Zinc Ions Modulate YY1 Activity: Relevance in Carcinogenesis.

YY1 is widely recognized as an intrinsically disordered transcription factor that plays a role in development of many cancers. In most cases, its overexpression is correlated with tumor progression and unfavorable patient outcomes. Our latest research focusing on the role of zinc ions in modulating YY1's interaction with DNA demonstrated that zinc enhances the protein's multimeric state and affinity to its operator. In light of these findings, changes in protein concentration appear to be just one element relevant to modulating YY1-dependent processes. Thus, alterations in zinc ion concentration can directly and specifically impact the regulation of gene expression by YY1, in line with reports indicating a correlation between zinc ion levels and advancement of certain tumors. This review concentrates on other potential consequences of YY1 interaction with zinc ions that may act by altering charge distribution, conformational state distribution, or oligomerization to influence its interactions with molecular partners that can disrupt gene expression patterns.

Site-directed fluorescence labeling of intrinsically disordered region of human transcription factor YY1: The inhibitory effect of zinc ions.

Site-specific labeling of proteins with fluorescent dyes allows the study of protein structure and function using a wide variety of fluorescent techniques. However, specific labeling is not trivial in the case of proteins containing multiple cysteine residues. An example of such a protein is transcription factor Yin Yang 1, which comprises eight cysteine residues in four C2H2 type zinc fingers in the C-terminal region. Kinetic measurements of the labeling process allowed us to develop preparative labeling of three cysteine residues differently introduced to the N-terminal, disordered fragment of the protein. The protocol developed in the present study allows to prepare the protein with high recovery yield and high selectivity of the labeling. This was confirmed using proteolytic digestion and spectroscopic approach. The labeling process was significantly affected by the presence of zinc ions and was dependent on the localization of the engineered cysteine residue. This is the first known example of the use of cysteine metal protection and labeling (CyMPL) technology for the labeling of protein regions with no stable secondary structures.

Intrinsic disorder of human Yin Yang 1 protein.

YY1 (Yin Yang 1) is a zinc finger protein with an essential role in various biological functions via DNA- and protein-protein interactions with numerous partners. YY1 is involved in the regulation of a broad spectrum of cellular processes such as embryogenesis, proliferation, tumorigenesis, and snRNA transcription. The more than 100 reported targets of the YY1 protein suggest that it contains intrinsically disordered regions that are involved in such diverse interactions. Here, we present a study of the structural properties of human YY1 using several biochemical and biophysical techniques (fluorescence, circular dichroism, gel filtration chromatography, proteolytic susceptibility) together with various bioinformatics approaches. To facilitate our exploration of the YY1 structure, the full-length protein as well as an N-terminal fragment (residues 1-295) and the C-terminal DNA binding domain were used. We found the N-terminus to be a non-compact fragment of YY1 with little residual secondary structure and lacking a well-defined tertiary structure. The results of our study indicate that YY1 belongs to the family of intrinsically disordered proteins (IDPs), which exist natively in a partially unfolded conformation.