Intrinsic disorder in the common N-terminus of human adenovirus 5 E1B-55K and its related E1BN proteins indicated by studies on E1B-93R

The E1B transcription unit of human adenovirus encodes at least five different proteins generated by alternative splicing of a common E1B precursor mRNA. E1B-156R, -93R and -84R contain individual carboxy termini but share a common amino terminus. To acquire data on the structure of the amino terminus we performed biophysical analyses on E1B-93R. We show that E1B-93R is mostly unstructured and fulfills the criteria of an intrinsically disordered protein (IDP). The intrinsic disorder in the amino terminus of these proteins is evolutionary conserved in all seven human adenovirus species. As IDPs comprise a rapidly growing family of proteins which, despite their lack of a well defined structure, often fulfill essential regulatory functions, the observations described here might open up a new avenue for the understanding of the regulation and functions of E1B proteins, in particular the multifunctional E1B-55K oncoprotein.