Protein-DNA crosslinking

Schuessler FI, Schmerler-Dremel G, Danzer J.Jung-Korner E (1992) Ethanol radical-induced protein-DNA crosslinking. A radiolysis study. Int J Radiat Biol 62 517-526 Schuessler FI, Distel L, Sieber R (1997) Radiolysis of DNA in the presence of a protein studied by HPL-gel chromatography. Int J Radiat Biol 71 543-553... 

Schuster GB, Landman U (2004) The mechanism of long-distance radical cation transport in duplex DNA Ion-gated hopping of polaron-like distortions. Top Curr Chem 236 139-161 Schussler H, Jung E (1989) Protein-DNA crosslinks induced by primary and secondary radicals. Int J Radiat Biol 56 423-435... 

Fig. 7. Schematic representation of cisplatin bonding to DNA. (1) monofunctional binding (X = Cr, OH", OH2) (2) interstrand crosslinking (3) protein-DNA crosslinking (4) intrastrand crosslinking between adjacent guanines (5) intrastrand crosslinking between two guanines separated by a third base (6) intrastrand crosslinking at a-AG-unit...

The position of the general transcription factors with respect to promoter DNA in the initiation complex can be inferred from site-specific protein-DNA crosslinking (Ebright, 1998). The crosslinking data, taken... 

The list of the new gels for which phase transitions are possible is supplemented in the paper by Amiya and Tanaka, who discovered discrete collapse for the most important representatives of biopolymers - chemically crosslinked networks formed by proteins, DNA and polysaccharides [45]. Thus, it was demonstrated that discrete collapse is a general property of weakly charged gels and that the most important factor, which is responsible for the occurrence of this phenomenon, is the osmotic pressure of the system of counter ions. 

Rat liver and kidney nuclei (intraperitoneal exposure) DNA crosslinks, DNA-protein crosslinks, DNA strain breaks Cupo and Wetterhahn 1985 (III) Chromium oxide... 

UV radiation can result in the cross-finking of DNA to proteins (1). Crosslinks between different duplex DNA molecules (DNA-DNA crosslinks) have also been observed, mainly when DNA is irradiated in the dry state, in an extremely densely packed condition (such as in the heads of sahnon sperm), or in other special conformations (1). The spore photoproduct, formed in UV-irradiated dry DNA as described above, can arise not only between adjacent pyrimidines in the same chain but as a reaction between pyrimidines in different DNA chains (1). 

The Assessment of DNA Crosslinking by Alkaline Elution. DNA damage, that is, interstrand crosslinks, DNA-protein crosslinks, and strand breaks, was determined using the alkaline elution technique (7, ). Cells labeled with C-thymidine for 20-24 hr were deposited on a membrane filter and lysed with a detergent-containing solution. An alkaline solution (pH 12.1-12.2) was then slowly pumped through the filter, and fractions were collected to determine the rate of release of DNA from the filter. For assay of crosslinks, the cells were exposed to x-ray at 0 C prior to deposition on the filter. In order to improve quantitation, control cells labeled with H-thymidine and x-irradiated at 0 were mixed with the experimental Relabeled cells prior to deposition on the filters. The elution of H-DNA serves as an internal reference for normalization of the elution of C-DNA. 

Carboplatin and cyclophosphamide are indicated in the treatment of advanced ovarian carcinoma. Cisplatin and carboplatin produce predominantly interstrand DNA crosslinks rather than DNA-protein cross-links, and the effect is cell-cycle nonspecific. Carboplatin is not bound to plasma proteins, whereas platinum from carboplatin becomes bound to plasma protein and is eliminated slowly with a half-life of 5 days. The major route of elimination of carboplatin is the kidneys, and its doses should be reduced in renal impairment. Furthermore, the coadministration of aminoglycosides increases the chance of nephrotoxicity. Carboplatin causes anemia, neutropenia, leukopenia, and thrombocytopenia requiring transfusions. Cisplatin and, to a lesser extent, carboplatin cause emesis, which requires treatment with antiemetic agents. Alopecia, pain, and asthenia do occur (see also Figure 15). 

Crosslinking of DNA and proteins is a versatile method to study protein-DNA interactions. Among others, phosphoramidites of brominated or iodinated 2 -deoxycytidines [325], 2 -desoxuridines [326,327] and recently also of 2 -deoxyadenosines 132 have been used [328]. Nucleophilic replacement of the bromine by an amino group during deprotection does not occur when reaction conditions of concentrated ammonia solution for 24 h at room temperature are used after oligonucleotide synthesis. 

Figure 2.12 DNA crosslinking. The deleterious properties of nitrogen mustards are explained through the illustrated interstrand linkage mechanism that makes DNA impossible to duplicate or transcribe. Intrastrand crosslinking is the basis of action for anti-cancer drugs such as c/s-platin and carbo-platin. This is intended to prevent DNA duplication and hence cancer cell division. DNA crosslinking to proteins (such as histones) uses a non-covalent DNA intercalator with two azide functional groups. Both azides are activated for covalent coupling under photo-chemical conditions so that DNA subsequently becomes covalently linked to protein.

Radiolysis of DNA is modified in the presence of proteins. DNA-binding proteins induce DNA radioprotection toward double strand breaks (227, 228). Proteins such as bovine serum albumin (229, 230) lead to DNA-protein adducts under anaerobic as well as aerobic conditions. A similar result is obtained with chromatin (231). DNA double strand breaks also occur. However OH radicals do not crosslink DNA with lysozyme (232). Tyrosine and tryptophan residues are involved in the crosslinking process (233). 

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