NF-KAPPA-B MEDIATED TRANSCRIPTIONAL ACTIVATION IS ENHANCED BY THE ARCHITECTURAL FACTOR HMGI-C

High mobility group I proteins (HMGI, HMGY and HMGI-C) are a family of low molecular mass non-histone nuclear proteins which constitute an i mportant component of the active chromatin structure, Two members of t his family, HMGI and HMGY, have been demonstrated to contribute to the transcriptional regulation of several promoters by interacting with t he DNA and with different transcription factors, On the contrary, very little is known about the third member, HMGI-C, which plays an import ant role during embryonic growth and in the process of cell transforma tion, its gene being rearranged in a large number of mesenchimal tumor s, In this paper we show for the first time that HMGI-C is also able t o function as architectural factor, enhancing the activity of a transc ription factor, NF-KB, through the PRDII element of the beta-interfero n enhancer, Moreover we show that this enhancement is absolutely depen dent on the binding of HMGI-C to its target sequence. The demonstratio n that HMGI-C is able to modulate transcription is thus an important i nitial step in the identification of genes regulated by this factor.