Poly(ADP-ribose) polymerase 1 (PARP-1) regulates ribosomal biogenesis in Drosophila nucleoli

Poly(adp-ribose) polymerase 1 (parp1),a nuclear protein,utilizes nad to synthesize poly(ad-pribose) (padpr),resulting in both automodification and the modification of acceptor proteins. substantial amounts of parp1 and padpr (up to 50%) are localized to the nucleolus,a subnuclear organelle known as a region for ribosome biogenesis and maturation. at present,the functional significance of parp1 protein inside the nucleolus remains unclear. using parp1 mutants,we investigated the function of parp1,padpr,and parp1-interacting proteins in the maintenance of nucleolus structure and functions. our analysis shows that disruption of parp1 enzymatic activity caused nucleolar disintegration and aberrant localization of nucleolar-specific proteins. additionally,parp1 mutants have increased accumulation of rrna intermediates and a decrease in ribosome levels. together,our data suggests that parp1 enzymatic activity is required for targeting nucleolar proteins to the proximity of precursor rrna; hence,parp1 controls precursor rrna processing,post-transcriptional modification,and pre-ribosome assembly. based on these findings,we propose a model that explains how parp1 activity impacts nucleolar functions and,consequently,ribosomal biogenesis. © 2012 boamah et al.