Single-Stranded Nucleic Acids Bind to the Tetramer Interface of SAMHD1 and Prevent Formation of the Catalytic Homotetramer
| Autor: | James T. Stivers, Namandjé N. Bumpus, Kyle J. Seamon |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
DNA Single-Stranded Biology Biochemistry Catalysis Mass Spectrometry Article Nucleic acid metabolism SAM Domain and HD Domain-Containing Protein 1 03 medical and health sciences chemistry.chemical_compound Biopolymers Humans Binding site Cloning Molecular Monomeric GTP-Binding Proteins Oligonucleotide 030104 developmental biology chemistry Bromodeoxyuridine Nucleic acid RNA HD domain Sterile alpha motif DNA Homotetramer Chromatography Liquid |
| Zdroj: | Biochemistry. 55(44) |
| ISSN: | 1520-4995 |
| Popis: | Sterile alpha motif and HD domain protein 1 (SAMHD1) is a unique enzyme that plays important roles in nucleic acid metabolism, viral restriction, and the pathogenesis of autoimmune diseases and cancer. Although much attention has been focused on its dNTP triphosphohydrolase activity in viral restriction and disease, SAMHD1 also binds to single-stranded RNA and DNA. Here we utilize a UV cross-linking method using 5-bromodeoxyuridine-substituted oligonucleotides coupled with high-resolution mass spectrometry to identify the binding site for single-stranded nucleic acids (ssNAs) on SAMHD1. Mapping cross-linked amino acids on the surface of existing crystal structures demonstrated that the ssNA binding site lies largely along the dimer-dimer interface, sterically blocking the formation of the homotetramer required for dNTPase activity. Surprisingly, the disordered C-terminus of SAMHD1 (residues 583-626) was also implicated in ssNA binding. An interaction between this region and ssNA was confirmed in binding studies using the purified SAMHD1 583-626 peptide. Despite a recent report that SAMHD1 possesses polyribonucleotide phosphorylase activity, we did not detect any such activity in the presence of inorganic phosphate, indicating that nucleic acid binding is unrelated to this proposed activity. These data suggest an antagonistic regulatory mechanism in which the mutually exclusive oligomeric state requirements for ssNA binding and dNTP hydrolase activity modulate these two functions of SAMHD1 within the cell. |
| Databáze: | OpenAIRE |
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