Cytoplasmic poly(ADP-ribose) polymerase associated with free messenger ribonucleoprotein particles in rat brain

Proteome-wide identification of poly(ADP-ribose) binding proteins and poly(ADP-ribose)-associated protein complexes

Poly(ADP-ribose) (pADPr) is a polymer assembled from the enzymatic polymerization of the ADP-ribosyl moiety of NAD by poly(ADP-ribose) polymerases (PARPs). The dynamic turnover of pADPr within the cell is essential for a number of cellular processes including progression through the cell cycle, DNA repair and the maintenance of genomic integrity, and apoptosis. In spite of the considerable advances in the knowledge of the physiological conditions modulated by poly(ADP-ribosyl)ation reactions, and notwithstanding the fact that pADPr can play a role of mediator in a wide spectrum of biological processes, few pADPr binding proteins have been identified so far. In this study, refined in silico prediction of pADPr binding proteins and large-scale mass spectrometry-based proteome analysis of pADPr binding proteins were used to establish a comprehensive repertoire of pADPr-associated proteins. Visualization and modeling of these pADPr-associated proteins in networks not only reflect the widespread involvement of poly(ADP-ribosyl)ation in several pathways but also identify protein targets that could shed new light on the regulatory functions of pADPr in normal physiological conditions as well as after exposure to genotoxic stimuli.

Poly(ADP-ribose) polymerase is found in both the nucleus and cytoplasm of human CNS neurons

There is evidence that inhibitors of poly(ADP-ribose) polymerase (PARP) may be therapeutically useful in neurodegenerative diseases. Using immunocytochemistry, we have investigated the distribution of PARP in the human CNS. Some neuronal groups showed cytoplasmic staining in addition to the expected staining of nuclei. Considerable variation between different neuronal groups was noted: motor neurons in the spinal cord showed greatest cytoplasmic staining, whereas staining was virtually absent in other neurons, notably in the hippocampus. These results indicate that PARP can be associated with sub-cellular components other than the nucleus, and may indicate additional roles for this enzyme.

ADP-ribosylation of proteins in brain regions of rats during postnatal development

Post-translational modifications of chromatin-bound proteins play an important role in the regulation of eukaryotic gene expression. Processes such as acetylation, methylation, phosphorylation and ADP-ribosylation may alter the interaction of these proteins with DNA and consequently affect chromatin conformation and the binding of enzymes and other molecules involved in the regulation of gene expression. In the present study the process of ADP-ribosylation of chromosomal proteins (histone and non-histone proteins) in some rat brain regions during postnatal development was investigated; also the effect of epidermal growth factor (EGF) on this process in fetal brain slices was studied. It has been found that the process of ADP-ribosylation of total histones extracted from rat cerebral cortex and cerebellum at 1, 10 and 30 days of age, increases from 1 to 10 days of age (i.e. the period of maximal cell proliferation) and decreases thereafter, while the process of ADP-ribosylation of non-histone proteins (NHPs) sharply decreases during the same developmental period. The addition of EGF to fetal brain slices causes a significant increase of ADP-ribosylation of total histones (particularly of the histone H1 fraction) and also of NHPs and microsomal proteins. This result is in agreement with the effect of EGF as a mitogen factor, previously shown in astroglial cell cultures.