Nuclear Factor I/B (NFIB)

Liu et al. (1997) cloned and characterized 3 splice variants of NFIB. NFIB1 and NFIB2 are translated from an 8.7-kb message that encodes proteins containing an N-terminal DNA-binding domain and a C-terminal transactivation domain. NFIB3 is a truncated 188-amino acid protein, translated from a 1.8-kb message, that contains only the N-terminal DNA-binding domain. Northern blot analysis detected the 1.8-kb NFIB3 message in HeLa cells and fibroblasts, as well as in several human tissue samples. Coexpression of NFIB3 with active isoforms of NFIB, NFIC, and NFIX, however, led to a strong repression of transcription by the other NFI proteins. Gel shift analysis indicated that NFIB3 formed heterodimers with the other NFI proteins and reduced their ability to bind DNA.