Cross-β Polymerization of Low Complexity Sequence Domains

Most transcription factors and RNA regulatory proteins encoded by eukaryotic genomes ranging from yeast to humans contain polypeptide domains variously described as intrinsically disordered, prion-like, or of low complexity (LC). These LC domains exist in an unfolded state when DNA and RNA regulatory proteins are studied in biochemical isolation from cells. Upon incubation in the purified state, many of these LC domains polymerize into homogeneous, labile amyloid-like fibers. Here, we consider several lines of evidence that may favor biologic utility for LC domain polymers.