Chromatin structure and transcriptionSimilar to yeast Sir2, mammalian SIRT1 facilitates the formation of heterochromatin, the more tightly packed form of chromatin associated with histone hypoacetylation and gene repression. SIRT1 targets for deacetylation include lysine residues at positions 9 and 26 of histone H1, 14 of H3, and 16 of H4 (Figure 4) [21,54]. Multiple non-histone targets have also been described (Figure 4). TAFI68 [TBP (TATA-box binding protein)-associated factor I 68], the second largest subunit of the TBP-containing complex, TIF (transcription initiation factor)-IB/SL, which regulates transcription of RNA Pol I (RNA polymerase I), was the first non-histone target described for the mouse SIRT1 protein.
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