前沿科技及其它

To determine the activity of all human Cdc25 phosphatases, two different methods are described. For assaying phosphatase activities of recombinant Cdc25 proteins produced in Escherichia coli or insect cells, a fluorimetric assay using fluorescein diphosphate (FDP) as a substrate ...

To maintain genomic integrity against various kinds of genotoxic stress, cells have multiple checkpoints in the cell cycle. When one of the cell cycle events, such as DNA synthesis, DNA repair, and chromosomal segregation, has not been successfully completed, checkpoints will delay prog ...

Small interfering RNA (siRNA) technology has emerged as a powerful genetic tool to investigate gene function in mammalian cells. Here we use siRNA to study a mediator of DNA damage-checkpoint protein 1 (MDC1), previously known as Kiaa0170 or NFBD1, in DNA damage responses. We show that MDC1 siRNA s ...

We describe here the cloning of full-length ataxia-telangiectasia mutated (ATM) cDNA and characterization of its activity. Full-length ATM cDNA is cloned into an inducible EBV-based vector (pMEP4) and its expression analyzed in a stably transfected cell line. ATM protein induction is m ...

The mitotic checkpoint prevents cells with unaligned chromosomes from prematurely exiting mitosis by inhibiting the anaphase-promoting complex/cyclosome (APC/C) from targeting key proteins for ubiquitin-mediated proteolysis. Great efforts have been made recently to i ...

The spindle-assembly checkpoint involves signaling at kinetochores, which leads to the arrest of mitotic progression in the absence of microtubule attachment or spindle tension. Here, we detail procedures for the analysis of the spindle-assembly checkpoint in adherent mammali ...

The spindle checkpoint helps to ensure the fidelity of chromosome segregation during mitosis and meiosis. In response to sister chromatids not properly attached to the mitotic spindle, this checkpoint blocks the activity of a large ubiquitin protein ligase complex, called the anapha ...

Cell cycle checkpoints play a key role in maintaining genome stability by monitoring the order and integrity of cell division events. Checkpoints induced by DNA damage function to limit the propagation of potentially deleterious mutations. The retinoblastoma tumor suppressor (RB) ...

The completion of the human genome sequence and availability of cDNA microarray technology provide new approaches to explore global cellular regulatory mechanisms. Here we present a strategy to identify genes regulated by specific transcription factors in the human genome, and app ...

The functions of the retinoblastoma protein (pRb) are in part regulated by reversible and cell cycle-dependent phosphorylation. While the regulation of pRb by cyclin-dependent kinases (Cdks) has been studied extensively, the role(s) of protein phosphatase 1 (PP1) in controlling pRb a ...

p21WAF1 was originally identified as a protein that binds and inhibits cyclin-dependent kinases (CDKs). p21WAF1 is recognized to have at least two separate roles—first as a CDK inhibitor, and second as an inhibitor of PCNA, an accessory protein of DNA polymerase δ. p21WAF1 plays a critical role in ...

The cyclin-dependent kinase (CDK) inhibitor p21CDKN1A (also known as p21waf1/cip1) is a well known player of the G1 and G2 phase cell cycle checkpoints, which are activated in response to DNA damage. In addition, p21 interacts directly with proliferating cell nuclear antigen (PCNA), thereby ...

In recent years, gene expression quantitation of tumor cells has become of principal importance to analyze gene patterns responsible for cancer development, progression, and resistance to treatment. Whereas semi-quantitative methods, such as Northern blotting analysis, all ...

The activity of cyclin-dependent kinases (CDKs) lies at the heart of cell cycle and checkpoint control. These complexes have been called the “cell cycle engine,” as it is their enzymatic activity that pushes the cells through the cell-division cycle. If this activity is down-regulated, for exa ...

Members of the phosphoinositide-3-kinase-related kinase (PIKK) family, which includes mTOR, ATM, ATR, and hSMG-1, play important roles in regulating the cellular response to environmental stimuli. Despite the similarity of their catalytic domain to that of phosphoinositide-3- ...

Mammalian CHK1 is a Ser/Thr effector kinase that plays critical roles in the DNA damage-activated cell cycle checkpoint signaling pathway downstream of ATR (ATM and Rad3-related protein kinase). This chapter is focused on describing an assay to measure CHK1 activity in vitro. The basic mech ...

Cell cycle checkpoints respond to a wide range of stresses to prevent compromise to the integrity of the cell. The best studied checkpoints are those induced by genotoxic agents that cause DNA damage. Histone deacetylase inhibitors not only increase the acetylation state of chromatin hist ...

It is frequently necessary to examine the biochemical effects of ectopically expressed proteins or short hairpin (sh) RNA-mediated protein knock-down in intact cells. Plasmids that direct the expression of ectopic proteins or shRNAs can be conveniently introduced into cells by tran ...

The G2 checkpoint blocks cells from entering mitosis when DNA is damaged, and helps to protect the integrity of the genome. Tumor cells contain mutations that can inactivate checkpoints, and the inactivation of the G2 checkpoint can induce genomic instability and alter cellular responses ...

Several methods to measure cell cycle perturbation after exposure to ionizing radiation are presented in this chapter. These methods include the G1 checkpoint assay by 5′ bromode-oxyuridine (BrdUrd) labeling followed by flow cytometric analysis, the S-phase checkpoint assay by mea ...