MKRN3 functions as an E3 ubiquitin ligase that acts as a critical developmental timer controlling the onset of puberty by inhibiting premature activation of the reproductive hormone cascade 1. The protein regulates puberty initiation through multiple mechanisms, including epigenetic regulation of GNRH1 transcription by disrupting MBD3 binding to the GNRH1 promoter through non-proteolytic ubiquitination 2. MKRN3 also modulates GNRH1 mRNA stability and translation by ubiquitinating PABP family members 3. Loss-of-function mutations in MKRN3 cause familial central precocious puberty, characterized by premature activation of the hypothalamic-pituitary-gonadal axis before age 8 in girls and 9 in boys 14. The protein influences hypothalamic development and plasticity, with deletion leading to increased dendritic spines in the arcuate nucleus and early puberty onset 5. MKRN3 targets include neurokinin B and IGF2BP1, through which it regulates prepubertal hypothalamic function 5. Beyond reproductive development, MKRN3 functions as a tumor suppressor in non-small cell lung cancer, regulating cell proliferation through PABPC1 ubiquitination 6. Genetic testing for MKRN3 mutations should be considered in familial cases of central precocious puberty 14.