The PML nuclear bodies-associated protein TTRAP regulates ribosome biogenesis in nucleolar cavities upon proteasome inhibition

Abstract

TRAF and TNF receptor-associated protein (TTRAP) is a multifunctional protein that can act in the nucleus as a 5 0 -tyrosyl DNA phosphodiesterase and in the cytoplasm as a regulator of cell signaling. In this paper we show that in response to proteasome inhibition TTRAP accumulates in nucleolar cavities in a promyelocytic leukemia protein-dependent manner. In the nucleolus, TTRAP contributes to control levels of ribosomal RNA precursor and processing intermediates, and this phenotype is independent from its 5 0 -tyrosyl DNA phosphodiesterase activity. Our findings suggest a previously unidentified function for TTRAP and nucleolar cavities in ribosome biogenesis under stress. Cell Death and Differentiation (2012) 19, 488-500; doi:10.1038/cdd.2011; published online 16 September 2011 TRAF and TNF receptor-associated protein (TTRAP) is a 5 0 -tyrosyl DNA phosphodiesterase that is required for the repair of topoisomerase2-induced DNA double-strand breaks. 1 It is a member of the endonuclease/exonuclease/ phosphatase family of proteins containing an Mg(2 þ )-dependent apurinic/apyrimidinic endonuclease Ape1-like domain. 2 Various yeast-two hybrid (Y2H) screenings and functional studies have unveiled TTRAP ability to interact with TNF receptors (TNFR) family members and TNFR-associated factors (TRAFs), especially TRAF6. 3 Furthermore, TTRAP was isolated as ETS-associated protein II 4 and as alk4-and smad3-binding protein. 5 Interestingly, TTRAP sequence contains a SUMO-interacting motif (SIM) that is required for its high affinity binding to SUMO-2/3. 6 TTRAP may thus has a role in the cytoplasm as a signaling molecule and in the nucleus as a DNA damage response protein and transcriptional regulator. In this context, its potential interaction with promyelocytic leukemia protein (PML), as previously determined in Y2H, suggests that TTRAP is a PML nuclear bodies (PML-NBs)-associated protein. 7 It remains unclear whether its 5 0 -tyrosyl DNA phosphodiesterase activity may account for all TTRAP biological functions.According to the cellular context, TTRAP may either protect cells from apoptosis or promote death. [8][9][10] When human SH-SY5Y cells are stressed by low doses of proteasome inhibitors, TTRAP is neuroprotective. In these conditions, endogenous TTRAP relocalizes to the cytoplasm and forms aggresome-like inclusions.In this paper we show that in response to high doses of proteasome inhibitors, TTRAP localizes to the nucleolus. This accumulation requires the association to PML-NBs and occurs in nucleolar cavities, a compartment devoid of markers of the 'ribosomal nucleolus'. Lack of TTRAP alters the levels of precursor ribosomal RNA (pre-rRNA) and processing intermediates, suggesting a new role of the PML-NBs-associated protein TTRAP in rRNA biogenesis. This function is dependent on TTRAP SIM motif, but is independent from its 5 0 -tyrosyl DNA phosphodiesterase activity. Altogether, these data suggest a novel function for TTRAP and nucleolar cavities in controlling rRNA biogenesis in response to proteasome inhibiti...

Parkinson's Disease DJ-1 L166P Alters rRNA Biogenesis by Exclusion of TTRAP from the Nucleolus and Sequestration into Cytoplasmic Aggregates via TRAF6

“…This phenotype resembles the one observed in neuroblastoma cells lacking TTRAP expression [20]. Analysis of cell proliferation in untreated and treated conditions could not detect any difference between control and mutant cells (Figure S6).…”

“…Cells were treated with MG132 and rRNA biogenesis was measured by qPCR with A0, 1 and 4 primers as previously described [28], [29], [30] [20]. A scheme of rRNA processing events and positioning of qPCR primers on processing intermediates is shown in figure 3A.…”

Biochemical Characterization of Human Tyrosyl-DNA Phosphodiesterase 2 (TDP2/TTRAP)

“…TDP2 was initially named TTRAP and EAPII because of its role in NF-B (15) and MAPK-ERK (16) signaling transduction, in transcription regulation (17), in zebrafish development (18), and in HIV-1 integration (19). It also promotes cancer cell proliferation (20) and regulates rRNA biogenesis (21). The 5Ј-tyrosyl-DNA phosphodiesterase activity of TDP2 and its function in the repair of trapped topoisomerase II cleavage complexes (12,22) suggests the importance of TDP2 as a target for anticancer therapy.…”

REPA: Applying Pathway Analysis to Genome-Wide Transcription Factor Binding Data

“…A large number of TFs have been implicated in ribosome biogenesis; for instance, roughly 80 factors have been associated in the maturation of the 60S subunit [38]. REPA predicted the following 38 TFs to be associated with the KEGG ribosome pathway (supporting literature is referred to after the corresponding TF): ATF1, ATF2, ATF3, BCL3, BCLAF1, CBX3, CEBPB, CJUN, CREB1 [39], ELF1 [40], ETS1, GABP [41], GR [42], HEY1, IRF3, MTA3, MYBL2, NFATC1, NFIC, NRSF, PML [43], POL2 [37], POU2F2, RFX5, RUNX3, SIN3AK20, SIX5, SP1 [41], SP4, STAT5A, TAF1 [44], TAF7, TBLR1, TCF12, WHIP, YY1 [41], ZNF143, and ZNF263. Thus, we found literature support for 9 (or 24%) of these TFs.…”