Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 15220537

Analyzing cell cycle checkpoints after ionizing radiation.

Bo Xu·Michael B Kastan
View original source ↗Export metadata ↓

Abstract

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 measuring DNA synthesis in response to ionizing radiation, and the G2/M checkpoint assay by quantitating histone H3 phosphorylation after ionizing radiation.

Explore related subjects

BromodeoxyuridineCell CycleDNAFlow CytometryHeLa CellsHistonesHumansPhosphorylationRadiation, IonizingRadiation-Sensitizing AgentsJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Bo Xu, Michael B Kastan. 2004. Analyzing cell cycle checkpoints after ionizing radiation.. https://doi.org/10.1385/1-59259-811-0%3A283

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Cell cycle progression and de novo centriole assembly after centrosomal removal in untransformed human cells.

How centrosome removal or perturbations of centrosomal proteins leads to G1 arrest in untransformed mammalian cells has been a mystery. We use microsurgery and laser ablation to remove the centrosome from two types of normal human cells. First, we find that the cells assemble centrioles de novo after centrosome removal; thus, this phenomenon is not restricted to transformed cells. Second, normal cells can progress through G1 in its entirety without centrioles. Therefore, the centrosome is not a necessary, integral part of the mechanisms that drive the cell cycle through G1 into S phase. Third, we provide evidence that centrosome loss is, functionally, a stress that can act additively with other stresses to arrest cells in G1 in a p38-dependent fashion.

Bromodeoxyuridine↗
PubMed2007

Elevated sister chromatid exchange frequencies in dividing human peripheral blood lymphocytes exposed to 50 Hz magnetic fields.

The in vitro cytomolecular technique, sister chromatid exchange (SCE), was applied to test the clastogenic potentiality of extremely low frequency (ELF) electromagnetic fields (EMFs) on human peripheral blood lymphocytes (HPBLs). SCE frequencies were scored in dividing peripheral blood lymphocytes (PBLs) from six healthy male blood donors in two rounds of experiments, R1 and R2, to determine reproducibility. Lymphocyte cultures in the eight experiments conducted in each round were exposed to 50 Hz sinusoidal (continuous or pulsed) or square (continuous or pulsed) MFs at field strengths of 1 microT or 1 mT for 72 h. A significant increase in the number of SCEs/cell in the grouped experimental conditions compared to the controls was observed in both rounds. The highest SCE frequency in R1 was 10.03 for a square continuous field, and 10.39 for a square continuous field was the second highest frequency in R2. DNA crosslinking at the replication fork is proposed as a model which could explain the mechanistic link between ELF EMF exposure and increased SCE frequency.

Bromodeoxyuridine↗
PubMed2006

Loss of linker histone H1 in cellular senescence.

Cellular senescence is a tumor-suppressing mechanism that is accompanied by characteristic chromatin condensation called senescence-associated heterochromatic foci (SAHFs). We found that individual SAHFs originate from individual chromosomes. SAHFs do not show alterations of posttranslational modifications of core histones that mark condensed chromatin in mitotic chromosomes, apoptotic chromatin, or transcriptionally inactive heterochromatin. Remarkably, SAHF-positive senescent cells lose linker histone H1 and exhibit increased levels of chromatin-bound high mobility group A2 (HMGA2). The expression of N-terminally enhanced green fluorescent protein (EGFP)-tagged histone H1 induces premature senescence phenotypes, including increased levels of phosphorylated p53, p21, and hypophosphorylated Rb, and a decrease in the chromatin-bound endogenous histone H1 level but not in p16 level accumulation or SAHF formation. However, the simultaneous ectopic expression of hemagglutinin-tagged HMGA2 and N-terminally EGFP-tagged histone H1 leads to significant SAHF formation (P < 0.001). It is known that histone H1 and HMG proteins compete for a common binding site, the linker DNA. These results suggest that SAHFs are a novel type of chromatin condensation involving alterations in linker DNA-binding proteins.

Bromodeoxyuridine↗