Biology Reference
In-Depth Information
TABLE I
S
UBUNIT
C
OMPOSITION OF
RSC
AND
SWI/SNF C
OMPLEXES
S. cerevisiae
Human
RSC
SWI/SNF
hSwi/Snf-B (PBAF)
hSwi/Snf-A (BAF)
Sth1
Snf2
Brg1
Brm or Brg1
b
-Actin
b
-Actin
Arp7
Arp7
Arp9
Arp9
BAF53
BAF53
Rtt102
Rtt102
Rsc6
Swp73
BAF60a
BAF60a
Sfh1
Snf5
Snf5
Snf5
Rsc8
Swi3
BAF170 and BAF155
BAF170 and BAF155
Rsc3
Rsc30
Rsc1 or Rsc2
Polybromo/BAF180
Rsc4
Rsc7
Rsc9
Ldb7
Htl1
Rsc58
BAF57
BAF57
Swi1
BAF250
Snf6
Snf1
Swp29/Tfg3/Anc1/Taf30
Swp82
Catalytic subunits are shown in bold. Yeast RSC and SWI/SNF complexes share Arp7, Arp9, and Rtt102
subunits and four more subunits share homology. The human PBAF complex is homologous to RSC, while BAF
is homologous to SWI/SNF. PBAF and BAF share seven subunits and are defined by the presence of either
BAF180 or BAF250.
subunits of RSC are essential and many contain further chromatin-binding and
regulatory domains (see
Table II
). The lethality that results from deletion of
some RSC subunits demonstrates the importance of RSC function in cells, most
likely in transcription of some essential genes.
Cryo-electron microscopy structural studies on the RSC complex revealed a
large central cavity of sufficient size to accommodate a nucleosome. Incubation
of the complex with nucleosomes led to an increased area of density within the
central cavity, suggesting that this constitutes a nucleosome-binding pocket.
42-44
Images of both the Rsc2-RSC complex isoform
42
and a mixture of Rsc1-
and Rsc2-containing complexes
43,45
showed predominantly two different
conformations, that is, an ''open'' and a ''closed'' conformation that varied
mainly in the position of the lower arm. Incubation with an acetylated H3
N-terminal peptide stabilized the ''closed'' conformation of
this arm.
45
