CREB binding protein (CBP) and p300 were both identified initially in protein interaction assays–the former through its association with the transcription factor CREB (Chrivia et al. 1993) and the latter through its interaction with the adenoviral-transforming protein E1A (Stein et al. 1990; Eckner et al. 1994). The recognition that these two proteins, one involved in transcription and the other in cell transformation, had highly conserved sequences suggested that they had the potential to participate in a variety of cellular functions (Fig. 1). Several excellent reviews (Janknecht and Hunter 1996; Shikama et al. 1997; Giles et al. 1998) have addressed the transcriptional coactivator functions of CBP/p300; this review focuses on the involvement of these proteins in the complex biological processes that affect cell growth, transformation, and development.

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CBP/p300 in cell growth, transformation, and development

Wnt growth factors regulate a variety of developmental processes by altering specific gene expression patterns. In vertebrates β-catenin acts as transcriptional activator, which is needed to overcome target gene repression by Groucho/TLE proteins, and to permit promoter activation as the final consequence of Wnt signaling. However, the molecular mechanisms of transcriptional activation by β-catenin are only poorly understood. Here we demonstrate that the closely related acetyltransferases p300 and CBP potentiate β-catenin-mediated activation of the siamois promoter, a known Wnt target. β-catenin and p300 also synergize to stimulate a synthetic reporter gene construct, whereas activation of the cyclin D1 promoter by β-catenin is refractory to p300 stimulation. Axis formation and activation of the β-catenin target genes siamois and Xnr-3 in Xenopus embryos are sensitive to the E1A oncoprotein, a known inhibitor of p300/CBP. The C-terminus of β-catenin interacts directly with a region overlapping the CH-3 domain of p300. p300 could participate in alleviating promoter repression imposed by chromatin structure and in recruiting the basal transcription machinery to promoters of particular Wnt target genes.

/pdf/the-p300-cbp-acetyltransferases-function-as-transcriptional-1pbyx9eml8.pdf

The p300/CBP acetyltransferases function as transcriptional coactivators of β‐catenin in vertebrates

A technique is described for specific, sensitive, quantitative, and rapid detection of biological targets by using superparamagnetic nanoparticles and a “microscope” based on a high-transition temperature dc superconducting quantum interference device (SQUID). In this technique, a mylar film to which the targets have been bound is placed on the microscope. The film, at room temperature and atmospheric pressure, is typically 40 μm from the SQUID, which is at 77 K in a vacuum. A suspension of magnetic nanoparticles carrying antibodies directed against the target is added to the mixture in the well, and 1-s pulses of magnetic field are applied parallel to the SQUID. In the presence of this aligning field the nanoparticles develop a net magnetization, which relaxes when the field is turned off. Unbound nanoparticles relax rapidly by Brownian rotation and contribute no measurable signal. Nanoparticles that are bound to the target on the film are immobilized and undergo Neel relaxation, producing a slowly decaying magnetic flux, which is detected by the SQUID. The ability to distinguish between bound and unbound labels allows one to run homogeneous assays, which do not require separation and removal of unbound magnetic particles. The technique has been demonstrated with a model system of liposomes carrying the FLAG epitope. The SQUID microscope requires no more than (5 ± 2) × 104 magnetic nanoparticles to register a reproducible signal.

https://www.pnas.org/content/pnas/97/26/14268.full.pdf

Ultrasensitive magnetic biosensor for homogeneous immunoassay

We are developing a biosensor system, the Bead ARray Counter (BARC), based on the capture and detection of micron-sized, paramagnetic beads on a chip containing an array of giant magnetoresistive (GMR) sensors. Here we describe the design and performance of our current chip with 64 sensor zones, compare its performance with the previous chip design, and discuss a simple analytical model of the sensor micromagnetics. With assay-ready Dynal M-280 microbeads (2.8 μm diameter), our threshold for detection is approximately 10 beads per 200 μm-diameter sensor. Single beads made of solid Ni 30 Fe 70 can easily be detected, but they must be made biocompatible. The relatively large size of our sensors helps to improve their practical sensitivity compared with other microsensor-based magnetic particle detectors.

https://www.nve.com/Downloads/Rife_Sensors_Actuators_A_revised_final.pdf

Design and Performance of GMR Sensors for the Detection of Magnetic Microbeads in Biosensors

We report a facile one-step hydrothermal approach to the synthesis of iron oxide (Fe3O4) nanoparticles (NPs) with controllable diameters, narrow size distribution, and tunable magnetic properties. In this approach, the iron oxide NPs were synthesized by oxidation of FeCl2·4H2O in basic aqueous solution under an elevated temperature and pressure. Transmission electron microscopy and X-ray diffraction studies reveal that the particles are highly crystalline and that the diameters of the particles can be tuned from 15 to 31 nm through the variation of the reaction conditions. The NPs exhibit high saturation magnetization in the range of 53.3−97.4 emu/g and their magnetic behavior can be either ferromagnetic or superparamagnetic depending on the particle size. A superconducting quantum interference device magnetorelaxometry study shows that the size of the NPs significantly affects the detection sensitivity. The investigated iron oxide NPs may find many potential biological applications in cancer diagnosis an...

/pdf/facile-hydrothermal-synthesis-of-iron-oxide-nanoparticles-1yx0pubjro.pdf

Facile hydrothermal synthesis of iron oxide nanoparticles with tunable magnetic properties

A system is developed to magnetically measure biological antigen-antibody reactions with a superconducting quantum interference device (SQUID) magnetometer. In this system, antibodies are labeled with magnetic nanoparticles of γ-Fe2O3, and the antigen-antibody reactions are measured by detecting the magnetic field from the magnetic nanoparticles. A setup of the system is described, and the sensitivity of the system is studied in terms of detectable weight of nanoparticles. Magnetic particles as small as 600 pg can be detected at present. An experiment is also conducted to measure antigen-antibody reaction with the present system. It is shown that the sensitivity of the present system is better than that of the conventional optical method. A one order of magnitude improvement of sensitivity will be realized by the sophistication of the present system.

https://iopscience.iop.org/article/10.1143/JJAP.38.L1102/pdf

Yuzuru Itoh

Papers

Detection of Magnetic Nanoparticles with Superconducting Quantum Interference Device (SQUID) Magnetometer and Application to Immunoassays

Molecular cloning and expression of Xenopus p300/CBP