The Evolutionary Genomics group of GRIB (UPF – IMIM), http://evolutionarygenomics.imim.es led by Mar Albà, has published at the Journal Genome Research a study that shows, using a comparative genomics approach, that many more amino acid tandem repeats in human proteins than previously suspected are likely to be functional. The main novelty of this study is the comparison of the degree of conservation of human amino acid repeats with similar sequences located in non-coding regions and thus evolving with no selective constraints. It has been estimated that around 90% of the amino acid repeats conserved in other mammalian species are likely to have been shaped by selection. Many of these sequences are likely to participate in transcriptional regulation, including several repeats that are known to cause disease when expanded.
Reference work: Mularoni L, Ledda A, Toll-Riera M, Albà MM. Natural selection drives the accumulation of amino acid tandem repeats in human proteins. Genome Research, published in advance 24th march 2010. http://genome.cshlp.org/content/early/2010/03/23/gr.101261.109.abstract)