7LTT

SAMHD1(113-626) H206R D207N R366C

Summary for 7LTT

• Entry DOI: 10.2210/pdb7ltt/pdb
• Descriptor: Deoxynucleoside triphosphate triphosphohydrolase SAMHD1, 2'-DEOXYGUANOSINE-5'-TRIPHOSPHATE, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: dntpase, tetramer, mutant, cancer, hydrolase
• Biological source: Homo sapiens (Human)
• Total number of polymer chains: 4
• Total formula weight: 251565.42

Authors

Temple, J.T.,Bowen, N.E. (deposition date: 2021-02-20, release date: 2021-11-24, Last modification date: 2024-10-23)

Primary citation

Bowen, N.E.,Temple, J.,Shepard, C.,Oo, A.,Arizaga, F.,Kapoor-Vazirani, P.,Persaud, M.,Yu, C.H.,Kim, D.H.,Schinazi, R.F.,Ivanov, D.N.,Diaz-Griffero, F.,Yu, D.S.,Xiong, Y.,Kim, B.
Structural and functional characterization explains loss of dNTPase activity of the cancer-specific R366C/H mutant SAMHD1 proteins.
J.Biol.Chem., 297:101170-101170, 2021

PubMed Abstract: Elevated intracellular levels of dNTPs have been shown to be a biochemical marker of cancer cells. Recently, a series of mutations in the multifunctional dNTP triphosphohydrolase (dNTPase), sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1), have been reported in various cancers. Here, we investigated the structure and functions of SAMHD1 R366C/H mutants, found in colon cancer and leukemia. Unlike many other cancer-specific mutations, the SAMHD1 R366 mutations do not alter cellular protein levels of the enzyme. However, R366C/H mutant proteins exhibit a loss of dNTPase activity, and their X-ray structures demonstrate the absence of dGTP substrate in their active site, likely because of a loss of interaction with the γ-phosphate of the substrate. The R366C/H mutants failed to reduce intracellular dNTP levels and restrict HIV-1 replication, functions of SAMHD1 that are dependent on the ability of the enzyme to hydrolyze dNTPs. However, these mutants retain dNTPase-independent functions, including mediating dsDNA break repair, interacting with CtIP and cyclin A2, and suppressing innate immune responses. Finally, SAMHD1 degradation in human primary-activated/dividing CD4+ T cells further elevates cellular dNTP levels. This study suggests that the loss of SAMHD1 dNTPase activity induced by R366 mutations can mechanistically contribute to the elevated dNTP levels commonly found in cancer cells.

PubMed: 34492268
DOI: 10.1016/j.jbc.2021.101170

Experimental method

X-RAY DIFFRACTION (1.9 Å)