SP5 is a transcription factor that binds GC-box promoter elements and functions as a transcriptional activator with roles in embryonic pattern formation. SP5 operates as a DNA-binding transcription factor regulating RNA polymerase II-dependent transcription 1. SP5 plays a critical role in primary cilia formation in mammalian embryos. Conditional genetic studies in mice demonstrate that SP5, together with SP8, regulates cilia formation and associated gene expression 2. In Sp5/Sp8 mutant embryos, primary and motile cilia are shorter than normal and reduced in number across cell types, resulting in situs inversus and hydrocephalus phenotypes 3. Notably, SP8 expression is sufficient to induce primary cilia formation in previously unciliated cells 2. SP5 functions as a Wnt pathway component and target gene downstream of β-catenin signaling 1. Recent evidence reveals that SP5 acts as a transcriptional regulator at clustered R-loops at gene promoters, where it recruits zinc-finger proteins and enhances transcription in a cluster-dependent manner 4. Additionally, SP5 regulates SERPING1 transcription by binding its promoter, driving SERPING1-mediated suppression of lung adenocarcinoma progression through the TSC2/mTOR pathway 5. These findings establish SP5 as a multifunctional transcriptional regulator with significance in developmental organogenesis, ciliogenesis, and cancer biology.