Cold-Shock Domains—Abundance, Structure, Properties, and Nucleic-Acid Binding

SIMPLE SUMMARY: Proteins are composed of compact domains, often of known three-dimensional structure, and natively unstructured polypeptide regions. The abundant cold-shock domain is among the set of canonical nucleic acid-binding domains and conserved from bacteria to man. Proteins containing cold-shock domains serve a large variety of biological functions, which are mostly linked to DNA or RNA binding. These functions include the regulation of transcription, RNA splicing, translation, stability and sequestration. Cold-shock domains have a simple architecture with a conserved surface ideally suited to bind single-stranded nucleic acids. Because the binding is mostly by non-specific molecular interactions which do not involve the sugar-phosphate backbone, cold-shock domains are not strictly sequence-specific and do not discriminate reliably between DNA and RNA. Many, but not all functions of cold shock-domain proteins in health and disease can be understood based of the physical and structural properties of their cold-shock domains. ABSTRACT: The cold-shock domain has a deceptively simple architecture but supports a complex biology. It is conserved from bacteria to man and has representatives in all kingdoms of life. Bacterial cold-shock proteins consist of a single cold-shock domain and some, but not all are induced by cold shock. Cold-shock domains in human proteins are often associated with natively unfolded protein segments and more rarely with other folded domains. Cold-shock proteins and domains share a five-stranded all-antiparallel β-barrel structure and a conserved surface that binds single-stranded nucleic acids, predominantly by stacking interactions between nucleobases and aromatic protein sidechains. This conserved binding mode explains the cold-shock domains’ ability to associate with both DNA and RNA strands and their limited sequence selectivity. The promiscuous DNA and RNA binding provides a rationale for the ability of cold-shock domain-containing proteins to function in transcription regulation and DNA-damage repair as well as in regulating splicing, translation, mRNA stability and RNA sequestration.