POB3/YML069W Summary Help

Standard Name POB3 1
Systematic Name YML069W
Feature Type ORF, Verified
Description Subunit of the heterodimeric FACT complex (Spt16p-Pob3p); FACT associates with chromatin via interaction with Nhp6Ap and Nhp6Bp, and reorganizes nucleosomes to facilitate access to DNA by RNA and DNA polymerases; protein abundance increases in response to DNA replication stress (1, 2, 3, 4, 5, 6, 7 and see Summary Paragraph)
Name Description POl1 Binding 1
Chromosomal Location
ChrXIII:135500 to 137158 | ORF Map | GBrowse
Gene Ontology Annotations All POB3 GO evidence and references
  View Computational GO annotations for POB3
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 2 genes
Classical genetics
Large-scale survey
reduction of function
340 total interaction(s) for 190 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 117
  • Affinity Capture-RNA: 5
  • Affinity Capture-Western: 31
  • Co-fractionation: 2
  • Reconstituted Complex: 4

Genetic Interactions
  • Dosage Growth Defect: 5
  • Dosage Lethality: 2
  • Dosage Rescue: 5
  • Negative Genetic: 101
  • Phenotypic Enhancement: 2
  • Positive Genetic: 16
  • Synthetic Growth Defect: 18
  • Synthetic Lethality: 19
  • Synthetic Rescue: 13

Expression Summary
Length (a.a.) 552
Molecular Weight (Da) 62,993
Isoelectric Point (pI) 4.57
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXIII:135500 to 137158 | ORF Map | GBrowse
Last Update Coordinates: 1996-07-31 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1659 135500..137158 1996-07-31 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000004534

The FACT ("FAcilitates Chromatin Transcription" or "FAcilitates Chromatin Transactions") complex is a heterodimer consisting of Pob3p and Spt16p (4, reviewed in 8). Both subunits of the FACT complex are highly conserved, but in higher eukaryotes the Pob3p homolog contains an HMGB DNA binding motif that mediates chromatin binding (reviewed in 9), while in S. cerevisiae, chromatin association of the complex is mediated by the small HMG-box protein Nhp6 (encoded by two nearly identical genes, NHP6A and NHP6B) (4). Although Pob3p, Spt16p, and Nhp6Ap/Nhp6Bp do not form a stable heterotrimer, the Nhp6 protein is necessary for activity of the FACT complex (4, 6).

The FACT complex interacts with nucleosomes in multiple ways, primarily via the DNA binding activity of Nhp6p (reviewed in 10), but additionally Pob3p and Spt16p both display histone binding activity (11). The complex is able to alter chromatin structure without the requirement for ATP hydrolysis, in a mechanism distinct from ATP-dependent chromatin remodeling (12, 6). The alterations in chromatin have often been referred to as disassembly and reassembly, but recent work suggests that the process may involve a conformational change between tighter and looser nucleosomal structures rather than disintegration of the nucleosome, and is more accurately called nucleosome reorganization (6). FACT has been implicated in several processes that require the access of large enzyme complexes to DNA: transcription initiation, transcription elongation, and DNA replication (reviewed in 8). In RNA polymerase II (RNAP II) transcription initiation, the FACT complex increases chromatin accessibility to transcription factors within promoter regions (13, 5). However, it does not seem to have a role in chromatin reassembly within promoters after transcription initiation (13). This is in contrast to its role in transcription elongation, where it is thought to reorganize nucleosomes before the passage of RNAP II, and also to restore them to their original state afterwards (14, 15, 16). The role of FACT in DNA replication has been less studied in yeast than in other organisms (reviewed in 9), but there is both genetic and physical evidence for the involvement of the FACT complex in DNA replication in S. cerevisiae (17, 1, 18).

Last updated: 2010-03-05 Contact SGD

References cited on this page View Complete Literature Guide for POB3
1) Wittmeyer J and Formosa T  (1997) The Saccharomyces cerevisiae DNA polymerase alpha catalytic subunit interacts with Cdc68/Spt16 and with Pob3, a protein similar to an HMG1-like protein. Mol Cell Biol 17(7):4178-90
2) Evans DR, et al.  (1998) The yeast protein complex containing cdc68 and pob3 mediates core-promoter repression through the cdc68 N-terminal domain. Genetics 150(4):1393-405
3) Brewster NK, et al.  (1998) Characterization of the CP complex, an abundant dimer of Cdc68 and Pob3 proteins that regulates yeast transcriptional activation and chromatin repression. J Biol Chem 273(34):21972-9
4) Formosa T, et al.  (2001) Spt16-Pob3 and the HMG protein Nhp6 combine to form the nucleosome-binding factor SPN. EMBO J 20(13):3506-17
5) Biswas D, et al.  (2005) The yeast FACT complex has a role in transcriptional initiation. Mol Cell Biol 25(14):5812-22
6) Xin H, et al.  (2009) yFACT induces global accessibility of nucleosomal DNA without H2A-H2B displacement. Mol Cell 35(3):365-76
7) Tkach JM, et al.  (2012) Dissecting DNA damage response pathways by analysing protein localization and abundance changes during DNA replication stress. Nat Cell Biol 14(9):966-76
8) Formosa T  (2008) FACT and the reorganized nucleosome. Mol Biosyst 4(11):1085-93
9) Belotserkovskaya R and Reinberg D  (2004) Facts about FACT and transcript elongation through chromatin. Curr Opin Genet Dev 14(2):139-46
10) Stillman DJ  (2010) Nhp6: A small but powerful effector of chromatin structure in Saccharomyces cerevisiae. Biochim Biophys Acta 1799(1-2):175-180
11) Vandemark AP, et al.  (2008) Structural and Functional Analysis of the Spt16p N-terminal Domain Reveals Overlapping Roles of yFACT Subunits. J Biol Chem 283(8):5058-68
12) Rhoades AR, et al.  (2004) Structural features of nucleosomes reorganized by yeast FACT and its HMG box component, Nhp6. Mol Cell Biol 24(9):3907-17
13) Ransom M, et al.  (2009) FACT and the Proteasome Promote Promoter Chromatin Disassembly and Transcriptional Initiation. J Biol Chem 284(35):23461-71
14) Belotserkovskaya R, et al.  (2003) FACT facilitates transcription-dependent nucleosome alteration. Science 301(5636):1090-3
15) Formosa T, et al.  (2002) Defects in SPT16 or POB3 (yFACT) in Saccharomyces cerevisiae cause dependence on the Hir/Hpc pathway: polymerase passage may degrade chromatin structure. Genetics 162(4):1557-71
16) Jamai A, et al.  (2009) Histone chaperone spt16 promotes redeposition of the original h3-h4 histones evicted by elongating RNA polymerase. Mol Cell 35(3):377-83
17) Schlesinger MB and Formosa T  (2000) POB3 is required for both transcription and replication in the yeast Saccharomyces cerevisiae. Genetics 155(4):1593-606
18) Vandemark AP, et al.  (2006) The structure of the yFACT Pob3-M domain, its interaction with the DNA replication factor RPA, and a potential role in nucleosome deposition. Mol Cell 22(3):363-74