H₂S-Mediated Persulfidation of the Classical Zinc Finger Protein Yin-Yang 1

Yin-Yang 1 (YY1) is a CCHH-type classical zinc finger (ZF) protein that plays diverse roles in gene expression, acting as both a transcriptional activator and repressor, which is important for DNA repair, neuronal development, and oncogenesis. Classical ZFs adopt a ββα fold upon Zn(II) binding, and YY1 contains four CCHH-type domains. The two central domains (ZF2 and ZF3) are known to directly bind to DNA. Although ZFs have traditionally been viewed as just structural domains, emerging data shows that ZFs can be modified by the gaseous signaling molecule hydrogen sulfide, H₂S, to form persulfides. These data are principally from proteomics studies from which several classical ZFs, including YY1, were identified as persulfidated. Herein, we report how the classical ZF YY1 is persulfidated by H₂S and the effects of persulfidation on DNA binding using three ZF constructs containing the second domain (YY1-ZF2), third domain (YY1-ZF3), and both the second and third domains (YY1-ZF2-ZF3). Persulfidation of all three constructs was observed using an NBF-Cl/dimedone tag-switch method. Persulfidation required Zn(II) and O₂. Superoxide, as measured by hydroethidine and superoxide dismutase experiments, was also observed as an intermediate. YY1-ZF2-ZF3 was also shown to bind to the adeno-associated virus P5 initiator and IL-6 promoter DNA via a fluorescence anisotropy assay. This ZF/DNA binding was abrogated by H₂S; however, when DNA was bound to YY1-ZF2-ZF3, it was unreactive to H₂S modification suggesting a protective effect of the DNA macromolecule. In addition, H₂S disrupted the secondary structure of all three YY1 constructs as measured by circular dichroism.