Intermediate filament and related proteins: potential activators of nucleosomes during transcription initiation and...

Intermediate filament (IF) protein tetramers contain two DNA- and core-histone-binding motifs in rotational symmetry in one and the same structural entity. We propose that IF protein oligomers might displace histone octamers from nucleosomes in the process of transcription initiation and elongation, to deposit them transiently on their alpha-helical coiled-coil domains. We further propose that structurally related proteins of the karyoskeleton, constructed from an alpha-helical domain capable of coiled-coil formation and a basic DNA-binding region adjacent to it, may be similarly involved in nucleosome activation. These proteins would function as auxiliary factors that disrupt nucleosomal structure to permit transcription and other DNA-dependent processes to proceed expiditiously.