Bell, S. D., Botting, C. H. Wardleworth, B. N., Jackson, S. P. and White, M. F. (2002) Alba, a conserved archaeal chromatin protein, interacts with Sir2 and is regulated by acetylation. Science 296:148-151.    

The conserved Sir2 family of proteins possesses NAD-dependent protein deacetylase activity. While histones are one likely target for the enzymatic activity of eukaryotic Sir2 proteins, little is known about the substrates and roles of prokaryotic Sir2 homologs. We reveal that an archaeal Sir2 homolog interacts specifically with the major archaeal chromatin protein, Alba, and that Alba exists in acetylated and non-acetylated forms. Furthermore, we show that Sir2 can deacetylate Alba and mediate transcriptional repression in a reconstituted in vitro transcription system. These data provide a paradigm for how Sir2 family proteins influence transcription and suggest that modulation of chromatin structure by acetylation arose prior to the divergence of the archaeal and eukaryotic lineages.