Allosteric Tuning of Caspase-7: Establishing the Nexus of Structure and Catalytic Power

Caspase-7 (C7), a cysteine protease involved in apoptosis, is a valuable drug target for its role in human diseases (e.g. Parkinson's, Alzheimer's, sepsis). The C7 allosteric site has great potential for small molecule targeting, but numerous drug discovery efforts have identified precious few allosteric inhibitors. Here we present the first selective, drug-like inhibitor of C7 along with several other improved inhibitors based on our previous fragment hit. We also provide a rational basis for the impact of allosteric binding on the C7 catalytic cycle using an integrated approach including X-ray crystallography, stopped-flow kinetics, and molecular dynamics simulations. Our findings suggest allosteric binding disrupts C7 pre-acylation via neutralization of the catalytic dyad, displacement of substrate from the oxyanion hole, and altered dynamics of substrate binding loops. This work advances drug targeting efforts and bolsters our understanding of allosteric structure activity relationships (ASARs).

Redox regulation of RAD51 Cys319 and homologous recombination by peroxiredoxin 1

RAD51 is a critical recombinase that functions in concert with auxiliary mediator proteins to direct the homologous recombination (HR) DNA repair pathway. We show that Cys319 RAD51 possesses nucleophilic characteristics and is important for irradiation-induced RAD51 foci formation and resistance to inhibitors of poly (ADP-ribose) polymerase (PARP). We have previously identified that cysteine (Cys) oxidation of proteins can be important for activity and modulated via binding to peroxiredoxin 1 (PRDX1). PRDX1 reduces peroxides and coordinates the signaling actions of protein binding partners. Loss of PRDX1 inhibits irradiation-induced RAD51 foci formation and represses HR DNA repair. PRDX1-deficient human breast cancer cells and mouse embryonic fibroblasts display disrupted RAD51 foci formation and decreased HR, resulting in increased DNA damage and sensitization of cells to irradiation. Following irradiation cells deficient in PRDX1 had increased incorporation of the sulfenylation probe DAz-2 in RAD51 Cys319, a functionally-significant, thiol that PRDX1 is critical for maintaining in a reduced state. Molecular dynamics (MD) simulations of dT-DNA bound to a non-oxidized RAD51 protein showed tight binding throughout the simulation, while dT-DNA dissociated from an oxidized Cys319 RAD51 filament. These novel data establish RAD51 Cys319 as a functionally-significant site for the redox regulation of HR and cellular responses to IR.

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A functionally-significant Cys319 was identified in RAD51 that possesses nucleophilic characteristics.

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RAD51 Cys319 plays a central role in RAD51-mediated repair of DNA double strand breaks (DSB).

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Loss of peroxiredoxin 1 (PRDX1) impairs DNA DSB repair by homologous recombination and results in DNA damage.

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PRDX1 is critical for maintaining RAD51 Cys319 in a reduced state.

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Molecular dynamic (MD) simulations suggest ssDNA to dissociate from sulfenylated and not reduced RAD51 Cys319.

Screening for second cancers and osteoporosis in long-term survivors

PURPOSE

The purpose of this preliminary study was to describe the extent to which healthcare providers recommend the screening strategies for early detection described by the American Cancer Society (ACS), for breast, gynecologic, and colorectal cancer, and by the National Osteoporosis Foundation (NOF), for osteoporosis, to women who are long-term survivors of breast, ovarian, or endometrial cancer.

DESCRIPTION OF THE STUDY

A four-part survey was developed for this study, with the first three parts based on the ACS guidelines for breast, gynecologic, and colorectal cancer screening and the NOF guidelines for osteoporosis screening. The fourth part related to personal characteristics, setting, knowledge, and perceptions of the nurses surveyed. A random sample of outpatient nurses was obtained from the Oncology Nursing Society. Of 668 nurses, 321 (48%) responded (Oncology Certified Nurse (OCN) 68.1%; Advanced Oncology Certified Nurse (AOCN) 16.6%).

RESULTS

The most consistently performed screenings that were reported were mammogram (range 74.2-87.7%), professional breast examination (range 73.9-83.7%), and Pap test and pelvic examination (range 61.8-85.2%). The least frequently performed screenings are flexible sigmoidoscopy/colonoscopy (range 20.2-27.7%), bone mineral density testing (range 16.9-19.0%), and height measurement (range 22.5-28.3%). Less than one third of survivors are offered counseling on strategies to promote bone health.

CLINICAL IMPLICATIONS

Knowledge of factors associated with osteoporosis and the use of screening strategies for second malignancies in survivors of breast, ovarian, and endometrial cancers can be used to implement activities such as patient education and clinical practice protocols that will increase the use of current screening recommendations.

Presentation of nursing diagnosis content in fundamentals of nursing textbooks

The technique and rationale for the use of nursing diagnosis generally are introduced early in the undergraduate curriculum. The three purposes of this descriptive study were to describe the general characteristics and presentation of content on nursing diagnosis in fundamentals of nursing textbooks; describe how the content from the theoretical chapter(s) in nursing diagnosis is carried through in the clinical chapters; and describe how content on diagnostic errors is presented. Although most of the textbooks presented content on nursing diagnosis in a similar fashion, the clinical chapters of the books did not follow the same pattern. Content on diagnostic errors was inconsistent. Educators may find this an effective methodology for reviewing textbooks.