Chemoproteomic Approach for Identifying Nuclear Arsenite-Binding Proteins

Trivalent arsenic, i.e., As(III), is the main form of
arsenic species
in the environment. Prolonged exposure to arsenicals through ingesting
contaminated food and water has been implicated in the development
of cancer and diabetes as well as cardiovascular and neurodegenerative
diseases. A number of studies have been conducted to examine the mechanisms
underlying the toxic effects of arsenite exposure, where As(III) was
shown to displace Zn(II) and impair the functions of zinc-binding
proteins. Considering that many zinc-binding proteins can bind to
nucleic acids, we reason that systematic identification of arsenite-binding
proteins in the nucleus may provide additional insights into the molecular
targets of arsenite, thereby improving our understanding of the mechanisms
of arsenic toxicity. Here, we conducted a quantitative proteomics
experiment relying on affinity pull-down from nuclear protein lysate
with a biotin-As(III) probe to identify nuclear arsenite-binding proteins.
We uncovered a number of candidate As(III)-binding proteins that are
involved in mRNA splicing, DNA repair, and replication. We also found
that As(III) could bind to splicing factor 1 (SF1) and that this binding
perturbs mRNA splicing in human cells. Together, our work provided
insights into the mechanisms of As(III) toxicity by revealing new
nuclear protein targets of As(III).