NICN1 (nicolin 1, tubulin polyglutamylase complex subunit) is a mammalian-specific nuclear protein of 213 amino acids that does not belong to any known protein family 1. It localizes to the nucleoplasm and exhibits tissue-specific expression patterns, with highest levels in brain, testis, liver, and kidney 1. NICN1 functions as a host factor promoting HIV-1 latency; its downregulation significantly enhances HIV-1 gene expression in CD4+ T cells by stimulating RNA Polymerase II-mediated transcription 2. Recent CRISPR screening identified NICN1 among novel host factors associated with HIV-1 latency maintenance 3. Beyond virology, NICN1 expression correlates with the tumor suppressor FHIT in both lung adenocarcinoma and squamous cell carcinoma, suggesting potential involvement in cancer-related pathways 4. Genetic association studies link NICN1 to sedentary behavior-related obesity risk, with eQTL analysis revealing its involvement in hormonal and metabolic pathways including cortisol synthesis, thyroid hormone synthesis, and insulin secretion in adipose tissues 5. NICN1 is positioned immediately upstream of the aminomethyltransferase gene in the genome 6.