FIG. 6.

Changes in the chromatin structure of SNR6 under active or repressed conditions. For clarity, Pol III transcription machinery, which remains on the gene even under repression, is omitted. The bar denotes the DNA region exposed under these conditions. The position of the nucleosome between the A and B boxes (dark gray oval) does not change while the upstream nucleosome (shown in light gray) moves. When the gene is activated, RSC, SWR1, and SAS complexes are recruited to the gene. RSC slides one nucleosome to a position upstream of the TATA box, and H2A in this nucleosome is exchanged with H2A.Z by the SWR1 complex. The SAS complex acetylates H4K16. When the gene is repressed, RSC, SAS, and H2A.Z are lost, and this nucleosome goes back to cover the TATA box and transcription start site.