What are the normal biological functions of low complexity amino acid sequences including poly-glutamines?

Low complexity sequences - repeats that use only a subset of amino acids – are very abundant but their role is only beginning to be defined.  The set of proteins involved in transcription is highly enriched for low complexity sequences (LCS) in all Eukaryotes.  Chromosomal rearrangements involving LCS are causative of transformation in several cancers, notably sarcomas, demonstrating their powerful regulatory potential. Therefore, we have begun to investigate the biological functions of low complexity sequences in transcriptional control. We are focusing on the SWI/SNF chromatin-remodeling complex, which contains a large number of low complexity subunits including four polyglutamine (polyQ) domains.