AMINO-ACID SUBSTITUTIONS IN THE STRUCTURED DOMAINS OF HISTONES H3 ANDH4 PARTIALLY RELIEVE THE REQUIREMENT OF THE YEAST SWI SNF COMPLEX FORTRANSCRIPTION/
W. Kruger et al., AMINO-ACID SUBSTITUTIONS IN THE STRUCTURED DOMAINS OF HISTONES H3 ANDH4 PARTIALLY RELIEVE THE REQUIREMENT OF THE YEAST SWI SNF COMPLEX FORTRANSCRIPTION/, Genes & development, 9(22), 1995, pp. 2770-2779
Transcription of many yeast genes requires the SWI/SNF regulatory comp
lex. Prior studies show that reduced transcription of the HO gene in s
wi and snf mutants is partially relieved by mutations in the SIN1 and
SIN2 genes. Here we show that SIN2 is identical to HHT1, one of the tw
o genes coding for histone H3, and that mutations in either can result
in a Sin(-) phenotype. These mutations are partially dominant to wild
type and cause amino acid substitutions in three conserved positions
in the structured domain of histone H3. We have also identified partia
lly dominant sin mutations that affect two conserved positions in the
histone-fold domain of histone H4. Three sin mutations affect surface
residues proposed to interact with DNA and may reduce affinity of DNA
for the histone octamer. Two sin mutations affect residues at or near
interfaces between (H2A-H2B) dimer and (H3-H4)(2) tetramer subunits of
the histone octamer and may affect nucleosome stability or conformati
on. The ability of mutations affecting the structure of the histone oc
tamer to relieve the need for SWI and SNF products supports the propos
al that the SWI/SNF complex stimulates transcription by altering chrom
atin structure and can account for the apparent conservation of SWI an
d SNF proteins in eukaryotes other than yeast.