Transcriptional repression by wild-type p53 utilizes histone deacetylases, mediated by interaction with mSin3a

There is growing evidence that the p53 tumor suppressor protein not only can function to activate gene transcription but also to repress the expression of specific genes. Although recent studies have implicated the transcriptional repression function of p53 in the pathway of apoptosis, the molecular basis of this activity remains poorly understood. This study takes a first step toward elucidating this mechanism. We report that trichostatin A (TSA), an inhibitor of histone deacetylases (HDACs), abrogates the ability of p53 to repress the transcription of two genes that it negatively regulates, Map4 and stathmin. Consistent with this finding, we report that p53 physically associates in vivo with HDACs. This interaction is not direct but, rather, is mediated by the corepressor mSin3a. Both wild-type p53 and mSin3a, but not mutant p53, can be found bound to the Map4 promoter at times when this promoter preferentially associates with deacetylated histones in vivo. Significantly, inhibition of p53-mediated transcriptional repression with TSA markedly inhibits apoptosis induction by p53. These data offer the first mechanistic insights for p53-mediated transcriptional repression and underscore the importance of this activity for apoptosis induction by this protein.

A subset of tumor-derived mutant forms of p53 down-regulate p63 and p73 through a direct interaction with the p53 core domain

The p53 protein is related by sequence homology and function to the products of two other genes, p63 and p73, that each encode several isoforms. We and others have discovered previously that certain tumor-derived mutants of p53 can associate and inhibit transcriptional activation by the alpha and beta isoforms of p73. In this study we have extended these observations to show that in transfected cells a number of mutant p53 proteins could bind and down-regulate several isoforms not only of p73 (p73 alpha, -beta, -gamma, and -delta) but also of p63 (p63 alpha and -gamma; Delta Np63 alpha and -gamma). Moreover, a correlation existed between the efficiency of p53 binding and the inhibition of p63 or p73 function. We also found that wild-type p63 and p73 interact efficiently with each other when coexpressed in mammalian cells. The interaction between p53 mutants and p63 or p73 was confirmed in a physiological setting by examining tumor cell lines that endogenously express these proteins. We also demonstrated that purified p53 and p73 proteins interact directly and that the p53 core domain, but not the tetramerization domain, mediates this interaction. Using a monoclonal antibody (PAb240) that recognizes an epitope within the core domain of a subset of p53 mutants, we found a correlation between the ability of p53 proteins to be immunoprecipitated by this antibody and their ability to interact with p73 or p63 in vitro and in transfected cells. Based on these results and those of others, we propose that interactions between the members of the p53 family are likely to be widespread and may account in some cases for the ability of tumor-derived p53 mutants to promote tumorigenesis.

Cloning of the putative tumour suppressor gene for hereditary multiple exostoses (EXT1)

Hereditary multiple exostoses is an autosomal dominant disorder that is characterized by short stature and multiple, benign bone tumours. In a majority of families, the genetic defect (EXT1) is linked to the Langer-Giedion syndrome chromosomal region in 8q24.1. From this region we have cloned and characterized a cDNA which spans chromosomal breakpoints previously identified in two multiple exostoses patients. Furthermore, the gene harbours frameshift mutations in affected members of two EXT1 families. The cDNA has a coding region of 2,238 bp with no apparent homology to other known gene sequences and thus its function remains elusive. However, recent studies in sporadic and exostosis-derived chondrosarcomas suggest that the 8q24.1-encoded EXT1 gene may have tumour suppressor function.

Pulmonary tuberculosis: CT findings--early active disease and sequential change with antituberculous therapy

To evaluate findings of active pulmonary tuberculosis on computed tomographic (CT) scans and their sequential changes before and after antituberculous chemotherapy, 29 patients with newly diagnosed pulmonary tuberculosis and 12 patients with recent reactivation were studied prospectively. The diagnosis of active pulmonary tuberculosis was based on positive acid-fast bacilli in sputum (n = 29) and changes on serial radiographs obtained during treatment (n = 12). Twenty-six patients were followed up with CT during treatment for 1-20 months. Lungs from the cadavers of nine other patients, who died of pulmonary tuberculosis, were studied to provide a pathologic basis for diagnosis. At examination with CT, centrilobular lesions (nodules or branching linear structures 2-4 mm in diameter) were most commonly seen (n = 39 [95%]); in the 26 patients with follow-up, most of these lesions disappeared within 5 months after the start of treatment. In 11 of 12 patients with recent reactivation, CT clearly differentiated old fibrotic lesions from new active lesions. Lesions in and around the small airways appear to be the most characteristic CT feature of early active tuberculosis and may be a reliable criterion for disease activity.

Information storage and retrieval through quantum phase

Information was stored as quantum phase in an N-state Rydberg atom data register. One or more flipped states stored in an eight-state atomic wave packet could be retrieved in a single operation, in agreement with a recent proposal by Grover.

Myristoylated alanine-rich C kinase substrate (MARCKS) produces reversible inhibition of phospholipase C by sequestering phosphatidylinositol 4,5-bisphosphate in lateral domains

The myristoylated alanine-rich protein kinase C substrate (MARCKS) is a major protein kinase C (PKC) substrate in many different cell types. MARCKS is bound to the plasma membrane, and several recent studies suggest that this binding requires both hydrophobic insertion of its myristate chain into the bilayer and electrostatic interaction of its cluster of basic residues with acidic lipids. Phosphorylation of MARCKS by PKC introduces negative charges into the basic cluster, reducing its electrostatic interaction with acidic lipids and producing translocation of MARCKS from membrane to cytoplasm. The present study shows that physiological concentrations of MARCKS (<10 microM) inhibit phospholipase C (PLC)-catalyzed hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) in phospholipid vesicles. A peptide corresponding to the basic cluster, MARCKS(151-175), produces a similar inhibition, which was observed with both PLC-delta1 and -beta1. Direct fluorescence microscopy observations demonstrate that the MARCKS peptide forms lateral domains enriched in the acidic lipids phosphatidylserine and PIP2 but not PLC, which accounts for the observed inhibition of PIP2 hydrolysis. Phosphorylation of MARCKS(151-175) by PKC releases the inhibition and allows PLC to produce a burst of inositol 1,4, 5-trisphosphate and diacylglycerol.

Low vitamin D status is associated with physical inactivity, obesity and low vitamin D intake in a large US sample of healthy middle-aged men and women

The aim of this study was to investigate modifiable predictors of vitamin D status in healthy individuals, aged 55-74, and living across the USA. Vitamin D status [serum 25-hydroxyvitamin D (25(OH)D)] was measured along with age and season at blood collection, demographics, anthropometry, physical activity (PA), diet, and other lifestyle factors in 1357 male and 1264 female controls selected from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort. Multivariate linear and logistic regression analyses were used to identify associations with vitamin D status. Three%, 29% and 79% of the population had serum 25(OH)D levels<25, <50 and <80 nmol/L, respectively. The major modifiable predictors of low vitamin D status were low vitamin D dietary and supplement intake, body mass index (BMI) >30 kg/m2, physical inactivity (PA) and low milk and calcium supplement intake. In men, 25(OH)D was determined more by milk intake on cereal and in women, by vitamin D and calcium supplement and menopausal hormone therapy (MHT) use. Thus targeting an increase in vigorous activity and vitamin D and calcium intake and decreasing obesity could be public health interventions independent of sun exposure to improve vitamin D status in middle-aged Americans.

Solid organ transplantation from hepatitis B virus-positive donors: consensus guidelines for recipient management

Use of organs from donors testing positive for hepatitis B virus (HBV) may safely expand the donor pool. The American Society of Transplantation convened a multidisciplinary expert panel that reviewed the existing literature and developed consensus recommendations for recipient management following the use of organs from HBV positive donors. Transmission risk is highest with liver donors and significantly lower with non-liver (kidney and thoracic) donors. Antiviral prophylaxis significantly reduces the rate of transmission to liver recipients from isolated HBV core antibody positive (anti-HBc+) donors. Organs from anti-HBc+ donors should be considered for all adult transplant candidates after an individualized assessment of the risks and benefits and appropriate patient consent. Indefinite antiviral prophylaxis is recommended in liver recipients with no immunity or vaccine immunity but not in liver recipients with natural immunity. Antiviral prophylaxis may be considered for up to 1 year in susceptible non-liver recipients but is not recommended in immune non-liver recipients. Although no longer the treatment of choice in patients with chronic HBV, lamivudine remains the most cost-effective choice for prophylaxis in this setting. Hepatitis B immunoglobulin is not recommended.

Regulation of senescence associated signaling mechanisms in chondrocytes for cartilage tissue regeneration

Adult articular chondrocytes undergo slow senescence and dedifferentiation during in vitro expansion, restricting successful cartilage regeneration. A complete understanding of the molecular signaling pathways involved in the senescence and dedifferentiation of chondrocytes is essential in order to better characterize chondrocytes for cartilage tissue engineering applications. During expansion, cell fate is determined by the change in expression of various genes in response to aspects of the microenvironment, including oxidative stress, mechanical stress, and unsuitable culture conditions. Rapid senescence or dedifferentiation not only results in the loss of the chondrocytic phenotype but also enhances production of inflammatory mediators and matrix-degrading enzymes. This review focuses on the two groups of genes that play direct and indirect roles in the induction of senescence and dedifferentiation. Numerous degenerative signaling pathways associated with these genes have been reported. Upregulation of the genes interleukin 1 beta (IL-1β), p53, p16, p21, and p38 mitogen-activated protein kinase (MAPK) is responsible for the direct induction of senescence, whereas downregulation of the genes transforming growth factor-beta (TGF-β), bone morphogenetic protein-2 (BMP-2), SRY (sex determining region Y)-box 9 (SOX9), and insulin-like growth factor-1 (IGF-1), indirectly induces senescence. In senescent and dedifferentiated chondrocytes, it was found that TGF-β, BMP-2, SOX9, and IGF-1 are downregulated, while the levels of IL-1β, p53, p16, p21, and p38 MAPK are upregulated followed by inhibition of the normal molecular functioning of the chondrocytes. This review helps to elucidate the underlying mechanism in degenerative cartilage disease, which may help to improve cartilage tissue regeneration techniques.

Outcome of the modified Broström procedure for chronic lateral ankle instability using suture anchors

The modified Broström procedure is an anatomic reconstruction of the lateral ankle ligaments. The present study evaluated twenty-two patients (mean age = 27.2 years) with chronic lateral ankle instability who underwent surgical repair of their lateral ankle ligaments using suture anchors as part of the modified Broström procedure. All surgeries were performed by the senior author (AK) on an outpatient basis. At a mean follow-up of 34.5 months (minimum of 18 months), twenty patients (91%) reported a good or excellent functional outcome as assessed by the Karlsson and Peterson ankle function scoring scale. One patient developed a superficial wound infection post-operatively that was eradicated with a course of oral antibiotics. Sixteen of the twenty-two patients were available for follow-up physical examination and stress radiographs. Fourteen of the sixteen patients had no evidence of instability on physical examination or on stress radiographs. One patient had diminished sensation in the superficial peroneal nerve distribution. Five of the sixteen patients had generalized ligamentous laxity; none of these patients had an excellent result, and they had lower "Overall Satisfaction" scores (P=0.013). We conclude that the use of suture anchors is a simple and effective adaptation of the modified Broström procedure, which results in a good or excellent outcome in the majority of patients with few complications.

Impact of transrenal aortic endograft placement on endovascular graft repair of abdominal aortic aneurysms

PURPOSE

Successful endovascular repair of an abdominal aortic aneurysm (AAA) requires the creation of a hemostatic seal between the endograft and the underlying aortic wall. A short infrarenal aortic neck may be responsible for incomplete aneurysm exclusion and procedural failure. Sixteen patients who had an endograft positioned completely below the lowest renal artery and 37 patients in whom a porous portion of an endograft attachment system was deliberately placed across the renal arteries were studied to identify if endograft positioning could impact on the occurrence of incomplete aneurysm exclusion.

METHODS

Fifty-three patients underwent aortic grafting constructed from a Palmaz balloon expandable stent and an expandable polytetrafluoroethylene (ePTFE) graft implanted in an aorto-ilio-femoral, femoral-femoral configuration. Arteriography, duplex ultrasonography and spiral CT scans were performed in each patient before and after endografting to evaluate for technical success, the presence of endoleaks, and renal artery perfusion.

RESULTS

There was no statistically significant difference in patient demography, AAA size, or aortic neck length or diameter between patients who had their endografts placed below or across the renal arteries. However, significantly more proximal aortic endoleaks occurred in those patients with infrarenal endografts (P < or = .05). Median serum creatinine level before and after endografting was not significantly different between the 2 patient subgroups, with the exception of 2 patients who had inadvertent coverage of a single renal orifice by the endograft. Median blood pressure and the requirement for antihypertensive therapy remained the same after transrenal aortic stent grafting. Significant renal artery compromise did not occur after appropriately positioned transrenal stents as shown by means of angiography, CT scanning, and duplex ultrasound scan. Mean follow-up time was 10.3 months (range, 3 to 18 months). Patients who had significant renal artery stenosis (> or =50%) before aortic endografting did not show progression of renal artery stenosis after trans-renal endografting. Two patients with transrenal aortic stent grafts had inadvertent coverage of 1 renal artery by the endograft because of device malpositioning, which resulted in nondialysis dependent renal insufficiency. In addition, evidence of segmental renal artery infarction (<20% of the kidney), which did not result in an apparent change in renal function, was shown by means of follow-up CT scans in 2 patients with transrenal endografts.

CONCLUSION

Transrenal aortic endograft fixation using a balloon expandable device in patients with AAAs can result in a significant reduction in the risk of proximal endoleaks. Absolute attention to precise device positioning, coupled with the use of detailed imaging techniques, should reduce the risk of inadvertent renal artery occlusion from malpositioning. Long-term follow-up is essential to determine if there will be late sequelae of transrenal fixation of endografts, which could adversely effect renal perfusion.

Outpatient uterine artery embolization for symptomatic uterine fibroids: experience in 49 patients

PURPOSE

To assess the feasibility of performing uterine artery embolization as an outpatient treatment for symptomatic uterine fibroids.

MATERIALS AND METHODS

Forty-nine consecutive patients (mean age, 44.5 years; range, 28-54 years) underwent uterine artery embolization during a 12-month period. Embolization was performed with 350-500 microm polyvinyl alcohol particles (44 of 49) or Gelfoam pledgets (five of 49). At discharge, patients were given instructions regarding the constitutional symptoms to expect after embolization. A specific medication regimen consisting of prochlorperazine, ketorolac, meperidine, and hydrocodone was prescribed for relief of these symptoms. All patients were telephoned within 24 hours of discharge. During long-term follow-up, a questionnaire was administered to all patients to evaluate the periprocedural experience. Three-month clinical follow-up was available in 26 patients and 6-month imaging follow-up was available in 16 patients.

RESULTS

Fourteen patients presented with menorrhagia, six had bulk-related symptoms (abdominal distension, stress incontinence, pelvic pain), and 29 had both. Technical success for bilateral embolization was 98%. Forty-seven of 49 patients were discharged to home 6-8 hours after the procedure; two patients required overnight observation in an ambulatory unit (one because of postprocedure hypertension and one because of a late procedure completion time). At the first follow-up phone call, reported symptoms included pelvic pain/cramping in 83.7% (41 of 49), fatigue in 75.5% (37 of 49), nausea/vomiting in 46.9% (23 of 49), and a nonpurulent vaginal discharge in 18.4% (nine of 49). These symptoms were satisfactorily controlled with discharge medications in 48 of 49 patients. No patients returned to the hospital or visited an emergency room during the first 48 hours after discharge. Forty-six of 49 patients were satisfied with the decision for home discharge. The average uterine volume reduction in 16 patients with 6-month imaging follow-up was 47.5%; 88.5%, of patients (23 of 26) with 3-month clinical follow-up reported improvement or elimination of symptoms.

CONCLUSION

With defined telephone follow-up, staff availability, and a protocol designed to alleviate the postprocedure constitutional symptoms, uterine artery embolization is both safe and effective when performed as an outpatient procedure.

DNA polymerase beta: pre-steady-state kinetic analysis and roles of arginine-283 in catalysis and fidelity

DNA polymerase beta (pol beta) is the smallest and least complex DNA polymerase. The structure of the enzyme is well understood, but little is known about its catalytic properties, particularly processivity and fidelity. Pre-steady-state analysis of the incorporation of a single nucleotide into a short 25/45 oligonucleotide primer-template by pol beta was used to define the kinetic parameters of the polymerase. In addition, nucleotide analogs and site-specific mutants, along with structural analyses, were used to probe the structure-function relationship of pol beta. Several significant findings have been obtained: (i) The catalysis by pol beta is processive and displays an initial burst under pre-steady-state conditions, but the processivity is poor compared to other polymerases. (ii) The fidelity of pol beta is also low relative to other polymerases. (iii) Under pre-steady-state conditions the chemical step appears to be only partially rate-limiting on the basis of the low thio effect (4.3), defined as kpol(dNTP)/kpol(dNTP alpha S). The thio effect increases to 9 for incorporation of an incorrect nucleotide. These results are consistent with the existence of a substrate-induced conformational change that is also partially rate-limiting. (iv) A comparison between the two-dimensional NMR spectra of the wild-type and mutant enzymes indicates that the mutations at position 283 did not significantly perturb the structure of the enzyme. The conformational stability of the mutants is also unperturbed. Thus, R283 is not important to the overall structure of the enzyme. (v) The results of kinetic analyses of R283A and R283K mutants indicate that the hydrogen bond between R283 of pol beta and the template is important for catalysis. Both R283A and R283K mutants displayed decreases in catalytic efficiency by a factor of ca. 200 relative to wild-type pol beta. The mutants are also less faithful by a factor of 2-4, in terms of the T-G mispair vs the T-A correct pair. The perturbation, however, could occur at both the implied conformational step and the chemical step, since the thio effects of the mutants for both correct and incorrect nucleotides are similar to those of WT pol beta.

Heterotopic ossification after central nervous system trauma: A current review

Neurogenic heterotopic ossification (NHO) is a disorder of aberrant bone formation affecting one in five patients sustaining a spinal cord injury or traumatic brain injury. Ectopic bone forms around joints in characteristic patterns, causing pain and limiting movement especially around the hip and elbow. Clinical sequelae of neurogenic heterotopic ossification include urinary tract infection, pressure injuries, pneumonia and poor hygiene, making early diagnosis and treatment clinically compelling. However, diagnosis remains difficult with more investigation needed. Our pathophysiological understanding stems from mechanisms of basic bone formation enhanced by evidence of systemic influences from circulating humor factors and perhaps neurological ones. This increasing understanding guides our implementation of current prophylaxis and treatment including the use of non-steroidal anti-inflammatory drugs, bisphosphonates, radiation therapy and surgery and, importantly, should direct future, more effective ones.

Combined pressure-thermal inactivation kinetics of Bacillus amyloliquefaciens spores in egg patty mince

Bacillus amyloliquefaciens is a potential surrogate for Clostridium botulinum in validation studies involving bacterial spore inactivation by pressure-assisted thermal processing. Spores of B. amyloliquefaciens Fad 82 were inoculated into egg patty mince (approximately 1.4 x 10(8) spores per g), and the product was treated with combinations of pressure (0.1 to 700 MPa) and heat (95 to 121 degrees C) in a custom-made high-pressure kinetic tester. The values for the inactivation kinetic parameter (D), temperature coefficient (zT), and pressure coefficient (zP) were determined with a linear model. Inactivation parameters from the nonlinear Weibull model also were estimated. An increase in process pressure decreased the D-value at 95, 105, and 110 degrees C; however, at 121 degrees C the contribution of pressure to spore lethality was less pronounced. The zP-value increased from 170 MPa at 95 degrees C to 332 MPa at 121 degrees C, suggesting that B. amyloliquefaciens spores became less sensitive to pressure changes at higher temperatures. Similarly, the zT-value increased from 8.2 degrees C at 0.1 MPa to 26.8 degrees C at 700 MPa, indicating that at elevated pressures, the spores were less sensitive to changes in temperature. The nonlinear Weibull model parameter b increased with increasing pressure or temperature and was inversely related to the D-value. Pressure-assisted thermal processing is a potential alternative to thermal processing for producing shelf-stable egg products.

DNA polymerase beta: structure-fidelity relationship from Pre-steady-state kinetic analyses of all possible correct and incorrect base pairs for wild type and R283A mutant

The kinetic parameters (kpol, Kd app) for all possible correct and incorrect pairing between the A, T, G, and C bases were determined for wild-type (WT) rat DNA polymerase beta (pol beta) and the R283A mutant under pre-steady-state kinetic assay conditions. The base substitution fidelities of these two proteins were then determined for all 12 possible mispairs representing the first complete fidelity analysis of polymerases using pre-steady-state kinetics. The results led to several significant findings: (i) For both WT and R283A, the fidelity is determined primarily by kpol (decreases for the incorporation of incorrect nucleotides) and to a small extent by Kd app (increases for the incorporation of incorrect nucleotides). (ii) In general, the fidelity for the Y.X (incorporation of dXTP opposite template dYMP) mismatch is different from that for the X.Y mismatch, reflecting the asymmetry of the active site. (iii) The fidelity of R283A is reduced in all 12 mispairs compared to that of WT. The extent of decrease varies from 200-fold for the A.G mispair to 2.5-fold for the T.C mispair. In general, the differences in fidelity between the mutant and WT are greater for purine.purine mismatches (up to 200-fold) than purine.pyrimidine, pyrimidine. purine, or pyrimidine.pyrimidine mismatches (up to 19-fold). (iv) Overall, the decreases in the fidelity of the R283A mutant are caused mainly by changes in the values of kpol; the kpol values of correct incorporations decrease to a greater extent for the R283A mutant with respect to WT than those of incorrect incorporations. With the exception of G.C, the values of Kd app for the WT and R283A mutant remain constant for correct pairings and vary by less than a factor of 4 for incorrect pairings. (v) For WT pol beta, the Kd app of G.C (8.6 microM) is distinctly smaller than that of other correct base pairs (41-108 microM). For the R283A mutant, the kpol of G.C is higher by a factor of 15-17.

Down-regulation of the stathmin/Op18 and FKBP25 genes following p53 induction

The p53 tumor suppressor protein can function as an activator and a repressor of gene transcription. Currently, the mechanism of transcriptional repression by p53 is poorly understood. To aid in clarifying this mechanism, we carried out studies designed to identify specific target genes that are down-regulated following p53 induction. Among the negative p53-response genes revealed by our screening protocols are those encoding stathmin (Op18), a tubulin-associated protein implicated in cell signaling pathways, and an FK506/rapamycin-binding protein, FKBP25. Stathmin and FKBP25 exhibit decreased expression in both human and murine immortalized and transformed cell lines following induction of wild-type p53 by several stimuli that result in DNA damage. Candidate p53-repressed genes such as these provide the necessary markers to delineate the mechanism and biological consequences of transcriptional repression mediated by p53.

The effect of lipid environment and retinoids on the ATPase activity of ABCR, the photoreceptor ABC transporter responsible for Stargardt macular dystrophy

ABCR is a photoreceptor-specific ATP-binding cassette transporter that has been linked to various retinal diseases, including Stargardt macular dystrophy, and implicated in retinal transport across rod outer segment (ROS) membranes. We have examined the ATPase and GTPase activity of detergent-solubilized and reconstituted ABCR. 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonic acid-solubilized ABCR had ATPase and GTPase activity (K(m) approximately 75 micrometer V(max) approximately 200 nmol/min/mg) that was stimulated 1.5-2-fold by all-trans-retinal and dependent on phospholipid and dithiothreitol. The K(m) for ATP decreased to approximately 25 micrometer after reconstitution, whereas the V(max) was strongly dependent on the lipid used for reconstitution. ABCR reconstituted in ROS phospholipid had a V(max) for basal and retinal activated ATPase activity that was 4-6 times higher than for ABCR in soybean or brain phospholipid. This enhanced activity was mainly due to the high phosphatidylethanolamine (PE) content of ROS membranes. PE was also required for retinoid-stimulated ATPase activity. ATPase activity of ABCR was stimulated by the addition of N-retinylidene-PE but not the reduced derivative, retinyl-PE. ABCR expressed in COS-1 cells also exhibited retinal-stimulated ATPase activity similar to that of the native protein. These results support the view that ABCR is an active retinoid transporter, the nucleotidase activity of which is strongly influenced by its lipid environment.