SAMHD1 is a deoxynucleoside triphosphate triphosphohydrolase that serves dual functions in cellular defense and DNA repair. As a host restriction factor, SAMHD1's dNTPase activity depletes cellular dNTP pools to levels insufficient for retroviral reverse transcription, thereby blocking HIV-1 infection in dendritic and myeloid cells 1. The protein also suppresses LINE-1 retrotransposon activity through this mechanism 2. Beyond antiviral defense, SAMHD1 functions as a critical regulator of DNA replication fork stability during S phase, promoting resection of stalled or reversed replication forks by stimulating MRE11 exonuclease activity and activating the ATR-CHK1 checkpoint pathway 3. This replication fork processing function is essential for preventing chr20 inflammation, as SAMHD1 depletion leads to cytosolic accumulation of single-stranded DNA fragments that activate the cGAS-STING pathway and induce type I interferon production 3. Phosphorylation at Thr-592 acts as a regulatory switch, inhibiting dNTPase activity while promoting DNA end resection functions. SAMHD1 mutations cause Aicardi-Goutières syndrome, a severe inflammatory encephalopathy characterized by elevated interferon signatures 45. Additionally, SAMHD1 dysfunction contributes to NLRP3 inflammasome hyperactivation in obesity through disrupted nucleotide metabolism 6.