PARP-1 and PARP-2 interact with nucleophosmin/B23 and accumulate in transcriptionally active nucleoli

Abstract

The DNA damage-dependent poly(ADP-ribose) polymerases-1 and -2 (PARP-1 and PARP-2) are survival factors that share overlapping functions in the detection, signaling and repair of DNA strand breaks resulting from genotoxic lesions in mammalian cells. Here we show that PARP-1 and PARP-2 subnuclear distributions partially overlap, with both proteins accumulating within the nucleolus independently of each other. PARP-2 is enriched within the whole nucleolus and partially colocalizes with the nucleolar factor nucleophosmin/B23. We have identified a nuclear localization signal and a nucleolar localization signal within the N-terminal domain of PARP-2. PARP-2, like PARP-1, interacts with B23 through its N-terminal DNA binding domain. This association is constitutive and does not depend on either PARP activity or ribosomal transcription, but is prevented by mutation of the nucleolar localization signal of PARP-2. PARP-1 and PARP-2, together with B23, are delocalized from the nucleolus upon RNA polymerase I inhibition whereas the nucleolar accumulation of all three proteins is only moderately affected upon oxidative or alkylated DNA damage. Finally, we show that murine fibroblasts deficient in PARP-1 or PARP-2 are not affected in the transcription of ribosomal RNAs. Taken together, these results suggest that the biological role of PARP-1 and PARP-2 within the nucleolus relies on functional nucleolar transcription, without any obvious implication of either PARP on this major nucleolar process.

Differential Effect of PARP-2 Deletion on Brain Injury after Focal and Global Cerebral Ischemia

“…It has been suggested that PARP-1 and -2 have to act as heterodimers in BER; thus, the absence of one of each would have the same consequence on repair efficiency (Schreiber et al, 2002). However, recent results show that nuclear colocalization of PARP-1 and -2 is low outside the nucleolus, even on stimulation with DNA-damaging agents, supporting the hypothesis that PARP-1 and -2 might have distinct targets and that their heterodimerization might be restricted to the nucleolus (Meder et al, 2005). A double-knockout mouse is not available since the deletion of both PARP-1 and -2 is embryonically lethal (Ménissier de Murcia et al, 2003), but it would be interesting to determine whether our observation can be confirmed by a lack of additional protection in PARP-1 À/À or -2 À/À mice treated with a PARP inhibitor.…”

Enhanced Killing of Cancer Cells by Poly(ADP-ribose) Polymerase Inhibitors and Topoisomerase I Inhibitors Reflects Poisoning of Both Enzymes

“…All images from a single experiment were handled identically. Where indicated, mouse monoclonal anti-C-II-10 anti-PARP1 antibody and Alex Fluor-488-conjugated goat anti-mouse IgG were added to allow simultaneous visualization of PARP1 (76,77) and pADPr.…”

Poly(ADP-ribose) polymerase-2: emerging transcriptional roles of a DNA-repair protein

“…PARP-2 protein can be divided into similar functional regions as PARP-1: The Nterminus of mouse PARP-2 contains the DNA binding domain (DBD), followed by domain E and the catalytic domain (domain F) [8]. The DBD is formed by a SAP domain that is responsible for DNA binding [20], and contains a functional nuclear localization signal (NLS) [21] and a nucleolar localization signal (NoLS) [22]. A caspase-3 cleavage site defines the border between the DBD and domain E, which is homologous to the caspase-3 site in the E domain of PARP-1 [23].…”

“…PARP-2 interacts with topoisomerase I and topoismerase II [40,55] and may thus regulate the rearrangement of DNA structure in conjunction with RNA transcription. Moreover, PARP-2 has been shown to interact with nucleophosmin/B23 [22] that is involved in rRNA transcription [70]. RNA polymerase I inhibition removes PARP-2 from the nucleolus, however the deletion of PARP-2 does not change rRNA expression.…”