细胞技术

Base excision repair is a major mechanism for correcting modified bases. The first step of this repair mechanism is the removal of a modified base by a specific DNA-N-glycosylase to leave an apurinic/apyrimidinic (AP) site. Subsequently, the AP site is repaired through sequential reactions, ...

Apurinic/apyrimidinic (AP) sites are one of the more common lesions formed in DNA that, if left unrepaired, can represent potential sites of mutation (1). To illustrate the importance of these sites, all organisms that have thus far been tested have been found to contain enzymes that incise abasic ...

Several types of DNA lesions are formed on irradiation of cells with ultraviolet (UV) light (1,2). The two most frequent lesions are the cyclobutane pyrimidine dimers (CPDs) and the pyrimidine (6-4) pyrimidone photoproducts ( photoproducts; PPs). In addition, UV irradiation produces, alt ...

Physical and chemical agents in the environment, those used in clinical applications, or encountered during recreational exposures to sunlight, induce damages in DNA. Understanding the biological impact of these agents requires quantitation of the levels of such damages in labora ...

Ultraviolet (UV) radiation that overlaps the absorption spectrum of DNA induces a variety of photoproducts. Because stratospheric ozone screens out shorter UV wavelengths, DNA-damaging solar irradiance at the terrestrial surface is confined to the UV-B band (290–320 nm). However, g ...

Radioimmunoassay (RIA) is a competitive binding assay between an unlabeled and a radiolabeled antigen for binding to antibody raised against that antigen. For the development of this technique, Yalow and Berson (1) received the Nobel Prize in Medicine. For detailed theory and troublesh ...

Measurement of DNA damage can be difficult if the levels of damage are small. For example, the ultraviolet (UV) radiation in sunlight creates cyclobutane pyrimidine dimers (CPDs), but this type of damage is rapidly repaired. The steady-state level of CPDs is thus low, and sensitive methods are req ...

The dot-blot method described here can be used to measure repair of pyrimidine-pyrimidone 6-4 photoproducts (PPs) and cyclobutane pyrimidine dimers (CPDs) in total genomic DNA from any organism. The DNA does not have to be especially intact nor is it necessary to have any sequence information. ...

The adverse biological consequences of unrepaired toxic UV-B-induced photoproducts in DNA, mostly cyclobutane pyrimidine dimers (CPDs) and pyrimidine-(6-4′)-pyrimidone photoproducts , are touched on in Chapters 4, 15, and 18. Enzymes that use UV-A/blue-light energy to reverse CPDs ...

DNA mismatch repair plays an important role in mutation avoidance by recognizing and correcting mismatched bases and loops prior to their fixation as mutations. When mismatch repair is defective, cells exhibit elevated rates of spontaneous mutations. For example, microsatellite s ...

During the last 20 years, the cloning and identification of DNA repair genes in bacteria, yeast, human, mouse, and other organisms have been an expanding enterprise. Gene/cDNA isolation and analysis is a critical step toward discovering gene/protein function by enabling subsequent char ...

Cell lines with an increased sensitivity to mutagens, such as ultraviolet (UV) light, X-rays, alkylating compounds, and crosslinking agents, are defective in a cellular response to these agents. These responses include mechanisms that process DNA lesions, scavenge free radicals, or re ...

This chapter describes a method to isolate γ-ray hypersensitive mutants of Arabidopsis thaliana from ethyl methanesulfonate- (EMS) treated seed (1). The mutants are identified by visible symptoms of extreme radiation damage 10–15 d following exposure of seedlings to a threshold 10-k ...

UV radiation induces two major DNA damage products: the cyclobutane pyrimidine dimer (CPD) and the pyrimidinepyrimidinone dimer (or photoproduct; PP). The biological effects of both lesions have been studied in microbial and mammalian systems. Pyrimidine dimers have been shown to act ...

The fruitfly Drosophila melanogaster offers numerous advantages as a metazoan model for genetic dissection of conserved biological processes, such as DNA repair. Its ease of culture, short generation time, small number of linkage groups (2n=8), and giant polytene chromosomes, combi ...

The nematode Caenorhabditis elegans has gained widespread popularity for use in addressing many biological problems, particularly those relating to development (for brief topical reviews, see 1–5; for comprehensive treatises, see 6–10). This can be attributed to both inherent pro ...

Eukaryotic cells have the ability to influence progression through the cell cycle in response to internal and external inputs of “information”. They do so by using feedback control mechanisms able to arrest mitosis in response to different cellular events. Such active mechanisms capab ...

Considerations in rational designs of CPP-based transcutaneous delivery systems are described. Impact of design considerations of nonclinical and clinical results are presented in detail.

Since the discovery over 15 years ago of a protein transcription factor that possessed the ability to cross the plasma membrane, cell-penetrating peptides (CPPs) have been evaluated for the ability to transport diverse cargoes into cells, tissues, and organs. Certain CPPs have been used for t ...

To enhance the cytosolic delivery of therapeutic drugs and genes, pH-sensitive and membrane fusiogenic peptides have been employed as additives for facilitating their endosomal escape. GALA is such a peptide composed of repeating sequences of Glu-Ala-Leu-Ala, which are designed to m ...