPC1L1 versus WT-NPC1L1. HEK293 cells overexpressing WT-NPC1L1 or NPC1L1 harboring amino acid changes singly or in combination (Comb-NPC1L1) had reduced cholesterol uptake in Comb-NPC1L1 when ezetimibe was present. Cholesterol uptake was reduced by ezetimibe in L52P-NPC1L1, I300T-NPC1L1, but increased in S489G-NPC1L1 overexpressing cells. Immunolocalization studies found preferential plasma membrane localization of mutant NPC1L1 independent of ezetimibe. Flotillin ...
Toxicology Reports, 2015
The increased pericardial fat which often accompanies overall obesity is thought to alter cardiac... more The increased pericardial fat which often accompanies overall obesity is thought to alter cardiac structure/function and increase the risk for atrial fibrillation. We hypothesized that chronic exposure to bisphenol A (BPA) would induce pericardial fat, cardiac hypertrophy or arrhythmia. C57bl/6n dams were exposed to BPA (25 ng/ml drinking water) beginning on gestation day 11 and progeny continued on 2.5 ng BPA/ml drinking water. The progeny of control dams (VEH) and dams treated with diethylstilbestrol (DES, 1 g/kg/day, gestation days 11-14) had tap water. After weaning progeny were fed either a control (CD) or high fat diet (HFD) for 3 months. Pericardial fat was present in CD-BPA and CD-DES and not CD-VEH mice, and was increased in all HFD mice. Catecholamine challenge revealed no differences in males, but BPA-exposed females had longer P-wave and QRS complex duration. Only CD-BPA and CD-DES females developed cardiac hypertrophy which was independent of increased blood pressure. Calcium homeostasis protein expression changes in HFD-BPA and HFD-DES mice predict reduced SERCA2 activity in males and increased SERCA2 activity in females. Thus, chronic BPA exposure induced pericardial fat in the absence of HFD, and female-specific changes in cardiac hypertrophy development and cardiac electrical conduction after a catecholamine challenge.
Toxicological Sciences, 2015
Estrogenic compounds such as bisphenol A (BPA) leach from plastics into food and beverage contain... more Estrogenic compounds such as bisphenol A (BPA) leach from plastics into food and beverage containers. Increased BPA exposure has been correlated with increased cardiovascular disease. To test the hypothesis that increased BPA exposure reduces cardiovascular remodeling, we chronically exposed C57bl/6n male mice to BPA and performed a myocardial infarction (MI). We measured cardiac function, as well as myeloid and cardiac fibroblast accumulation and activity. We found increased early death as well as increased cardiac dilation and reduced cardiac function in surviving BPA-exposed mice. Matrix metalloproteinase-2 (MMP2) protein and activity were increased 1.5-fold in BPA-exposed heart. BPA-exposed mice had similar neutrophil infiltration; however, monocyte and macrophage (MU) infiltration into the ischemic area was 5-fold greater than VEH mice potentially due to a 2-fold increase in monocyte chemoattractant protein-1. Monocyte and MU exposure to BPA in vitro in primary bone marrow cultures or in isolated peritoneal MU increased polarization to an activated MU, increased MMP2 and MMP9 expression 2-fold and activity 3-fold, and increased uptake of microspheres 3-fold. Cardiac fibroblasts (CF) differentiate to a-smooth muscle actin (aSMA) expressing myofibroblasts, migrate to the ischemic area and secrete collagen to strengthen the scar. Collagen and aSMA expression were reduced 50% in BPA-exposed hearts. Chronic in vivo or continuous in vitro BPA exposure ablated transforming growth factor beta-mediated differentiation of CF, reduced aSMA expression 50% and reduced migration 40% yet increased secreted MMP2 activity 2-fold. We conclude that chronic BPA exposure reduces the ability to successfully remodel after an MI by increasing MU-based inflammation and reducing myofibroblast repair function.
The open orthopaedics journal, 2008
Doxorubicin (DOX) is widely used in combination cocktails for treatment of childhood hematologica... more Doxorubicin (DOX) is widely used in combination cocktails for treatment of childhood hematological cancers and solid tumors. A major factor limiting DOX usage is DOX-induced cardiotoxicity. However, it is not known whether protectants like dexrazoxane (DXR) and amifostine (AMF) can prevent DOX-mediated bone damage. The present study investigated whether administration of AMF alone or in combination with DXR would prevent any DOX-mediated bone damage. Male rat pups were treated with DOX, DXR, AMF, and their combinations. On neonate day 38, the bone mineral density (BMD), bone mineral content (BMC) and the micro-architecture of the lumbar vertebrae were analyzed. We have shown that when male rats are treated with DOX, DXR, DOX+DXR, AMF, DOX+AMF or DOX+DXR+AMF, there is a decrease in lumbar vertebral BMD (p<0.05). Furthermore, the relative bone volume (BV/TV) was decreased by DXR, DOX+DXR, and DOX+AMF treatments. Interestingly, DOX+AMF significantly increased BV/TV when compared to ...
Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 1993
Previously, we isolated a single line of transgenic mice which develop an enlarged heart due to t... more Previously, we isolated a single line of transgenic mice which develop an enlarged heart due to the expression of the immortalizing gene, polyomavirus large T antigen. Immortal cell lines were isolated from adult transgenic but not from nontransgenic hearts. All of the 24 cell lines expressed vimentin and fibronectin but not desmin or myosin heavy chain. We conclude that the cell lines are of non-muscle origin. Six cell lines were chosen for further study. All six cell lines demonstrate profound morphological and biochemical effects when incubated with 10(-4) M to 10(-7) M retinoic acid. The retinoic acid-treated cell lines showed arrested cellular proliferation and aligned to form rows and vesicle-like structures. Cycloheximide inhibited these retinoic acid-induced changes, indicating a need for continued protein synthesis. Retinoic acid-treated, but not untreated, cells lost expression of vimentin and fibronectin, gained the ability to incorporate acetylated low density lipoprotei...
Toxicology Reports, 2014
Fetal/neonatal exposure to the endocrine disruptor bisphenol A (BPA) has induced obesity and incr... more Fetal/neonatal exposure to the endocrine disruptor bisphenol A (BPA) has induced obesity and increased glucose intolerance. We hypothesized that chronic BPA exposure would worsen the obesity and glucose intolerance induced by a high fat diet (HFD). The drinking water of C57bl/6n dams was treated with vehicle (VEH) or BPA (25 ng/ml) from gestation day 11.5 to postnatal day 21. Another group was treated with oral diethylstilbestrol (DES, 1 g/kg/day) during gestation. Progeny were treated with VEH (VEH and DES groups) or BPA (2.5 ng/ml) in the drinking water and fed either a control diet (CD) or HFD from weaning until euthanasia at 4 months of age. CD-fed mice were similar in size; however HFD-BPA males and HFD-DES mice were smaller than HFD-VEH mice. No CD-fed mice were glucose intolerant. All HFD-fed mice were glucose intolerant. Cholesterol and triglyceride were increased in HFD-VEH mice and HFD-BPA males. Total fat weight and adipocyte area were similar in HFD-VEH and HFD-BPA mice and reduced in HFD-DES mice. HFD-BPA females increased perirenal and reduced gonadal fat weights. Reduced leptin and increased IL-6 in CD-BPA and CD-DES mice were not found in their HFD-cohorts. Adiponectin levels were similar. Thus, although chronic BPA exposure did not increase body size or increase glucose intolerance, it induced an adipokine imbalance in CD-fed mice and sex-specifically altered the lipid response and adipose deposition when fed the HFD.
Toxicology and Applied Pharmacology, 2013
Pregnant women, and thus their fetuses, are exposed to many endocrine disruptor compounds (EDCs).... more Pregnant women, and thus their fetuses, are exposed to many endocrine disruptor compounds (EDCs). Fetal cardiomyocytes express sex hormone receptors making them potentially susceptible to re-programming by estrogenizing EDCs. Diethylstilbestrol (DES) is a proto-typical, non-steroidal estrogen. We hypothesized that changes in adult cardiac structure/function after gestational exposure to the test compound DES would be a proof in principle for the possibility of estrogenizing environmental EDCs to also alter the fetal heart. Vehicle (peanut oil) or DES (0.1, 1.0 and 10.0μg/kg/da.) was orally delivered to pregnant C57bl/6n dams on gestation days 11.5-14.5. At 3months, male progeny were left sedentary or were swim trained for 4weeks. Echocardiography of isoflurane anesthetized mice revealed similar cardiac structure/function in all sedentary mice, but evidence of systolic dysfunction and increased diastolic relaxation after swim training at higher DES doses. The calcium homeostasis proteins, SERCA2a, phospholamban, phospho-serine 16 phospholamban and calsequestrin 2, are important for cardiac contraction and relaxation. Immunoblot analyses of ventricle homogenates showed increased expression of SERCA2a and calsequestrin 2 in DES mice and greater molecular remodeling of these proteins and phospho-serine 16 phospholamban in swim trained DES mice. DES increased cardiac DNA methyltransferase 3a expression and DNA methylation in the CpG island within the calsequestrin 2 promoter in heart. Thus, gestational DES epigenetically altered ventricular DNA, altered cardiac function and expression, and reduced the ability of adult progeny to cardiac remodel when physically challenged. We conclude that gestational exposure to estrogenizing EDCs may impact cardiac structure/function in adult males.
Journal of Biological Chemistry, 2007
The transcription factor Egr-1 activates cyclin-dependent protein kinase 5 (Cdk5) during nerve gr... more The transcription factor Egr-1 activates cyclin-dependent protein kinase 5 (Cdk5) during nerve growth factor (NGF)-induced differentiation of PC12 cells into neurons (Harada, T. Morooka, T., Ogawa, S., and Nishida, E. (2001) Nat. Cell Biol. 3, 453-459). The downstream target of Cdk5 in the Egr-1/Cdk5 pathway is not clear. In this study, we observed that phosphorylation of protein phosphatase 1 (PP1) on Thr 320 is reduced in brain extracts from Egr-1 ؊/؊ mice, indicating that a kinase downstream of Egr-1 phosphorylates PP1. In HEK 293 cells co-transfected with PP1 and Cdk5, Cdk5 phosphorylates PP1. In vitro, Cdk5 purified from bovine brain phosphorylates bacterially expressed recombinant PP1. In NGF-treated PC12 cells, inhibition of Cdk5 by olomoucine or silencing Cdk5 expression by small interfering RNA strategy, suppresses PP1 phosphorylation. Silencing Cdk5 expression by small interfering RNA also blocks NGF-induced neurite outgrowth. Overexpression of PP1 (wild type) promotes NGFinduced differentiation of PC12 cells, whereas that of PP1 (T320A) has no effect. Our data indicate that PP1 is a downstream target of the NGF/Egr-1/Cdk5 pathway during NGFinduced differentiation of PC12 cells and suggest that PP1 phosphorylation promotes neuronal differentiation. Protein phosphatase 1 (PP1) 2 is a major Ser/Thr phosphatase in eukaryotic cells participating in a wide variety of cell functions including cell cycle regulation, muscle contraction, glycogen metabolism, cell differentiation, neural function, and signal transduction (for reviews see Refs. 1-3). PP1 activity is regulated by separate inhibitory and targeting subunits. Inhibitory
Genes & Development, 1987
To determine the requirements for gene expression in mammalian germ cells, circular double-strand... more To determine the requirements for gene expression in mammalian germ cells, circular double-stranded simian virus 40 (SV40) DNA molecules containing deletions in sequences controlling transcription and replication were injected into the nucleus of mouse oocytes. Expression of large (T-Ag) and small (t-Ag) tumor antigens ("early gene products") required at least three GGGCGG boxes, but did not require either the origin of viral DNA replication (ori) or a TATA box. Expression of capsid antigen VP1 ("late gene products") required at least three GGGCGG boxes, sequences between nucleotides 197 and 273 in the 72-bp repeat region, and transactivation by T-Ag. These results are consistent with the requirements for expression of the same genes in differentiated mammalian cells. Surprisingly, however, the 72-bp repeats ("enhancer elements") that are required for expression of T-Ag and t-Ag genes in differentiated cells were not required in mouse oocytes. Similarly...
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Papers by Lorraine Chalifour