Heat shock-induced interactions among nuclear HSFs detected by fluorescence cross-correlation spectroscopy

Mobility of Nucleostemin in Live Cells Is Specifically Related to Transcription Inhibition by Actinomycin D and GTP-Binding Motif

In vertebrates, nucleostemin (NS) is an important marker of proliferation in several types of stem and cancer cells, and it can also interact with the tumor-suppressing transcription factor p53. In the present study, the intra-nuclear diffusional dynamics of native NS tagged with GFP and two GFP-tagged NS mutants with deleted guanosine triphosphate (GTP)-binding domains were analyzed by fluorescence correlation spectroscopy. Free and slow binding diffusion coefficients were evaluated, either under normal culture conditions or under treatment with specific cellular proliferation inhibitors actinomycin D (ActD), 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), or trichostatin A (TSA). When treated with ActD, the fractional ratio of the slow diffusion was significantly decreased in the nucleoplasm. The decrease was proportional to ActD treatment duration. In contrast, DRB or TSA treatment did not affect NS diffusion. Interestingly, it was also found that the rate of diffusion of two NS mutants increased significantly even under normal conditions. These results suggest that the mobility of NS in the nucleoplasm is related to the initiation of DNA or RNA replication, and that the GTP-binding motif is also related to the large change of mobility.

Confocal Laser Scanning Microscopy and Fluorescence Correlation Methods for the Evaluation of Molecular Interactions

Confocal laser scanning microscopy (CLSM) and related microscopic techniques allow a unique and versatile approach to image and analyze living cells due to their specificity and high sensitivity. Among confocal related techniques, fluorescence correlation methods, such as fluorescence correlation spectroscopy (FCS) and dual-color fluorescence cross-correlation spectroscopy (FCCS), are highly sensitive biophysical methods for analyzing the complex dynamic events of molecular diffusion and interaction change in live cells as well as in solution by exploiting the characteristics of fluorescence signals. Analytical and quantitative information from FCS and FCCS coupled with fluorescence images obtained from CLSM can now be applied in convergence science such as drug delivery and nanomedicine, as well as in basic cell biology. In this chapter, a brief introduction into the physical parameters that can be obtained from FCS and FCCS is first provided. Secondly, experimental examples of the methods for evaluating the parameters is presented. Finally, two potential FCS and FCCS applications for convergence science are introduced in more detail.

Estrogen-related receptor gamma functions as a tumor suppressor in gastric cancer

The principle factors underlying gastric cancer (GC) development and outcomes are not well characterized resulting in a paucity of validated therapeutic targets. To identify potential molecular targets, we analyze gene expression data from GC patients and identify the nuclear receptor ESRRG as a candidate tumor suppressor. ESRRG expression is decreased in GC and is a predictor of a poor clinical outcome. Importantly, ESRRG suppresses GC cell growth and tumorigenesis. Gene expression profiling suggests that ESRRG antagonizes Wnt signaling via the suppression of TCF4/LEF1 binding to the CCND1 promoter. Indeed, ESRRG levels are found to be inversely correlated with Wnt signaling-associated genes in GC patients. Strikingly, the ESRRG agonist DY131 suppresses cancer growth and represses the expression of Wnt signaling genes. Our present findings thus demonstrate that ESRRG functions as a negative regulator of the Wnt signaling pathway in GC and is a potential therapeutic target for this cancer.

Fluorescence and Scattering Light Cross Correlation Spectroscopy and Its Applications in Homogeneous Immunoassay

In this work, we propose fluorescence and scattering light cross-correlation spectroscopy (FSCCS) based on laser confocal configuration using silver nanoparticle (SNPs) and Alexa Fluor 488 (Alexa) as probe pairs. FSCCS is a single molecule (particle) method, and its principle is similar to that of fluorescence cross-correlation spectroscopy (FCCS). We established the setup of FSCCS using single wavelength laser and developed an immunoassay model of FSCCS. The reliability and adaptability of FSCCS method were evaluated by homogeneous sandwich immunoassay mode. In the study, liver cancer biomarker alpha-fetoprotein (AFP) was used as an assay model, two different antibodies were labeled with SNPs and fluorophore Alexa Fluor 488, respectively. In the optimal conditions, the linear range of AFP covers 5 pM to 580 pM and the detection limit is 3.1 pM. This method was successfully applied for direct determination of AFP levels in human serum samples, and the obtained results were in good agreement with data obtained via ELISAs. The advantage of this method lies in its simplicity, attractive SNPs probes, high sensitivity and selectivity and high efficiency. We believe that FSCCS method exhibits promising potential applications in homogeneous bioassays and study on the molecular interaction and nanoparticle-molecule interaction.