TRAF and TNF receptor-associated protein (TTRAP) is a multifunctional protein that can act in the nucleus as a 5'-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'-tyrosyl DNA phosphodiesterase activity. Our findings suggest a previously unidentified function for TTRAP and nucleolar cavities in ribosome biogenesis under stress.
