Structural Investigations of the Nickel-Induced Inhibition of Truncated Constructs of the JMJD2 Family of Histone Demethylases Using X-ray Absorption Spectroscopy

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• 作者：Nitai Charan Giri ; Lisa Passantino ; Hong Sun ; Maria Antonietta Zoroddu ; Max Costa ; Michael J. Maroney
• 刊名：Biochemistry
• 出版年：2013
• 出版时间：June 18, 2013
• 年：2013
• 卷：52
• 期：24
• 页码：4168-4183
• 全文大小：591K
• 年卷期：v.52,no.24(June 18, 2013)
• ISSN：1520-4995

文摘

Occupational and/or environmental exposure to nickel has been implicated in various types of cancer, and in vitro exposure to nickel compounds results in the accumulation of Ni(II) ions in cells. One group of major targets of Ni(II) ions inside the cell consists of Fe(II)- and 伪KG-dependent dioxygenases. Using JMJD2A and JMJD2C as examples, we show that the JMJD2 family of histone demethylases, which are products of putative oncogenes as well as Fe(II)- and 伪KG-dependent dioxygenases, are highly sensitive to inhibition by Ni(II) ions. In this work, X-ray absorption spectroscopy (XAS) has been used to investigate the Fe(II) active site of truncated JMJD2A and JMJD2C (1鈥?50 amino acids) in the presence and absence of 伪KG and/or substrate to obtain mechanistic details of the early steps in catalysis that precede O₂ binding in histone demethylation by the JMJD2 family of histone demethylases. Zinc K-edge XAS has been performed on the resting JMJD2A (with iron in the active site) to confirm the presence of the expected structural zinc site. XAS of the Ni(II)-substituted enzymes has also been performed to investigate the inhibition of these enzymes by Ni(II) ions. Our XAS results indicate that the five-coordinate Fe(II) center in the resting enzyme is retained in the binary and ternary complexes. In contrast, the Ni(II) center is six-coordinate in the resting enzyme and binary and ternary complexes. XAS results indicate that both Fe(II) and Ni(II) bind 伪KG in the binary and ternary complexes. The electron density buildup that is observed at the Fe(II) center in the presence of 伪KG and substrate is not observed at the Ni(II) center. Thus, both electronic and steric factors are responsible for Ni-induced inhibition of the JMJD2 family of histone demethylases. Ni-induced inhibition of these enzymes may explain the alteration of the epigenetic mechanism of gene expression that is responsible for Ni-induced carcinogenesis.