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1.
J Dairy Sci ; 99(1): 205-20, 2016 Jan.
Article in English | MEDLINE | ID: mdl-26601586

ABSTRACT

Condensed tannins (CT) may affect ruminal biohydrogenation of dietary polyunsaturated fatty acids. A feeding experiment was conducted with 24 Holstein cows to evaluate whether diets containing CT from different forage legumes can increase polyunsaturated fatty acids, especially n-3 fatty acid content in milk and cheese, without affecting negatively their physicochemical and sensorial properties. Cows were assigned to 4 treatment groups (n=6) for 52 d, divided into 2 periods: a control period (CoP) and an experimental period (ExP). During the CoP, cows received a basal diet composed of hay, corn silage, ExtruLin (Trinova Handel & Marketing AG, Wangen, Switzerland), concentrate, and alfalfa (AF) in a ratio of 45:25:5:7:18. In the ExP, in 3 of the 4 groups AF was replaced by either sainfoin (SF; 19% CT in dry matter) or 1 of 2 cultivars of birdsfoot trefoil [Polom (BP), 3% CT; Bull (BB), 5% CT]. At the end of each period, milk was collected on 3 consecutive days and analyzed for milk gross composition and fatty acid profile and was processed to Gruyère-type cheese. A trained panel assessed the sensory quality of raw milk and cheese using discriminative and descriptive tests. This experimental design consisting of AF in both the CoP and ExP allowed us to quantify effects due to lactation stage and experimental diets. In both the CoP and ExP, dry matter intake and milk yield did not differ among treatment groups. From the CoP to the ExP, milk urea content was reduced by 23% with SF, remained unchanged with BP, and tended to increase with AF and BB. The odor of the raw BB milk was judged to be different from AF milk. With SF, switching from the CoP to the ExP resulted in a 17% increase of the 18:3n-3 proportion in milk and cheese lipids. In BP cheese, the increase was 3%, whereas it tended to decrease in BB cheese. Additionally, the 20:5n-3 and 22:5n-3 proportions tended to increase in SF cheese from the CoP to the ExP. Compared with the AF cheeses, cheeses from cows fed CT-containing legumes were judged harder and tended to be less adhesive to the palate. In addition, SF and BP cheeses had less rind. In conclusion, feeding SF compared with BB and BP increased the content of 18:3n-3 in the milk and the cheese without a negative effect on flavor of the cheese. Despite a similar CT content, the 2 birdsfoot trefoil cultivars had opposite effects on milk urea and 18:3n-3 deposition, suggesting that, besides the content, the chemical structure may have had an important effect on the CT efficacy.


Subject(s)
Cattle/physiology , Cheese/standards , Fatty Acids, Omega-3/analysis , Milk/standards , Proanthocyanidins/analysis , Silage/analysis , Animals , Cheese/analysis , Diet/veterinary , Fabaceae , Fatty Acids/analysis , Fatty Acids, Omega-3/metabolism , Female , Lactation , Medicago sativa , Milk/chemistry , Switzerland , Zea mays
2.
Clin Genet ; 88(6): 584-8, 2015 Dec.
Article in English | MEDLINE | ID: mdl-25582056

ABSTRACT

Myocilin glaucoma is an autosomal dominant disorder leading to irreversible blindness, but early intervention can minimize vision loss and delay disease progression. The purpose of this study was to discuss the benefits of predictive genetic testing in minors for Myocilin mutations associated with childhood onset glaucoma. Three families with Myocilin mutations associated with an age of onset before 18 years and six unaffected at-risk children were identified. Predictive genetic testing was discussed with the parents and offered for at-risk minors. Parents opted for genetic testing in half of the cases. None carried the familial mutation. The age of disease onset in the family, the severity of the condition, and the age of the child are all factors that appear to influence the decision of the parent to test their children. Predictive genetic testing for early onset Myocilin glaucoma can facilitate early detection of disease or discharge from routine ophthalmic examinations.


Subject(s)
Cytoskeletal Proteins/genetics , Eye Proteins/genetics , Genetic Testing/methods , Glaucoma, Open-Angle/genetics , Glycoproteins/genetics , Mutation , Adolescent , Child , Family Health , Female , Glaucoma, Open-Angle/diagnosis , Humans , Male , Pedigree , Predictive Value of Tests , Sequence Analysis, DNA , Visual Field Tests , Young Adult
3.
Leukemia ; 29(2): 423-32, 2015 Feb.
Article in English | MEDLINE | ID: mdl-25027513

ABSTRACT

The leukemogenic CALM-AF10 fusion protein is found in patients with immature acute myeloid and T-lymphoid malignancies. CALM-AF10 leukemias display abnormal H3K79 methylation and increased HOXA cluster gene transcription. Elevated expression of HOXA genes is critical for leukemia maintenance and progression; however, the precise mechanism by which CALM-AF10 alters HOXA gene expression is unclear. We previously determined that CALM contains a CRM1-dependent nuclear export signal (NES), which is both necessary and sufficient for CALM-AF10-mediated leukemogenesis. Here, we find that interaction of CALM-AF10 with the nuclear export receptor CRM1 is necessary for activating HOXA gene expression. We show that CRM1 localizes to HOXA loci where it recruits CALM-AF10, leading to transcriptional and epigenetic activation of HOXA genes. Genetic and pharmacological inhibition of the CALM-CRM1 interaction prevents CALM-AF10 enrichment at HOXA chromatin, resulting in immediate loss of transcription. These results provide a comprehensive mechanism by which the CALM-AF10 translocation activates the critical HOXA cluster genes. Furthermore, this report identifies a novel function of CRM1: the ability to bind chromatin and recruit the NES-containing CALM-AF10 transcription factor.


Subject(s)
Gene Expression Regulation, Leukemic , Homeodomain Proteins/metabolism , Karyopherins/physiology , Oncogene Proteins, Fusion/physiology , Receptors, Cytoplasmic and Nuclear/physiology , Animals , Cell Line, Tumor , Cell Transformation, Neoplastic , Chromatin Immunoprecipitation , Fatty Acids, Unsaturated/chemistry , Fibroblasts/metabolism , Gene Expression Profiling , HEK293 Cells , Humans , Luciferases/metabolism , Mice , Multigene Family , Oncogene Proteins, Fusion/genetics , Transcription, Genetic , U937 Cells , Exportin 1 Protein
5.
Eye (Lond) ; 26(1): 70-9, 2012 Jan.
Article in English | MEDLINE | ID: mdl-21979860

ABSTRACT

PURPOSE: To report outcomes of deep sclerectomy (DS) with intraoperative mitomycin C (MMC) application in eyes with previous failed glaucoma surgery (GS) and/or cataract extraction (CE). PATIENTS AND METHODS: Single-surgeon case series of 82 eyes of 82 patients undergoing DS with MMC. The patients had previous CE with IOL and/or conjunctival GS and treated intraocular pressure (IOP) >18 mm Hg. MMC (0.2 mg/ml) was applied for 2-3 min before scleral flap dissection. Complete success was defined as IOP between 6 and 21 mm Hg or a reduction of 20% from baseline without medications. Reoperation for glaucoma or related complications, or loss of light perception vision was considered as failure. RESULTS: Mean follow-up was 57.7 ± 22.4 months with 78% of patients completing the 3-year follow-up. Mean IOP decreased from 24.0 mm Hg (22.3-25.6, 95% confidence intervals) to 13.4 mm Hg (12.0-14.2) at 3 years after surgery (P<0.001). There was a significant decrease in the number of glaucoma medications from 2.0 ± 1 preoperatively, to 0.3 ± 0.7, 3 years after surgery. Kaplan-Meier cumulative success rates were 85.6% at 1 year, 80.0% at 2 years, and 76% at 3 years. At 3 years, IOP was maintained <19 and 15 mm Hg in 83 and 70% of eyes, respectively. Fourteen eyes (17.1%) had complications. Delayed hypotony (IOP <6 mm Hg) was the commonest complication in five eyes (6.1%). CONCLUSION: DS with MMC appears to be a safe and effective surgical procedure for eyes with previous intraocular surgery.


Subject(s)
Glaucoma/surgery , Intraocular Pressure/drug effects , Mitomycin/therapeutic use , Pseudophakia/surgery , Sclera/surgery , Sclerostomy/methods , Aged , Analysis of Variance , Female , Glaucoma/drug therapy , Glaucoma/physiopathology , Humans , Intraoperative Care/methods , Male , Minimally Invasive Surgical Procedures , Postoperative Complications , Pseudophakia/physiopathology , Reoperation , Retrospective Studies , Sclera/drug effects , Sclera/physiopathology , Trabeculectomy , Visual Acuity
7.
J Dairy Sci ; 92(3): 826-36, 2009 Mar.
Article in English | MEDLINE | ID: mdl-19233775

ABSTRACT

The angiotensin-converting enzyme (ACE) inhibitory activity and the concentration of the 2 ACE-inhibiting tripeptides Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) were studied during cheese ripening in 7 Swiss cheese varieties. The semi-hard cheeses Tilsiter, Appenzeller 1/4 fat, Tête de Moine, and Vacherin fribourgeois and the extra-hard and hard cheeses Berner Hobelkäse, Le Gruyère, and Emmentaler were investigated. Three loaves of each variety manufactured in different cheese factories were purchased at the beginning of commercial ripeness and investigated at constant intervals until the end of the usual sale period. Good agreement was found between ACE-inhibitory activity and the total concentration of VPP and IPP at advanced ripening stages. In most of the investigated varieties ACE-inhibitory activity and the concentration of the 2 tripeptides initially increased during the study period. A decline in the concentration of VPP and IPP was obtained toward the end of the investigated period for Tilsiter and Gruyère. The ratio of VPP/IPP decreased during ripening in all varieties with the exception of Emmentaler. However, large variations were observed among the cheese varieties as well as the individual loaves of the same variety. Chemical characterization of the investigated cheeses revealed that qualitative differences in the proteolysis pattern, not quantitative differences in the degree of proteolysis, are responsible for the observed variations in the concentrations of VPP and IPP. The presence of Lactobacillus helveticus in the starter culture was associated with elevated concentrations of VPP and IPP. The results of the present study show that concentrations of VPP and IPP above 100 mg/kg are attainable in semi-hard cheese varieties after ripening periods of about 4 to 7 mo and that stable concentrations of the 2 antihypertensive tripeptides can be expected over several weeks of cheese ripening.


Subject(s)
Cheese/analysis , Food Handling , Oligopeptides/analysis , Animals , Cheese/classification , Peptidyl-Dipeptidase A , Time Factors
8.
J Dairy Sci ; 91(1): 29-38, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18096922

ABSTRACT

The contents of the 2 antihypertensive peptides Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) were determined in 101 samples from 10 different Swiss cheese varieties using HPLC with subsequent triple mass spectrometry. In the category of extra hard and hard cheeses, the Protected Denomination of Origin cheeses Berner Alpkäse and Berner Hobelkäse, L'Etivaz à rebibes, Le Gruyère, Sbrinz, Emmentaler (organic and conventional) and in the category of semihard cheeses, the varieties Tilsiter, Appenzeller 1/4 fat and full fat, Tête de Moine, and Vacherin fribourgeois were screened in the study. The average concentration of the sum of VPP and IPP in the screened cheese varieties varied to a large extent, and substantial variations were obtained for individual samples within the cheese varieties. The lowest average concentration of the 2 tri-petides was found in L'Etivaz à rebibes (n = 3) at 19.1 mg/kg, whereas Appenzeller 1/4 fat (n = 4) contained the greatest concentration at 182.2 mg/kg. In individual samples, the total concentration of VPP and IPP varied between 1.6 and 424.5 mg/kg. With the exception of a 10-yr-old cheese, VPP was always present at greater concentrations than IPP. Milk pretreatment, cultures, scalding conditions, and ripening time were identified as the key factors influencing the concentration of these 2 naturally occurring bioactive peptides in cheese. The results of the present study show that various traditional cheese varieties contain, on average, similar concentrations of the 2 antihypertensive peptides to the recently developed fermented milk products with blood pressure-lowering property. This may serve as a basis for the development of a functional cheese with blood pressure-lowering property.


Subject(s)
Angiotensin-Converting Enzyme Inhibitors/analysis , Cheese/analysis , Oligopeptides/analysis , Antihypertensive Agents/analysis , Switzerland , Tandem Mass Spectrometry
9.
Pediatr Hematol Oncol ; 24(7): 503-12, 2007.
Article in English | MEDLINE | ID: mdl-17786786

ABSTRACT

The Training Committee (TC) of the American Society of Pediatric Hematology/Oncology created a foundation of common goals and objectives that could provide a structure for fellowship programs. The TC conducted a survey of program directors for input into the structure of their programs and training methods and the results are presented here. Additionally, a suggested core program is outlined, taking into account the new common requirements as stipulated by the ACGME and ABP, and additional suggestions from the program directors. This paper highlights the suggested training objectives and educational opportunities that should be afforded all fellows in this sub-specialty. The goal of this consensus statement is to provide a model curriculum to improve quality and consistency of training and achieve compliance with new requirements while simultaneously recognizing the importance of alternative approaches that emphasize each program's unique strengths and character.


Subject(s)
Curriculum , Education, Medical, Graduate , Hematology/education , Medical Oncology/education , Pediatrics/education , Consensus , Fellowships and Scholarships , Humans , Societies, Medical , Training Support , United States
11.
Vnitr Lek ; 48(9): 856-60, 2002 Sep.
Article in Czech | MEDLINE | ID: mdl-16737124

ABSTRACT

The authors provide evidence of the extreme increase of the frequency of acute pancreatitis. At the First Surgical Clinic in Brno in 1934 the frequency of acute pancreatitis (AP) was 0.2 pro mille (in the course of 3 years 4 patients among 20 000 hospitalized patients), at present (65 years later) in 1999 - 2001 it is 0.7%--74 patients among 10 676 hospitalized patients. This is 35 times more, 48 men (65%) and 26 women (35%). The mean age was 48.6 years, range 26 - 83 years. The lethality of the whole group was 9.5%. From the total number of 74 patients seriously ill patients (Atlanta II classification) 25 patients--34%, Atlanta I--49 patients--66%. 7 patients with acute necrotizing infected pancreatitis died--28% of the whole group. Initial treatment of AP is based on adherence to three principles:(a) intensive treatment, (b) elimination of etiological factors and (c) control of complications. Contrary to other affectios in AP, there is no specific surgical treatment. Indications for surgical treatment of AP: I. early stage--explorative laparotomy if stabilization of patient by adequate treatment to resolve comorbidity (NPB etc.) is impossible, II. advanced stage--evacuation of infected necroses, abscesses, infected or bleeding pseudocyst, elective sanation of biliary tract. The optimal timing is between the 2nd and 3rd week of the disease. Premature surgery does not have a favourable effect on the subsequent course of the disease.


Subject(s)
Pancreatitis/surgery , Acute Disease , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Pancreatitis/classification , Pancreatitis/diagnosis
12.
Prostate ; 47(3): 194-204, 2001 May 15.
Article in English | MEDLINE | ID: mdl-11351349

ABSTRACT

BACKGROUND: Mxi1, an antagonist of c-Myc, maps to human chromosome 10q24-q25, a region altered in a substantial fraction of prostate tumors. Mice deficient for Mxi1 exhibit significant prostate hyperplasia. We studied the ability of Mxi1 to act as a growth suppressor in prostate tumor cells. METHODS: We infected DU145 prostate carcinoma cells with an Mxi1-expressing adenovirus (AdMxi1) in vitro, and measured Mxi1 expression, cell proliferation, soft agar colony formation, and cell cycle distribution. To explore mechanisms of Mxi1-induced growth arrest, we performed gene expression analysis. RESULTS: AdMxi1 infection resulted in reduced cell proliferation, reduced soft agar colony formation, and a higher proportion of cells in the G(2)/M phase of the cell cycle. This G(2)/M growth arrest was associated with elevated levels of cyclin B, and reduced levels of c-MYC and MDM2. CONCLUSIONS: The ability of AdMxi1 to suppress prostate tumor cell proliferation supports a role for Mxi1 loss in the pathogenesis of a subset of human prostate cancers. Prostate 47:194-204, 2001.


Subject(s)
DNA-Binding Proteins/physiology , Prostatic Neoplasms/pathology , Transcription Factors/physiology , Adenoviridae/genetics , Basic Helix-Loop-Helix Transcription Factors , Blotting, Western , Cell Division/physiology , DNA-Binding Proteins/biosynthesis , DNA-Binding Proteins/genetics , Flow Cytometry , G2 Phase/physiology , Gene Expression Profiling , Humans , Male , Microscopy, Confocal , Mitosis/physiology , Prostatic Neoplasms/genetics , Prostatic Neoplasms/metabolism , Proto-Oncogene Proteins c-myc/antagonists & inhibitors , Transcription Factors/biosynthesis , Transcription Factors/genetics , Tumor Cells, Cultured , Tumor Suppressor Proteins
13.
J Biol Chem ; 274(40): 28794-802, 1999 Oct 01.
Article in English | MEDLINE | ID: mdl-10497252

ABSTRACT

MXI1, a member of the MAD family of Myc antagonists, encodes a transcription factor whose expression must be tightly regulated to maintain normal cell growth and differentiation. To more closely investigate the transcriptional regulation of the human MXI1 gene, we have cloned and characterized the MXI1 promoter. After clarification of the 5'- and 3'-untranslated regions of the cDNA (indicating that the true length of the MXI1 transcript is 2643 base pairs), we identified two transcription initiation sites. We subsequently isolated the MXI1 promoter, which is GC-rich and lacks a TATA box. Although it contains at least six potential initiator sequences, functional studies indicate the proximal two initiator sequences in combination with nearby Sp1 and MED-1 sites together account for virtually all promoter activity. We also demonstrate that MXI1 promoter activity is repressed by high levels of AP2. These studies provide further insight into the complex regulatory mechanisms governing MXI1 gene expression and its role in cellular differentiation and tumor suppression.


Subject(s)
DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation, Developmental , Sp1 Transcription Factor/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , 3' Untranslated Regions , 5' Untranslated Regions , Base Sequence , Basic Helix-Loop-Helix Transcription Factors , DNA , Endodeoxyribonucleases/metabolism , Humans , K562 Cells , Molecular Sequence Data , Mutation , Promoter Regions, Genetic , Regulatory Sequences, Nucleic Acid , Transcription Factor AP-2 , Tumor Suppressor Proteins
14.
Cancer Res ; 57(21): 4905-12, 1997 Nov 01.
Article in English | MEDLINE | ID: mdl-9354456

ABSTRACT

The Mxi1 protein functions in a regulatory network with members of the c-Myc family, in which c-Myc activates transcription and stimulates cell proliferation, and Mxi1 negatively regulates these actions. Inactivation of the MXI1 gene could, therefore, inhibit differentiation and enhance proliferation in the presence of normal levels of c-Myc, and thus MXI1 is a potential tumor suppressor gene. We and others have previously mapped the MXI1 gene to the distal portion of chromosome 10q, a region that is rearranged or affected by allelic loss in many astrocytic brain tumors. Using a newly described polymorphic CA microsatellite repeat in the third MXI1 intron, we show that 7 of 11 informative glioblastomas demonstrated MXI1 allelic loss. Sequence analysis revealed no somatic mutations in any of the six MXI1 coding exons, similar to findings in prostate tumors with MXI1 allelic loss. To determine whether MXI1 can indeed function as a suppressor of growth, we have introduced a steroid-inducible MXI1 expression vector into the U87MG cell line, a glioblastoma cell line lacking endogenous MXI1 expression. Induction of MXI1 expression resulted in a decreased growth rate and distinct morphological changes. Furthermore, cell cycle analysis demonstrated that induction of MXI1 results in accumulation of cells in the G2-M phase. Thus, these studies support the notion that MXI1 normally functions to suppress cell growth and suggest that loss of MXI1 function may play a role in human glioblastoma development.


Subject(s)
DNA-Binding Proteins/metabolism , Gene Deletion , Genes, Tumor Suppressor/physiology , Glioblastoma/genetics , Transcription Factors/metabolism , Basic Helix-Loop-Helix Transcription Factors , Cell Division/genetics , Chromosomes, Human, Pair 10/genetics , DNA-Binding Proteins/drug effects , DNA-Binding Proteins/genetics , Dexamethasone/pharmacology , G2 Phase/genetics , Genetic Vectors/drug effects , Genetic Vectors/genetics , Glioblastoma/pathology , Glucocorticoids/pharmacology , Humans , Transcription Factors/drug effects , Transcription Factors/genetics , Transfection , Tumor Suppressor Proteins
15.
Cathet Cardiovasc Diagn ; 39(3): 287-90, 1996 Nov.
Article in English | MEDLINE | ID: mdl-8933975

ABSTRACT

We describe the development of hemolysis from moderate residual shunting across a patent ductus arteriosus following coil embolization. The fall in hemoglobin levels from 11.6 to 6.0 gm/dl necessitated a second coil procedure which resulted in complete closure of the residual shunting and resolution of hemolysis. Therefore, appearance of anemia following coil embolization of patent ductus arteriosus should be monitored closely; however, repeat coil embolization with elimination of residual shunt will lead to prompt recovery of normal hemoglobin levels.


Subject(s)
Ductus Arteriosus, Patent/therapy , Embolization, Therapeutic/adverse effects , Hemolysis , Anemia, Hemolytic/etiology , Ductus Arteriosus, Patent/complications , Female , Humans , Infant
16.
Genomics ; 32(3): 466-70, 1996 Mar 15.
Article in English | MEDLINE | ID: mdl-8838813

ABSTRACT

MXI1, a member of the MYC family of transcription factors, is thought to negatively regulate MYC function and may therefore be a potential tumor suppressor gene. Using detailed restriction mapping and partial DNA sequencing analysis, we have determined the genomic organization of the human MXI1 gene to facilitate a search for mutations that affect MXI1 function. The gene spans a region of approximately 60 kb on chromosome 10q24-q25 and comprises six exons. The correspondence of these exons to previously identified Mxi1 functional domains suggests that alternatively spliced transcripts may regulate Mxi1 functional activity. The presence of a cryptic ATG start codon in exon 2 suggests that a functional protein missing the SIN3-interacting domain (exon 1) may be generated by alternative splicing. Finally, we have identified two polymorphic regions within the MXI1 locus: a polymorphic CA repeat in the third intron and an AAAAC polymorphism in the noncoding region of exon 6. These findings will facilitate the analysis of tumors for the presence of inactivating mutations in MXI1 coding and regulatory sequences.


Subject(s)
DNA-Binding Proteins/genetics , Genes, Tumor Suppressor/genetics , Restriction Mapping , Transcription Factors/genetics , Alternative Splicing , Amino Acid Sequence , Basic Helix-Loop-Helix Transcription Factors , Chromosomes, Human, Pair 10 , Cloning, Molecular , Exons/genetics , Humans , Introns/genetics , Polymorphism, Genetic , Sequence Analysis, DNA , Tumor Suppressor Proteins
18.
Pediatr Neurol ; 10(4): 309-12, 1994 Jun.
Article in English | MEDLINE | ID: mdl-8068157

ABSTRACT

A 20-month-old infant with Turner syndrome presented with opsoclonus-myoclonus and tonic pupils in association with an abdominal neuroblastoma. Despite complete removal of the tumor, the child developed progressive hearing loss, areflexia, and seizures. Immunohistochemical and Western blot studies of serum and cerebrospinal fluid revealed the presence of anti-Hu antineuronal antibody, which cross-reacted with areas of the patient's tumor. Treatment with intravenous immunoglobulin coincided with the resolution of opsoclonus-myoclonus and the cessation of new neurologic symptoms. This case provides direct support for the autoimmune basis of paraneoplastic symptoms associated with neuroblastoma and suggests that treatment with intravenous immunoglobulin may be of value.


Subject(s)
Antigens, Neoplasm/immunology , Autoantibodies/analysis , Neuroblastoma/immunology , Paraneoplastic Syndromes/immunology , Abdominal Neoplasms/immunology , Antibodies, Antinuclear/immunology , Autoantibodies/blood , Autoantibodies/cerebrospinal fluid , Blotting, Western , Female , Humans , Immunoglobulins, Intravenous/therapeutic use , Infant , Myoclonus/immunology , Myoclonus/therapy , Neurons/immunology , Nystagmus, Pathologic/immunology , Paraneoplastic Syndromes/therapy
20.
Mol Cell Biol ; 14(6): 4097-107, 1994 Jun.
Article in English | MEDLINE | ID: mdl-8196648

ABSTRACT

The ability of a transcription factor to function in vivo must be determined in part by its ability to bind to its recognition site in chromatin. We have used Max and derivatives of c-Myc to characterize the effect of changes of dimerization partner on binding to nucleosomal DNA templates. We find that homo- and heterodimeric complexes of these proteins bind to the CACGTG sequence in free DNA with similar affinities. Although Max homodimers bind to nucleosomes, truncated c-Myc homodimers do not. Surprisingly, modifying the c-Myc dimerization interface or changing its dimerization partner to Max enables nucleosomal DNA binding. Thus, changes in dimer structure or dimerization efficiency can have significant effects on nucleosome binding that are not predicted from their affinity for free DNA. We conclude that domains other than the basic region per se influence the ability of a transcription factor to bind to nucleosomal DNA and that changes of dimerization partner can directly affect the ability of a factor to occupy nucleosomal binding sites.


Subject(s)
DNA-Binding Proteins/metabolism , DNA/metabolism , Nucleosomes/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Transcription Factors/metabolism , Base Sequence , Basic-Leucine Zipper Transcription Factors , Binding Sites , Chromatography, Affinity , DNA/isolation & purification , DNA Probes , DNA-Binding Proteins/isolation & purification , Deoxyribonuclease I , Electrophoresis, Polyacrylamide Gel , Kinetics , Macromolecular Substances , Molecular Sequence Data , Oligonucleotide Probes , Proto-Oncogene Proteins c-myc/isolation & purification , Recombinant Fusion Proteins/isolation & purification , Recombinant Fusion Proteins/metabolism
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