Activation domains drive nucleosome eviction by SWI/SNF

Abstract

ATP-dependent chromatin remodeling complexes play a critical role in chromatin dynamics. A large number of in vitro studies have pointed towards nucleosome sliding as the principal remodeling outcome of SWI/SNF action, whereas few have described histone octamer transfer as the principal outcome. In contrast, recent in vivo studies have linked the activity of SWI/SNF to histone eviction in trans from gene promoters. In this study, we have found that the chimeric transcription factor Gal4-VP16 can enhance SWI/SNF histone octamer transfer activity, resulting in targeted histone eviction from a nucleosome probe. This effect is dependent on the presence of the activation domain. We observed that under conditions mimicking the in vivo relative abundance of SWI/SNF with respect to the total number of nucleosomes in a cell nucleus, the accessibility of the transcription factor binding site is the first determinant in the sequence of events leading to nucleosome remodeling. We propose a model mechanism for this transcription factor-mediated enhancement of SWI/SNF octamer transfer activity.

The coactivators CBP/p300 and the histone chaperone NAP1 promote transcription-independent nucleosome eviction at the HTLV-1 promoter

“…These data indicate that the four core histones are the major targets of p300 acetylation and strongly support a role for histone hyperacetylation in NAP1-dependent nucleosome eviction. (19). Time of MNase treatment is indicated.…”

“…We therefore considered whether NAP1 plays a role in nucleosome eviction from the HTLV-1 promoter. To explore this possibility, we assembled chromatin templates in the absence of assembly proteins by salt deposition (19). This method produces chromatin that is indistinguishable from that formed by using the assembly factors, as measured by micrococcal nuclease assays and response to Tax/pCREB activation in an in vitro transcription assay (Figs.…”

“…For salt deposition, the immobilized template DNA and histones were mixed together in a reaction containing 1 M NaCl, 10 mM Tris⅐HCl (pH 8.0), and 1 mM EDTA. Nucleosome deposition was performed as described (19) by stepwise dilution of the NaCl in the sample with 10 mM Tris⅐HCl (pH 8.0) containing 1 mM EDTA to a final NaCl concentration of 0.1 M. Each dilution step was incubated for 45 min at 4°C with shaking. The assembled chromatin was stored in a buffer containing 0.1 M NaCl, 0.1% Nonidet P-40, 10 mM Tris-HCl (pH 7.5), 1 mM EDTA, 5 mM DTT, and 20% glycerol at 4°C.…”

Poly(ADP-ribosyl)ation directs recruitment and activation of an ATP-dependent chromatin remodeler

“…Mononucleosomes were reconstituted by dilution transfer from HeLa oligonucleosomes on a 32 P-end-labeled 216-bp DNA fragment (601-lat Gal4) generated by PCR from pGEM3Z-601-Gal4 (37,38). F-Alc1 (1 pmol) from HEK293/FRT or SF9 cells was incubated at 32°C for 30 min with mononucleosomes (Ϸ0.01 pmol labeled mononucleosome, Ϸ0.25 pmol unlabeled oligonucleosomes) in 20 mM HEPES-NaOH, pH 7.9, 50 mM NaCl, 4.5 mM MgCl2, 2 mM DTT, 0.5 mM PMSF, 45 g/mL BSA, 10% glycerol, 0.02% Triton X-100, 0.02% Nonidet P-40, and 2 mM ATP.…”

Nucleosome Remodeling and Epigenetics

“…Nucleosome displacement by Swi/Snf is facilitated by histone acetylation (see Fig. 9, and Section 7) and by interactions of the complexes with transcription factors (Gutierrez et al 2007). …”