Histones are classically known to organize the eukaryotic DNA into chromatin. They are one of the key players in regulating transcriptionally permissive and non-permissive states of the chromatin. Nevertheless, their context-dependent appearance within the cytoplasm and systemic circulation has also been observed. The past decade has also witnessed few scientific communications on the existence of vesicle-associated histones. Diverse groups have attempted to determine the significance of these extra-nuclear histones so far, with many of those studies still underway. Of note amongst these are interactions of extra-nuclear or free histones with cellular membranes, mediated by mutual cationic and anionic natures, respectively. It is here aimed to consolidate the mechanism of formation of extra-nuclear histones; implications of histone-induced membrane destabilization and explore the mechanisms of their association/release with extracellular vesicles, along with the functional aspects of these extra-nuclear histones in cell and systemic physiology.
Glutamate dehydrogenase (GDH) enzyme is recently being reported to be present in the nucleus in addition to the mitochondria in a number of organisms. Here we investigated the distribution of GDH in liver and brain tissues of chicken. Polyclonal anti-GDH antibody against bovine GDH was raised by us, which was later shown to be immunereactive to chicken GDH. The nuclear and the mitochondrial extracts from liver and brain tissues of chicken were made as described. By quantitative immunoreactivity, it was revealed that the nuclear GDH expressed in comparable efficiencies in the liver and brain. However, the activity of the brain nuclear GDH was lower than the liver counterparts. The allosteric regulation pattern for the brain nuclear GDH was also different from the other corresponding fractions and it was speculated that the brain nuclear GDH was inactive. The liver and brain nuclear GDH were purified to homogeneity and comparison of specific activities of both the GDH ruled out the existence of any inhibitor in the brain nuclear GDH. It is hypothesized that the inactivation of the brain nuclear GDH in chicken could be due to some already known posttranslational modification. The present report throws light on the differential regulation pattern of GDH enzyme.
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