Mechanisms of inhibition of zinc-finger transcription factors by selenium compounds ebselen and selenite.
The anti-inflammatory selenium compounds, ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) and selenite, were found to alter the DNA binding mechanisms and structures of cysteine-rich zinc-finger transcription factors. As assayed by DNase I protection, DNA binding by TFIIIA (transcription factor IIIA, prototypical Cys(2)His(2) zinc finger protein), was inhibited by micromolar amounts of ebselen. In a gel shift assay, ebselen inhibited the Cys(2)His(2) zinc finger-containing DNA binding domain (DBD) of the NF-kappaB mediated transcription factor Sp1. Ebselen also inhibited DNA binding by the p50 subunit of the pro-inflammatory Cys-containing NF-kappaB transcription factor. Electrospray ionization mass spectrometry (ESI-MS) was utilized to elucidate mechanisms of chemical interaction between ebselen and a zinc-bound Cys(2)His(2) zinc finger polypeptide modeled after the third finger of Sp1 (Sp1-3). Exposing Sp1-3 to micromolar amounts of ebselen resulted in Zn(2+) release from this peptide and the formation of a disulfide bond by oxidation of zinc finger SH groups, the likely mechanism for DNA binding inhibition. Selenite was shown by ESI-MS to also eject zinc from Sp1-3 as well as induce disulfide bond formation through SH oxidation. The selenite-dependent inhibition/oxidation mechanism differed from that of ebselen by inducing the formation of a stable selenotrisulfide bond. Selenite-induced selenotrisulfide formation was dependent upon the structure of the Cys(2)His(2) zinc finger as alteration in the finger structure enhanced this reaction as well as selenite-dependent zinc release. Ebselen and selenite-dependent inhibition/oxidation of Cys-rich zinc finger proteins, with concomitant release of zinc and finger structural changes, points to mechanisms at the atomic and protein level for selenium-induced alterations in Cys-rich proteins, and possible amelioration of certain inflammatory, neurodegenerative, and oncogenic responses.
Larabee
Jason L
JL
Department of Biochemistry and Molecular Biology, University of Oklahoma College of Medicine, 940 Stanton Young Blvd., Room 939, Oklahoma City, OK 73104, United States.
Hocker
James R
JR
Hanas
Jay S
JS
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001393:Azoles / Q000378:metabolism / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism; D005260:Female; D006801:Humans; D054833:Isoindoles; D016566:Organoselenium Compounds / Q000378:metabolism / Q000494:pharmacology*; D010053:Ovary; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018038:Sodium Selenite / Q000378:metabolism / Q000494:pharmacology*; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D035582:Transcription Factor TFIIIA / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014982:Xenopus laevis; D016335:Zinc Fingers / Q000187:drug effects*; D000097782:NF-kappaB-Inducing Kinase
D000894:Anti-Inflammatory Agents, Non-Steroidal; D001393:Azoles; D004247:DNA; D054833:Isoindoles; D016566:Organoselenium Compounds; D017346:Protein Serine-Threonine Kinases; D018038:Sodium Selenite; D016329:Sp1 Transcription Factor; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D000097782:NF-kappaB-Inducing Kinase; C042986:ebselen