Contribution of oligomerization to the anti-HIV-1 properties of SAMHD1.
BACKGROUND
SAMHD1 is a restriction factor that potently blocks infection by HIV-1 and other retroviruses. We have previously demonstrated that SAMHD1 oligomerizes in mammalian cells by immunoprecipitation. Here we investigated the contribution of SAMHD1 oligomerization to retroviral restriction.


RESULTS
Structural analysis of SAMHD1 and homologous HD domain proteins revealed that key hydrophobic residues Y146, Y154, L428 and Y432 stabilize the extensive dimer interface observed in the SAMHD1 crystal structure. Full-length SAMHD1 variants Y146S/Y154S and L428S/Y432S lost their ability to oligomerize tested by immunoprecipitation in mammalian cells. In agreement with these observations, the Y146S/Y154S variant of a bacterial construct expressing the HD domain of human SAMHD1 (residues 109-626) disrupted the dGTP-dependent tetramerization of SAMHD1 in vitro. Tetramerization-defective variants of the full-length SAMHD1 immunoprecipitated from mammalian cells and of the bacterially-expressed HD domain construct lost their dNTPase activity. The nuclease activity of the HD domain construct was not perturbed by the Y146S/Y154S mutations. Remarkably, oligomerization-deficient SAMHD1 variants potently restricted HIV-1 infection.


CONCLUSIONS
These results suggested that SAMHD1 oligomerization is not required for the ability of the protein to block HIV-1 infection.
Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1301 Morris Park - Price Center 501, Bronx, NY 10461, USA. Felipe.Diaz-Griffero@einstein.yu.edu.
Alberto
A
Brandariz-Nuñez
Jose Carlos
JC
Valle-Casuso
Tommy E
TE
White
Laura
L
Nguyen
Akash
A
Bhattacharya
Zhonghua
Z
Wang
Borries
B
Demeler
Sarah
S
Amie
Caitlin
C
Knowlton
Baek
B
Kim
Dmitri N
DN
Ivanov
Felipe
F
Diaz-Griffero
D002460:Cell Line; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D015497:HIV-1 / Q000276:immunology*; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D008958:Models, Molecular; D020559:Monomeric GTP-Binding Proteins / Q000276:immunology* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D000076106:SAM Domain and HD Domain-Containing Protein 1
D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D020559:Monomeric GTP-Binding Proteins