Spt16-Pob3 and the HMG protein Nhp6 combine to form the nucleosome-binding factor SPN.
Yeast Spt16/Cdc68 and Pob3 form a heterodimer that acts in both DNA replication and transcription. This is supported by studies of new alleles of SPT16 described here. We show that Spt16-Pob3 enhances HO transcription through a mechanism that is affected by chromatin modification, since some of the defects caused by mutations can be suppressed by deleting the histone deacetylase Rpd3. While otherwise conserved among many eukaryotes, Pob3 lacks the HMG1 DNA-binding motif found in similar proteins such as the SSRP1 subunit of human FACT. SPT16 and POB3 display strong genetic interactions with NHP6A/B, which encodes an HMG1 motif, suggesting that these gene products function coordinately in vivo. While Spt16-Pob3 and Nhp6 do not appear to form stable heterotrimers, Nhp6 binds to nucleosomes and these Nhp6-nucleosomes can recruit Spt16-Pob3 to form SPN-nucleosomes. These complexes have altered electrophoretic mobility and a distinct pattern of enhanced sensitivity to DNase I. These results suggest that Spt16-Pob3 and Nhp6 cooperate to function as a novel nucleosome reorganizing factor.
Formosa
T
T
Department of Biochemistry, University of Utah School of Medicine, 50 N. Medical Drive Rm 211, Salt Lake City, UT 84132, USA. Tim.Formosa@hsc.utah.edu
Eriksson
P
P
Wittmeyer
J
J
Ginn
J
J
Yu
Y
Y
Stillman
D J
DJ
D000483:Alleles; D019943:Amino Acid Substitution; D034961:Antigens, Nuclear; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005838:Genotype; D024001:HMGN Proteins; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D016297:Mutagenesis, Site-Directed; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009707:Nucleosomes / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus; D014157:Transcription Factors; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors
D034961:Antigens, Nuclear; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D024001:HMGN Proteins; D006609:High Mobility Group Proteins; D006657:Histones; C086471:NHP6A protein, S cerevisiae; C086472:NHP6B protein, S cerevisiae; C050045:NUMA1 protein, human; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D009707:Nucleosomes; C106768:POB3 protein, S cerevisiae; D021122:Protein Subunits; D011994:Recombinant Proteins; C071238:SPT16 protein, S cerevisiae; C073537:SSRP1 protein, human; C489489:SUPT16H protein, human; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors