Assembly of Slx4 signaling complexes behind DNA replication forks

Obstructions to replication fork progression, referred to collectively as DNA replication stress, challenge genome stability. In Saccharomyces cerevisiae, cells lacking RTT107 or SLX4 show genome instability and sensitivity to DNA replication stress and are defective in the completion of DNA replication during recovery from replication stress. We demonstrate that Slx4 is recruited to chromatin behind stressed replication forks, in a region that is spatially distinct from that occupied by the replication machinery. Slx4 complex formation is nucleated by Mec1 phosphorylation of histone H2A, which is recognized by the constitutive Slx4 binding partner Rtt107. Slx4 is essential for recruiting the Mec1 activator Dpb11 behind stressed replication forks, and Slx4 complexes are important for full activity of Mec1. We propose that Slx4 complexes promote robust checkpoint signaling by Mec1 by stably recruiting Dpb11 within a discrete domain behind the replication fork, during DNA replication stress.     

p53 Protein-mediated Regulation of Phosphoglycerate Dehydrogenase (PHGDH) Is Crucial for the Apoptotic Response upon Serine Starvation

Although p53 is frequently mutated in human cancers, about 80% of human melanomas retain wild-type p53. Here we report that PHGDH, the key metabolic enzyme that catalyzes the rate-limiting step of the serine biosynthesis pathway, is a target of p53 in human melanoma cells. p53 suppresses PHGDH expression and inhibits de novo serine biosynthesis. Notably, upon serine starvation, p53-mediated cell death is enhanced dramatically in response to Nutlin-3 treatment. Moreover, PHGDH has been found recently to be amplified frequently in human melanomas. We found that PHGDH overexpression significantly suppresses the apoptotic response, whereas RNAi-mediated knockdown of endogenous PHGDH promotes apoptosis under the same treatment. These results demonstrate an important role of p53 in regulating the serine biosynthesis pathway through suppressing PHGDH expression and reveal serine deprivation as a novel approach to sensitize p53-mediated apoptotic responses in human melanoma cells.     

Highly selective recognition of naphthol isomers based on the fluorescence dye-incorporated SH-β-cyclodextrin functionalized gold nanoparticles

In present work, a rhodamine 6G (Rh 6G)-incorporated β-cyclodextrin functionalized gold nanoparticle (Rh 6G-CD-AuNP) based fluorescent assay has been successfully developed for recognizing/detecting the structural isomers, α-naphthol and β-naphthol, in aqueous solution. The β-cyclodextrin functionalized gold nanoparticles (CD-AuNPs) are achieved by conjugating the thiolated β-cyclodextrin (SH-β-CD) with AuNPs via S-Au covalent bonds. Rhodamine 6G (Rh 6G) is chosen as a fluorescent probe in this approach because it can be strongly absorbed on the surface of AuNP by noncovalent interaction. After binding with β-CD cavity, the naphthols enable to act as electron transfer quenchers of Rh 6G, which lead to significant fluorescence quenching of the dye. Because of different association ability of naphthol isomers with the β-CD cavity, the assay can selectively distinguish α-naphthol and β-naphthol with reasonable sensitivity. Detection of naphthols down to 8 nM with a dynamic range of nearly three orders of magnitude (0.01-8 μM) for α-naphthol and 50 nM with two orders of magnitude (0.1-20 μM) for β-naphthol is demonstrated, respectively. The ability of the method for detecting the content of α-naphthol or β-naphthol in the different naphthol mixtures has also been evaluated.     

The Arf GAP CNT-2 regulates the apoptotic fate in C. elegans asymmetric neuroblast divisions

During development, all cells make the decision to live or die. Although the molecular mechanisms that execute the apoptotic program are well defined, less is known about how cells decide whether to live or die. In C.?elegans, this decision is linked to how cells divide asymmetrically [1, 2]. Several classes of molecules are known to regulate asymmetric cell divisions in metazoans, yet these molecules do not appear to control C.?elegans divisions that produce apoptotic cells [3]. We identified CNT-2, an Arf GTPase-activating protein (GAP) of the AGAP family, as a novel regulator of this type of neuroblast division. Loss of CNT-2 alters daughter cell size and causes the apoptotic cell to adopt the fate of its sister cell, resulting in extra neurons. CNT-2's Arf GAP activity is essential for its function in these divisions. The N terminus of CNT-2, which contains?a GTPase-like domain that defines the AGAP class of Arf GAPs, negatively regulates CNT-2's function. We provide evidence that CNT-2 regulates receptor-mediated endocytosis and consider the implications of its role in asymmetric cell divisions.     

Pharmacophore-based discovery of triaryl-substituted imidazole as new telomeric G-quadruplex ligand

Discovery of potent and selective ligands for telomeric G-quadruplex DNA is a challenging work. Through a combination approach of pharmacophore model construction, model validation, database virtual screening, chemical synthesis and interaction evaluation, we discovered and confirmed triaryl-substituted imidazole TSIZ01 to be a new telomeric G-quadruplex ligand with potent binding and stabilizing activity to G-quadruplex DNA, as well as a 8.7-fold selectivity towards telomeric G-quadruplex DNA over duplex DNA.     

RNA干扰在疾病治疗上的应用

RNA干扰(RNA interference,RNAi)是一种双链RNA分子在mRNA水平上引发的特异性基因沉默现象。RNAi在基因治疗方面表现出了光明的前景,已成功地应用于多种疾病的临床治疗。本文主要介绍了RNAi在疾病治疗上的应用及研究进展。     

Design, synthesis, and biological evaluation of curcumin analogues as multifunctional agents for the treatment of Alzheimer's disease

A series of novel curcumin analogues were designed, synthesized, and evaluated as potential multifunctional agents for the treatment of AD. The in vitro studies showed that these compounds had better inhibitory properties against Aβ aggregation than curcumin. Superior anti-oxidant properties (better than the reference compound Trolox) of these compounds were observed by the oxygen radical absorbance capacity (ORAC) method and a cell-based assay using DCFH-DA as a probe. In addition they were able to chelate metals such as iron and copper and decrease metal-induced Aβ aggregation. The structure-activity relationships were discussed. The results suggested that our curcumin analogues could be selected as multifunctional agents for further investigation of AD treatment.