Controlling gene expression through five zinc finger domains of <scp>ZNF18</scp>

Zinc finger (ZF) proteins are the most abundant transcription factors in vertebrates, and they regulate gene expression through interactions with cis-acting elements. ZF domains selectively recognize specific sequences to accelerate or repress target genes. Zinc finger protein 18 (ZNF18) contains five CX₂CX₁₂HX₃H-type ZFs at the C-terminus, which are expressed in the brain and other organs of the biological system. Bioinformatic study proposed that cyclin-dependent kinase 1 (CDK1) is in the signaling cascade of ZNF18; although experimental evidence has not yet been reported. In this study, we expressed and purified ZNF18(ZF1-5), five ZF domains from ZNF18, and investigated metal binding specificity and promoter interactions. ZNF18(ZF1-5) has specific coordination to Zn²⁺ (K_d ≤ 18 nM) compared with other xenobiotic metal ions, including Co²⁺, Fe²⁺, and Fe³⁺, with 98.5% of reduced ZF domains after purification. This significantly active ZF can be one of the major reasons for tight coordination affinity. CDK1 rescued the arrested cell cycle induced by DNA damage, resulting in tumorigenesis. Zn²⁺-ZNF18(ZF1-5) specifically binds to cis-acting elements of cdk1 (K_d = 4.63 ± 0.07 nM), mediated by a cell cycle-dependent element (cde, 5'-CGCGG) and a cell cycle gene homology region (chr, 5'-TTGAA). The ZNF18 superfamily was expressed in the brain for the regulation of neuronal development and cell differentiation. Zn²⁺-ZNF18(ZF1-5) interacted with promoters in the insulin response sequence (IRS) for inhibition of dopamine secretion and cis-acting element of brain-2 (BRN2), which controlled astrocyte and cancer development. These results provide the first evidence that ZNF18(ZF1-5) regulates the cell cycle and neuronal development through transcriptional regulation.