Azadeh Mohammadgholi; Azra rabani chadegani
Abstract
Vincristine is the most effective anticancer drug, widely used in the treatment of various cancers. Chromatin is composed of nucleosome units consisted of DNA and histone proteins. In the present study, for the first time the interaction of anticancer drug vincristine with histone H1 and core histone ...
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Vincristine is the most effective anticancer drug, widely used in the treatment of various cancers. Chromatin is composed of nucleosome units consisted of DNA and histone proteins. In the present study, for the first time the interaction of anticancer drug vincristine with histone H1 and core histone proteins in solution was investigated using fluorescence, UV and CD spectroscopy techniques. The results showed that in the presence of vincristine, fluorescence emission intensities were reduced in a dose dependent manner, representing quenching of the drug with aromatic residues located in the globular head domain of histone proteins. Stern-Volmer constant and binding affinity of the drug to histone H1 was higher than core histone proteins. The binding of vincristine to histones induced structural changes in circular dichroism spectra revealing increase of α-helix content of the histones. Moreover, vincristine increased UV absorbance of H1 and core histones at 210 nm (hyperchromicity). In conclusion it is suggested that vincristine, by its domains, can penetrate into globular head domain of histones. Also the binding affinity of vincristine to histone H1 is higher than to core histones, possibly because H1 is located in linker region which is more exposed and accessible to environment
Ozra Rabbani Chadgani; Massoumeh Babai; Parstou Shahmir
Abstract
In the present study the effect of daunomycin and vinorelbine on chromatin proteins in alveolar macrophages was investigated and compared. Alveolar macrophages were prepared by lavage and incubated in the absence and presence of various concentrations of the drugs. The histone and non-histone proteins ...
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In the present study the effect of daunomycin and vinorelbine on chromatin proteins in alveolar macrophages was investigated and compared. Alveolar macrophages were prepared by lavage and incubated in the absence and presence of various concentrations of the drugs. The histone and non-histone proteins were then extracted and analyzed. The results showed that upon increasing drugs concentration viability of the cells was decreased thus at 80 g/ml, 73% and 50% viability was obtained for daunomycin and vinorelbine respectively. Low concentrations of the drugs had no considerable effect on chromatin proteins content but at higher concentrations the amount of histone H1 was significantly decreased, whereas the content of core histones remained unchanged. The content of H1 subtype, H1o and HMG proteins were also decreased as drugs concentrations increased. Western blot analysis against histone and HMG proteins antisera also confirmed the results. Moreover, staining of the cells with ethidium bromide/acridine orange revealed higher toxicity of vinorelbine compared to daunomycin. From the results it is concluded that vinorelbine exhibits higher affinity to chromatin of alveolar macrophages than daunomycin. Binding of the drugs induce chromatin compaction possibly through histone-histone or histone-DNA cross links thus the proteins were not extractable with manual procedures.
zahra Hajihassan; Azra Rabbani-Chadegani
Abstract
Actinomycin D and mitoxantrone are anticancer drugs widely used in the treatment of a variety of cancers. DNA has been introduced as a main target for these drugs which results in inhibition of both DNA replication and RNA transcription. In the cell nucleus, DNA is not naked but is complexed with histone ...
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Actinomycin D and mitoxantrone are anticancer drugs widely used in the treatment of a variety of cancers. DNA has been introduced as a main target for these drugs which results in inhibition of both DNA replication and RNA transcription. In the cell nucleus, DNA is not naked but is complexed with histone proteins producing a compact structure called chromatin. In the present study we have investigated and compared the binding affinity of these drugs to rat liver chromatin. The results of gel electrophoresis and UV-Vis spectroscopy showed that both drugs bound to chromatin but mitoxantrone exhibited higher affinity compared to actinomycin D. Disappearance of histones on the gel and reduction of the absorbencies at 608 and 440 nm, corresponding mitoxantrone and actinomycin D respectively, suggest compaction/aggregation of the chromatin. The binding isotherms demonstrated a positive cooperative binding pattern for both drugs with binding constants (ka) of 7.1×106 M-1 and 0.35×105 M-1 for mitoxantrone and actinomycin D respectively suggesting higher binding affinity of mitoxantrone to chromatin compared to actinomycin D. In addition Gibbs free energy for the binding of both drugs was negative demonstrating that the reaction is spontaneously. It is concluded that actinomycin D preferentially interacts with DNA molecule, whereas, mitoxantrone binds to nucleoprotein structure of chromatin implying the role of histone proteins in this binding process.
