INI1SNF5

INI1SNF5, also known as INI1 (hSNF5), SMARCB1, or BAF47, is a protein encoded by the SMARCB1 gene in humans. It functions as a core subunit of the SWI/SNF chromatin remodeling complex, which modulates nucleosome positioning to regulate transcription. The protein contains an acidic domain, a conserved histone-fold motif, and a C‑terminal leucine‑zipper‑like region that mediates interactions with other SWI/SNF components. As part of the complex, INI1SNF5 contributes to the deposition of histone H2A/H2B dimers and facilitates access to DNA by transcription factors.

Loss or mutation of SMARCB1 is a hallmark of atypical teratoid/rhabdoid tumors (AT/RT) in the central nervous system and a subset of malignant rhabdoid tumors of the kidney, kidney, and soft tissues. Germline or somatic bi‑allelic inactivation leads to a failure of chromatin remodeling and uncontrolled cell proliferation. In addition to cancer, heterozygous variants of SMARCB1 have been implicated in several developmental disorders, such as Gopalman syndrome and schwannomatosis.

The gene is located on chromosome 22q11.23 and spans 9.3 kilobases of DNA. It consists of 20 exons, producing a protein of 425 amino acids. INI1SNF5 is ubiquitously expressed, with higher levels in the brain, kidney, and testis. Its expression is tightly regulated during development, and disruptions of the normal expression pattern are associated with oncogenesis. The protein has been shown to interact with INI2, ARID1A, and BRG1, stabilizing the SWI/SNF complex. Therapeutic strategies targeting the downstream effects of SMARCB1 loss, such as EZH2 inhibition, are under investigation for tumors that harbor INI1SNF5 defects.