spt16 (S. pombe) - Research Notes
Gene Identity
- UniProt: O94267
- PomBase: SPBP8B7.19
- Essential gene in S. pombe PMID:17614284
- 1019 AA, chromosome II
FACT Complex Composition in S. pombe
- Spt16 (large subunit, essential) + Pob3 (small subunit, non-essential) form the core heterodimer PMID:17614284
- In S. pombe, pob3 deletion is viable (unlike S. cerevisiae where both subunits are essential) PMID:17614284
- nhp6 associates weakly to form the complete FACT complex (by similarity to other organisms)
Structural Biology
- Crystal structures of N-terminal "peptidase" domain at 2.05A and 1.84A (PDB: 3CB5, 3CB6) PMID:18579787
- N-terminal domain has aminopeptidase P fold but lacks enzymatic activity - repurposed for histone binding PMID:18579787
- Spt16-N binds H3-H4 through globular core domains and N-terminal tails PMID:18579787
- Spt16-M domain required for interaction with Pob3 PMID:17614284
- C-terminal acidic tail (residues 930-1019) characteristic of histone chaperones
Core Functions
1. Histone Chaperone Activity
- H2A-H2B chaperone activity: directly demonstrated [PMID:31837996 EXP with contributes_to qualifier; PMID:34731638 EXP]
- H3-H4 binding via N-terminal domain PMID:18579787
- General histone chaperone activity [PMID:23028377 IMP]
- Maintains H3 chromatin integrity during transcription - prevents promiscuous CENP-A(Cnp1) deposition PMID:23028377
2. Transcription Elongation
- Facilitates RNA Pol II passage through chromatin by transiently destabilizing nucleosomes PMID:28218250
- Cooperates with Fun30/Fft3 chromatin remodeler for nucleosome disassembly at transcribing regions PMID:28218250
- Globally represses antisense transcripts near 5' end of genes PMID:31837996
- In absence of Pob3, Spt16 alone controls 3' end of genes PMID:31837996
3. Heterochromatin Functions
- Required for centromeric heterochromatin integrity, independently of RNAi PMID:17614284
- Facilitates heterochromatin spreading by regulating histone turnover and H3K9 methylation states PMID:34731638
- Constitutive heterochromatin formation role demonstrated by IMP PMID:34731638
- Concentrates on euchromatin but affects heterochromatin boundaries PMID:34731638
4. Chromatin Organization and Genome Architecture
- Maintains nucleosomes in subtelomeric regions, crucial for their compaction PMID:31837996
- H2Bub is required for FACT activity in genic regions PMID:31837996
- Chromatin remodeling demonstrated by IMP PMID:31837996
5. DNA Replication-coupled Functions
- FACT regulates parental histone transfer to both DNA strands during replication PMID:38479839
- Collaborates with Mcm2 and Dpb3/4 for epigenetic inheritance PMID:38479839
Localization
Protein Interactions
Reference Verification
All PMIDs cited in existing GOA annotations verified as real:
- PMID:16823372 - ORFeome localization study (2006, Nat Biotechnol) - REAL
- PMID:17614284 - FACT contributes to centromeric heterochromatin (2007, Curr Biol) - REAL
- PMID:18579787 - Spt16 peptidase domain binds H3-H4 (2008, PNAS) - REAL
- PMID:23028377 - FACT prevents promiscuous CENP-A deposition (2012, PLoS Genet) - REAL
- PMID:31837996 - FACT and H2Bub maintain genome architecture (2020, Mol Cell) - REAL
- PMID:34731638 - FACT facilitates heterochromatin spreading (2021, Cell Rep) - REAL
- PMID:38479839 - Histone chaperone coordination during replication (2024, Genes Dev) - REAL
PMID:28218250 cited in UniProt (not in GOA):
- Lee et al. 2017, Nat Commun - Fun30/Fft3 and FACT cooperation - REAL
ProtNLM pre-release paragraph assessment
The exact source paragraph and eleven atomic claims are recorded in spt16-protnlm-function-review.md. Established complex membership, transcription/replication roles and chromatin reassembly are supported. The asserted dissociation of exactly one H2A-H2B dimer is not required by the mechanistic literature: PMID:19683499. The main biological description therefore describes nucleosome reorganization without making dimer eviction obligatory.