Spt16-Pob3 and the HMG protein Nhp6 combine to form the nucleosome-binding factor SPN

• Published in: The EMBO journal Vol. 20; no. 13; pp. 3506 - 3517
• Main Authors: Formosa, Tim, Eriksson, Peter, Wittmeyer, Jacqui, Ginn, Jennifer, Yu, Yaxin, Stillman, David J.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 02.07.2001; Blackwell Publishing Ltd; Oxford University Press
• Subjects: AHO gene; Alleles; Amino Acid Substitution; Antigens, Nuclear; Carrier Proteins - genetics; Carrier Proteins - metabolism; cdc68; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Deoxyribonucleic acid; DNA; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Fungal Proteins - genetics; Fungal Proteins - metabolism; Gene Expression Regulation, Fungal; Genotype; High Mobility Group Proteins - genetics; High Mobility Group Proteins - metabolism; Histones - metabolism; HMGN Proteins; HO gene; Humans; Mutagenesis, Site-Directed; Nhp6; Nhp6 protein; NHP6A gene; NHP6B gene; Nuclear Matrix-Associated Proteins; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; nucleosome; Nucleosomes - genetics; Nucleosomes - physiology; Phenotype; Pob3; POB3 gene; pob3 protein; Protein Subunits; Recombinant Proteins - metabolism; Rpd3 protein; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - physiology; Saccharomyces cerevisiae Proteins; Spindle Apparatus; SPN protein; Spt16; SPT16 gene; Spt16 protein; Transcription Factors; Transcription, Genetic; Transcriptional Elongation Factors; Yeasts
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/20.13.3506

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.