[^1]
| Symbol |
SAMHD1 |
| Full Name |
SAM and HD Domain Containing Metal Dependent Hydrolase 1 |
| Chromosome |
20q11.23 |
| NCBI Gene |
9833 |
| Ensembl |
ENSG00000101347 |
| OMIM |
606754 |
| UniProt |
Q9Y3D9 |
| Diseases |
[Aicardi-Goutieres Syndrome](/diseases/aicardi-goutieres-syndrome), [Chronic Lymphocytic Leukemia](/diseases/chronic-lymphocytic-leukemia), [HIV Infection](/diseases/hiv) |
| Expression |
Ubiquitously expressed; high expression in brain, hematopoietic cells |
¶ SAMHD1 — SAM and HD Domain Containing Metal Dependent Hydrolase 1
SAMHD1 (SAM and HD Domain Containing Metal Dependent Hydrolase 1) is a gene located on chromosome 20q11.23 that encodes a dNTP triphosphohydrolase enzyme with important roles in innate immunity and DNA repair. SAMHD1 is best known for its ability to restrict HIV and other retroviruses by depleting the cellular dNTP pool, making it a critical component of the innate immune system. Mutations in SAMHD1 cause Aicardi-Goutieres syndrome (AGS) and are associated with increased cancer risk [1][2].
The SAMHD1 gene spans approximately 40 kb and consists of 20 exons. The gene encodes a 626-amino acid protein with enzymatic activity.
- Chromosome: 20q11.23
- Location: chr20: 35020647-35061126
- Strand: Plus strand
- Exons: 20
¶ Protein Structure and Function
¶ Domain Architecture
SAMHD1 contains:
- N-terminal SAM domain: Protein-protein interactions
- HD domain: Catalytic center with metal-dependent hydrolase activity
- C-terminal region: Regulatory elements
SAMHD1 functions as a dNTP triphosphohydrolase:
- Hydrolyzes dNTPs to deoxynucleosides and triphosphates
- Requires Mg2+ or Mn2+ for catalysis
- Tetramerization is required for activity
- Regulated by phosphorylation at Thr592
- Retroviral restriction: Depletes dNTP pool to block viral replication
- Interferon response: Induced by type I interferon signaling
- Pattern recognition: Detects foreign nucleic acids
- dNTP homeostasis: Maintains cellular dNTP levels
- DNA repair: Supports DNA repair processes
- Cell cycle regulation: Controls dNTP availability during S phase
SAMHD1 mutations account for approximately 10% of AGS cases. Clinical features include:
- Progressive encephalopathy
- Intracranial calcifications
- Leukodystrophy
- Elevated interferon signature
- Chilblain lupus-like skin lesions
Pathogenic variants:
- Missense mutations (D208N, R145H, Q83X)
- Frameshift and nonsense mutations
- Splice-site mutations
SAMHD1 is a tumor suppressor:
- Loss-of-function increases cancer risk
- Associated with chronic lymphocytic leukemia (CLL)
- Mutations found in various malignancies
SAMHD1 restricts HIV-1 infection in:
- Myeloid cells (macrophages, dendritic cells)
- Resting CD4+ T cells
- Microglial cells
SAMHD1 is ubiquitously expressed with highest levels in:
- Brain (neurons, microglia)
- Hematopoietic cells (monocytes, macrophages)
- Spleen
- Lymph nodes
- Bone marrow
- Cytoplasmic and nuclear localization
- Associates with chromatin
- Nuclear import signals
SAMHD1 expression is regulated by:
- Type I and II interferon signaling
- Cell cycle (cell cycle-dependent phosphorylation)
- DNA damage responses
- SAMHD1-targeting: Understanding its restriction mechanism informs HIV therapy
- Therapeutic modulation: Exploring strategies to modulate SAMHD1 activity
- SAMHD1 loss increases sensitivity to some chemotherapies
- dNTP pool modulation as cancer treatment strategy
- JAK inhibitors to suppress interferon signature
- Supportive neurological care
- SAMHD1 mutations cause Aicardi-Goutieres syndrome. Nature Genetics, 2012.
- SAMHD1 is a retroviral restriction factor. Cell, 2011.
- SAMHD1 dNTPase: structure and mechanism. Journal of Biological Chemistry, 2014.