Transcription factor nuclear factor I proteins form stable homo- and heterodimers.

Nuclear factor I (NFI) proteins constitute a large family of eukaryotic DNA binding proteins. They are involved in viral and cellular aspects of transcriptional regulation and they are capable of stimulating adenovirus initiation of replication. Using in vitro translated NFI proteins encoded by four different chicken NFI genes, we have detected homodimers as well as heterodimers for all combinations tested. The formation of heterodimers was critically dependent on cotranslation, indicating stable dimer formation in the absence of DNA. The unrestricted heterodimerization of NFI proteins adds, beside gene diversity and alternative splicing, another level of diversity to this protein family.