SAM domain and HD domain-containing protein 1 (SAMHD1)

SAM domain and HD domain-containing protein 1 (SAMHD1) is a critical regulator of intracellular deoxynucleoside triphosphate (dNTP) levels, functioning as a dNTP triphosphohydrolase (Goldstone et al., 2011). The enzyme's catalytic activity is strictly controlled by two allosteric sites: Allosteric Site 1 (A1), which specifically binds GTP or dGTP, and Allosteric Site 2 (A2), which binds various dNTPs (Ji et al., 2013). The binding of dGTP to these sites is essential for the formation of the active tetrameric state of the enzyme, which then proceeds to hydrolyze dNTPs into deoxynucleosides and inorganic triphosphate. In oncology, SAMHD1 is a major determinant of sensitivity to nucleoside analog therapies, such as cytarabine (Ara-C), because it can hydrolyze the active triphosphate forms of these drugs, leading to chemoresistance (Schneider et al., 2017). Additionally, SAMHD1 serves as an innate immune factor that restricts the replication of retroviruses like HIV-1 by depleting the dNTP pools necessary for reverse transcription (Hrecka et al., 2011). Mutations that abolish SAMHD1 function are linked to Aicardi-Goutières syndrome, an autoinflammatory disorder characterized by an inappropriate interferon response to endogenous nucleic acids (Rice et al., 2009).

Other names

SAM domain and HD domain-containing protein 1Monocyte protein 5MOP-5DCIPHDDC1dNTP triphosphohydrolase SAMHD1dGTP-binding sites of SAMHD1

SAMHD1 functions as a dNTP triphosphohydrolase that is allosterically activated by the binding of dGTP (or GTP) to its allosteric sites, which induces the formation of a catalytically active tetramer. Drugs targeting this protein typically act as substrates that are degraded by the enzyme (leading to resistance) or as potential inhibitors designed to prevent the breakdown of therapeutic nucleoside analog triphosphates.