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Phosphodiesterase domain of human TDP2, a 5'-tyrosyl DNA phosphodiesterase, and related domains Human TDP2, also known as TTRAP (TRAF/TNFR-associated factors, and tumor necrosis factor receptor/TNFR-associated protein), is a 5'-tyrosyl DNA phosphodiesterase. It is required for the efficient repair of topoisomerase II-induced DNA double strand breaks. The topoisomerase is covalently linked by a phosphotyrosyl bond to the 5'-terminus of the break. TDP2 cleaves the DNA 5'-phosphodiester bond and restores 5'-phosphate termini, needed for subsequent DNA ligation, and hence repair of the break. TDP2 and 3'-tyrosyl DNA phosphodiesterase (TDP1) are complementary activities; together, they allow cells to remove trapped topoisomerase from both 3'- and 5'-DNA termini. TTRAP has been reported as being involved in apoptosis, embryonic development, and transcriptional regulation, and it may inhibit the activation of nuclear factor-kB. This family belongs to the large EEP (exonuclease/endonuclease/phosphatase) superfamily that contains functionally diverse enzymes that share a common catalytic mechanism of cleaving phosphodiester bonds.
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