A Putative Cyclin-binding Motif in Human SAMHD1 Contributes to Protein Phosphorylation, Localization, and Stability.
SAMHD1 (sterile α motif and HD domain-containing protein 1) is a mammalian protein that regulates intracellular dNTP levels through its hydrolysis of dNTPs. SAMHD1 functions as an important retroviral restriction factor through a mechanism relying on its dNTPase activity. We and others have reported that human SAMHD1 interacts with the cell cycle regulatory proteins cyclin A, CDK1, and CDK2, which mediates phosphorylation of SAMHD1 at threonine 592, a post-translational modification that has been implicated in abrogating SAMHD1 restriction function and ability to form stable tetramers. Utilizing co-immunoprecipitation and co-localization approaches, we show that endogenous SAMHD1 is able to interact with the cyclin A-CDK1-CDK2 complexin monocytic THP-1 cells and primary monocyte-derived macrophages. Sequence analysis of SAMHD1 identifies a putative cyclin-binding motif found in many cyclin-CDK complex substrates. Using a mutagenesis-based approach, we demonstrate that the conserved residues in the putative cyclin-binding motif are important for protein expression, protein half-life, and optimal phosphorylation of SAMHD1 at Thr592Furthermore, we observed that SAMHD1 mutants of the cyclin-binding motif mislocalized to a nuclear compartment and had reduced ability to interact with cyclin A-CDK complexes and to form the tetramer. These findings help define the mechanisms by which SAMHD1 is phosphorylated and suggest the contribution of cyclin binding to SAMHD1 expression and stability in dividing cells.
From the Center of Retrovirus Research, Department of Veterinary Biosciences and.
Corine
C
St Gelais
From the Center of Retrovirus Research, Department of Veterinary Biosciences and.
Sun Hee
SH
Kim
the Department of Pediatrics, Emory University, Atlanta, Georgia 30322.
Lingmei
L
Ding
the Department of Microbial Infection and Immunity, Ohio State University, Columbus, Ohio 43210.
Jacob S
JS
Yount
the Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229.
Dmitri
D
Ivanov
the Department of Pediatrics, Emory University, Atlanta, Georgia 30322.|Children's Healthcare of Atlanta, Atlanta, Georgia 30322, and.
Paul
P
Spearman
From the Center of Retrovirus Research, Department of Veterinary Biosciences and wu.840@osu.edu.|the Department of Microbial Infection and Immunity, Ohio State University, Columbus, Ohio 43210.
Li
L
Wu
D016203:CDC2 Protein Kinase; D002455:Cell Division / Q000502:physiology*; D045744:Cell Line, Tumor; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation / Q000502:physiology; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D000076106:SAM Domain and HD Domain-Containing Protein 1
D019925:Cyclin A; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D020559:Monomeric GTP-Binding Proteins
CDK1; CDK2; SAM domain and HD domain-containing protein 1 (SAMHD1); cyclin; cyclin-binding; cyclin-dependent kinase (CDK); phosphorylation; protein stability