The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The identity check is positive: the requested cbh1 encodes CENP-B homolog protein 1 (Cbh1/CBHP-1) in Schizosaccharomyces pombe, and the literature consistently places it with the paralogs Abp1 and Cbh2 in the fission-yeast CENP-B family. This is not an unrelated fungal cbh1 cellobiohydrolase gene. Nevertheless, literature specific to Cbh1 is sparse; many detailed biochemical findings concern Abp1 or all three paralogs collectively and cannot safely be assigned to Cbh1 alone. (johansen2015suppressionofmeiotic pages 1-2, lorenz2012cenpbcooperateswith pages 2-3)
The best-supported primary function is that Cbh1 is a nuclear, chromatin-associated DNA-binding protein that helps recognize and control repetitive DNA, especially Tf2 retrotransposons and their long terminal repeats (LTRs). It contributes redundantly to transcriptional repression and higher-order organization of these elements and modestly suppresses meiotic homologous recombination at Tf2 loci. It should not presently be annotated as an active nuclease or transposase: although its DDE-superfamily and CENP-B-like domains reflect descent from a pogo-like transposase, no Cbh1-specific catalytic reaction or substrate-cleavage assay was identified. (lorenz2012cenpbcooperateswith pages 2-3, mateo2014pogoliketransposaseshave pages 1-2)
| Annotation question | Best-supported conclusion | Evidence type / strength | Key caveat |
|---|---|---|---|
| Identity | Cbh1/CBHP-1 (UniProt O14423) is an S. pombe CENP-B homolog, distinct from unrelated fungal cbh1 cellobiohydrolases. | Direct literature identification; high (johansen2015suppressionofmeiotic pages 1-2) | Cbh1 is one of three paralogs—Abp1, Cbh1, and Cbh2—so family-level findings are not automatically Cbh1-specific. |
| Primary molecular role | A chromatin-associated, sequence-selective DNA-binding CENP-B-family protein involved in repetitive-DNA control and genome organization—not a demonstrated enzyme. | Localization plus genetics; moderate (lorenz2012cenpbcooperateswith pages 2-3) | No purified-Cbh1 biochemical assay has established nuclease/transposase catalysis or a reaction/substrate pair. |
| Direct genomic localization | Cbh1 and Abp1 occupy all full-length Tf2 retrotransposons and most solo LTRs. | Chromatin-occupancy evidence; high (lorenz2012cenpbcooperateswith pages 2-3) | The cited result reports shared Abp1/Cbh1 occupancy; a Cbh1-specific binding motif was not defined. |
| Genetic redundancy | Cbh1 acts redundantly with Abp1/Cbh2: abp1Δ cbh1Δ aggravates Tf2 derepression and slow growth, while combined Abp1–Cbh1 loss can cause inviability and severe branching/elongation. | Mutant genetics; moderate–high (lorenz2012cenpbcooperateswith pages 2-3, locovei2006thecenpbhomolog pages 1-2) | Abp1 usually has the dominant phenotype; Cbh1 deletion alone often has weak or undetectable effects. |
| Meiotic recombination at Tf2-12 | cbh1Δ: 2.13% versus wild type: 0.96%—approximately 2.2-fold higher. | Locus-specific recombination assay; moderate (johansen2015suppressionofmeiotic pages 8-14) | The excerpt supplies no Cbh1-specific mechanistic test or statistical significance value. |
| Meiotic recombination at tandem Tf2-7/8 | cbh1Δ: 1.85% versus wild type: 1.24%—approximately 1.5-fold higher. | Locus-specific recombination assay; moderate (johansen2015suppressionofmeiotic pages 8-14) | The effect is modest and substantially weaker than the Abp1-loss phenotype. |
| Pericentromeric heterochromatin | Cbh1 likely contributes with Abp1/Cbh2 to pericentromeric heterochromatin assembly and Swi6/HP1 recruitment. | Family-level evidence; low–moderate for Cbh1 individually (marina2012understandingtheroles pages 15-20) | Direct, Cbh1-only recruitment or loss-of-function evidence is limited; do not treat Cbh1 as a core kinetochore enzyme. |
| Evolution and domains | Cbh1 is inferred to be a domesticated pogo-like transposase, consistent with CENP-B/HTH DNA-binding and DDE-superfamily annotations. | Comparative evolution plus domain inference; high for origin, moderate for function (lorenz2012cenpbcooperateswith pages 4-5, mateo2014pogoliketransposaseshave pages 1-2) | Domain homology does not prove that Cbh1 retains catalytic DDE endonuclease activity or the exact architecture experimentally established for Abp1. |
| 2023–2024 evidence | No direct 2023–2024 functional study of S. pombe Cbh1 was identified; a May 2023 comparative study reported no identifiable homologs of the S. pombe CENP-B-like genes in other surveyed fungi. | Literature search plus comparative genomics; moderate (cisse2023thehostadapted pages 5-9) | The 2023 result concerns evolutionary distribution, not direct Cbh1 function, and was reported as a bioRxiv preprint. |
Table: Evidence-grading summary for functional annotation of Schizosaccharomyces pombe Cbh1, separating direct Cbh1 findings from paralog-family evidence and domain-based inference.
The supplied UniProt identity—O14423; CENP-B homolog protein 1; gene cbh1/cbh; ORF SPAC9E9.10c; S. pombe strain 972—is aligned with the literature. Cbh1 is repeatedly identified as one of three S. pombe CENP-B homologs, alongside Abp1 and Cbh2. (johansen2015suppressionofmeiotic pages 2-3, johansen2015suppressionofmeiotic pages 1-2)
The symbol is genuinely ambiguous outside this organism. In several filamentous fungi, cbh1 commonly denotes a secreted cellobiohydrolase/cellulase. Those proteins are unrelated to O14423 and were excluded. Accordingly, all conclusions below apply specifically to S. pombe Cbh1/CBHP-1.
The user-supplied InterPro assignments—CenT-element-derived, DDE-superfamily endonuclease, homeodomain-like, HTH_ABP1_N, and HTH CENP-B DNA-binding—fit the established evolutionary model in which fission-yeast CENP-B proteins arose by domestication of a pogo-like DNA transposase. Comparative analyses regard the mammalian and fission-yeast CENP-B systems as independent transposase-domestication events rather than simple one-to-one orthology. (johansen2015suppressionofmeiotic pages 6-7, mateo2014pogoliketransposaseshave pages 1-2)
The family architecture is described as an N-terminal DNA-binding region, a central transposase-derived region containing a DDE-like motif, and a C-terminal dimerization region. However, the strongest experimental dissection of these modules was performed on Abp1, not Cbh1. Abp1’s N-terminal domain is required for LTR binding, whereas deletion of its DDE-like or dimerization regions has weaker effects on occupancy. These observations make the corresponding Cbh1 domains biologically plausible but do not demonstrate identical biochemical behavior. (lorenz2012cenpbcooperateswith pages 4-5)
No purified-Cbh1 study establishing DNA cleavage, strand transfer, transposition, or another catalytic reaction was found. Therefore:
The DDE annotation is thus evidence of evolutionary origin and possible retained structural function, not sufficient proof of active endonuclease chemistry.
The clearest localization evidence is that Cbh1 and Abp1 occupy all full-length Tf2 retrotransposons and most solo LTRs. This places Cbh1 physically at its most defensible functional substrate: chromosomal retrotransposon-associated DNA. A Cbh1-specific recognition sequence has not been defined in the retrieved evidence. The TA-rich LTR motif and detailed DNA-binding measurements often discussed in this context were mapped for Abp1 and should not automatically be transferred to Cbh1. (lorenz2012cenpbcooperateswith pages 2-3, lorenz2012cenpbcooperateswith pages 4-5)
Cbh1 appears to support Tf2 silencing redundantly. Loss of Abp1 causes strong Tf2 upregulation, and additional deletion of cbh1 enhances that phenotype. This argues that Cbh1 contributes to repression but is normally masked by the stronger Abp1 pathway. (lorenz2012cenpbcooperateswith pages 2-3)
The redundancy is assay-dependent. In a 2016 analysis of 50–200-nt transcripts from repetitive DNA, cbh1Δ alone did not reproduce the abp1Δ phenotype, and abp1Δ cbh1Δ showed no synergistic increase. Thus Cbh1 has little detectable role in that particular short-RNA/pervasive-transcription readout, despite contributing in other Tf2-expression assays. (daulny2016thefissionyeast pages 3-5)
Fission-yeast CENP-B proteins organize dispersed Tf2 elements into subnuclear Tf bodies. Mechanistic studies centered on Abp1 indicate a pathway in which Abp1 recruits Ku, Ku recruits condensin, and condensin promotes clustering of Tf elements with centromeres. Tf clustering and centromere association are significantly impaired in Ku or condensin mutants, including a reported p < 0.00001 for the cut14-208 condensin defect. These findings establish the broader pathway but do not prove that Cbh1 itself recruits Ku or condensin. (tanaka2012epigeneticregulationof pages 4-5, tanaka2012epigeneticregulationof pages 3-4)
The conservative Cbh1 annotation is therefore “contributes redundantly to Tf-body formation/genome organization,” not “direct condensin recruiter.” Family-level evidence also connects CENP-B proteins with histone deacetylases and Set1 in Tf2 repression and organization. (johansen2015suppressionofmeiotic pages 2-3, johansen2015suppressionofmeiotic pages 1-2)
The strongest Cbh1-specific quantitative phenotype is increased meiotic recombination near Tf2 elements after cbh1 deletion:
For comparison, Abp1 deletion generated substantially stronger effects in the same study, approximately fivefold at Tf2-12 and 3.5-fold at Tf2-7/8. Cbh1 is therefore best interpreted as an auxiliary suppressor of recombination, not the dominant family member. The cbh1Δ cbh2Δ combinations were not consistently more severe than the single deletions, illustrating non-additive redundancy and the complexity of this paralog system. (johansen2015suppressionofmeiotic pages 2-3, johansen2015suppressionofmeiotic pages 8-14)
Recombination suppression is biologically coherent because ectopic homologous recombination among repeated elements can generate deletions, duplications, and inversions. CENP-B-family proteins, Ku, Set1, and condensin provide overlapping layers of protection at Tf2 loci. (johansen2015suppressionofmeiotic pages 5-6, johansen2015suppressionofmeiotic pages 6-7)
Cbh1, Abp1, and Cbh2 are described collectively as pericentromeric DNA-binding proteins that contribute to heterochromatin assembly and recruitment of Swi6, the S. pombe HP1 homolog. Proposed recruitment of histone deacetylases and histone methyltransferases provides a plausible chromatin-silencing mechanism, but the precise mechanism and the individual contribution of Cbh1 remain incompletely resolved. (marina2012understandingtheroles pages 15-20, marina2012understandingtherolesa pages 15-20)
This distinction matters: Cbh1 is associated with pericentromeric heterochromatin, but it should not be equated with the core kinetochore determinant CENP-A/Cnp1, nor should family-wide Swi6 recruitment be presented as a Cbh1-only biochemical interaction.
Cbh1 is individually nonessential under standard conditions, but abp1Δ cbh1Δ was reported to cause loss of viability and severe branching and elongation. This synthetic phenotype indicates that Abp1 and Cbh1 perform overlapping functions required for normal cell-cycle progression or chromosome maintenance. (locovei2006thecenpbhomolog pages 1-2)
Abp1 itself interacts genetically and physically with DNA-replication initiation machinery, but no equivalent direct interaction was established for Cbh1 in the retrieved studies. Consequently, “DNA replication” is best treated as a family-associated or redundancy-supported process, not a demonstrated direct Cbh1 mechanism.
Cbh1 acts inside the nucleus on chromatin. Its most directly supported sites are full-length Tf2 elements and most solo LTRs. Family-level evidence also places CENP-B homologs at pericentromeric repeats. Tf2 elements are organized into nuclear Tf bodies that frequently associate with centromeres and the nuclear periphery, but direct imaging of a Cbh1-specific protein focus was not identified. (lorenz2012cenpbcooperateswith pages 2-3, tanaka2012epigeneticregulationof pages 4-5)
Accordingly, a suitable localization annotation is:
Nucleus; chromosome/chromatin; enriched at Tf2 retrotransposons, solo LTRs, and probably pericentromeric repetitive chromatin.
There is no evidence that Cbh1 is secreted, membrane-associated, or acts outside the cell.
The accepted evolutionary interpretation is transposase domestication: an ancestral pogo-like mobile-element protein was co-opted as a host chromatin regulator. Cbh1 therefore exemplifies molecular exaptation, in which a transposon-derived DNA-recognition architecture was repurposed to restrain repetitive elements and stabilize chromosomes. (johansen2015suppressionofmeiotic pages 6-7, mateo2014pogoliketransposaseshave pages 1-2)
No direct 2023–2024 functional study centered on S. pombe Cbh1 was identified. The most relevant recent source is a May 2023 bioRxiv comparative study of Pneumocystis centromeres. It reported no identifiable homologs of the S. pombe CENP-B-like genes in other surveyed fungi, supporting the view that this transposase-derived system is lineage-specific rather than a universally conserved fungal centromere module. This is comparative evolutionary evidence, not a Cbh1 functional experiment. URL: https://doi.org/10.1101/2023.05.12.540427. (cisse2023thehostadapted pages 5-9)
The lack of recent direct studies is itself important for annotation: current understanding still rests principally on studies from 2006–2016, and Cbh1 remains substantially less characterized than Abp1.
Cbh1 has no known clinical, industrial, or biotechnological implementation. Its present application is as a research-system component for studying:
The S. pombe system is particularly useful because cbh1 deletion yields measurable but relatively mild phenotypes, while combinations with abp1 expose genetic redundancy. This enables separation of primary and backup genome-surveillance pathways.
Primary molecular function: CENP-B-family chromatin DNA-binding protein that associates with Tf2 retrotransposons/LTRs and contributes redundantly to their transcriptional repression and nuclear organization.
Primary biological role: maintenance of repetitive-DNA stability, including modest suppression of meiotic homologous recombination at Tf2 elements.
Secondary/family-supported roles: contribution to pericentromeric heterochromatin/Swi6 recruitment, Tf-body formation, chromosome organization, and cell-cycle robustness.
Localization: nuclear chromatin; full-length Tf2 elements, most solo LTRs, and family-level association with pericentromeric repeats.
Catalytic status: no demonstrated enzymatic activity. The DDE-superfamily annotation should be recorded as transposase-derived domain homology rather than evidence that Cbh1 is an active endonuclease.
The central interpretive hazard is paralog conflation. Abp1 is the dominant and most experimentally characterized S. pombe CENP-B protein. Its LTR motif recognition, Ku/condensin recruitment, replication interactions, and pervasive-transcription phenotypes should not be assigned directly to Cbh1 without dedicated experiments. The strongest Cbh1-specific evidence consists of genomic co-occupancy with Abp1, enhancement of abp1 mutant phenotypes, synthetic loss of viability with abp1, and modest elevation of Tf2-associated meiotic recombination. (johansen2015suppressionofmeiotic pages 8-14, lorenz2012cenpbcooperateswith pages 2-3, daulny2016thefissionyeast pages 3-5, locovei2006thecenpbhomolog pages 1-2)
References
(johansen2015suppressionofmeiotic pages 1-2): Peter Johansen and Hugh P Cam. Suppression of meiotic recombination by cenp-b homologs in schizosaccharomyces pombe. Genetics, 201:897-904, Sep 2015. URL: https://doi.org/10.1534/genetics.115.179465, doi:10.1534/genetics.115.179465. This article has 12 citations and is from a domain leading peer-reviewed journal.
(lorenz2012cenpbcooperateswith pages 2-3): David R. Lorenz, Irina V. Mikheyeva, Peter Johansen, Lauren Meyer, Anastasia Berg, Shiv I. S. Grewal, and Hugh P. Cam. Cenp-b cooperates with set1 in bidirectional transcriptional silencing and genome organization of retrotransposons. Oct 2012. URL: https://doi.org/10.1128/mcb.00395-12, doi:10.1128/mcb.00395-12. This article has 68 citations and is from a domain leading peer-reviewed journal.
(mateo2014pogoliketransposaseshave pages 1-2): Lidia Mateo and Josefa González. Pogo-like transposases have been repeatedly domesticated into cenp-b-related proteins. Genome Biology and Evolution, 6:2008-2016, Jul 2014. URL: https://doi.org/10.1093/gbe/evu153, doi:10.1093/gbe/evu153. This article has 56 citations and is from a domain leading peer-reviewed journal.
(locovei2006thecenpbhomolog pages 1-2): Alexandra M Locovei, Maria-Grazia Spiga, Katsunori Tanaka, Yota Murakami, and Gennaro D'Urso. The cenp-b homolog, abp1, interacts with the initiation protein cdc23 (mcm10) and is required for efficient dna replication in fission yeast. Cell Division, 1:27-27, Nov 2006. URL: https://doi.org/10.1186/1747-1028-1-27, doi:10.1186/1747-1028-1-27. This article has 19 citations and is from a peer-reviewed journal.
(johansen2015suppressionofmeiotic pages 8-14): Peter Johansen and Hugh P Cam. Suppression of meiotic recombination by cenp-b homologs in schizosaccharomyces pombe. Genetics, 201:897-904, Sep 2015. URL: https://doi.org/10.1534/genetics.115.179465, doi:10.1534/genetics.115.179465. This article has 12 citations and is from a domain leading peer-reviewed journal.
(marina2012understandingtheroles pages 15-20): DB Marina. Understanding the roles of non-coding sequences in heterochromatin assembly in fission. Unknown journal, 2012.
(lorenz2012cenpbcooperateswith pages 4-5): David R. Lorenz, Irina V. Mikheyeva, Peter Johansen, Lauren Meyer, Anastasia Berg, Shiv I. S. Grewal, and Hugh P. Cam. Cenp-b cooperates with set1 in bidirectional transcriptional silencing and genome organization of retrotransposons. Oct 2012. URL: https://doi.org/10.1128/mcb.00395-12, doi:10.1128/mcb.00395-12. This article has 68 citations and is from a domain leading peer-reviewed journal.
(cisse2023thehostadapted pages 5-9): Ousmane H. Cissé, Shelly Curran, H. Diego Folco, Yueqin Liu, Lisa Bishop, Honghui Wang, Elizabeth R. Fischer, A Sally Davis, Spenser Babb-Biernacki, Vinson P. Doyle, Jonathan K. Richards, Sergio A. Hassan, John P. Dekker, Pavel P. Khil, Jason M. Brenchley, Shiv Grewal, Melanie Cushion, Liang Ma, and Joseph A. Kovacs. The host adapted fungal pathogens of pneumocystis genus utilize genic regional centromeres. bioRxiv, May 2023. URL: https://doi.org/10.1101/2023.05.12.540427, doi:10.1101/2023.05.12.540427. This article has 0 citations.
(johansen2015suppressionofmeiotic pages 2-3): Peter Johansen and Hugh P Cam. Suppression of meiotic recombination by cenp-b homologs in schizosaccharomyces pombe. Genetics, 201:897-904, Sep 2015. URL: https://doi.org/10.1534/genetics.115.179465, doi:10.1534/genetics.115.179465. This article has 12 citations and is from a domain leading peer-reviewed journal.
(johansen2015suppressionofmeiotic pages 6-7): Peter Johansen and Hugh P Cam. Suppression of meiotic recombination by cenp-b homologs in schizosaccharomyces pombe. Genetics, 201:897-904, Sep 2015. URL: https://doi.org/10.1534/genetics.115.179465, doi:10.1534/genetics.115.179465. This article has 12 citations and is from a domain leading peer-reviewed journal.
(daulny2016thefissionyeast pages 3-5): Anne Daulny, Eva Mejía-Ramírez, Oscar Reina, Jesus Rosado-Lugo, Lorena Aguilar-Arnal, Herbert Auer, Mikel Zaratiegui, and Fernando Azorin. The fission yeast cenp-b protein abp1 prevents pervasive transcription of repetitive dna elements. Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms, 1859(10):1314-1321, Oct 2016. URL: https://doi.org/10.1016/j.bbagrm.2016.06.009, doi:10.1016/j.bbagrm.2016.06.009. This article has 8 citations and is from a peer-reviewed journal.
(tanaka2012epigeneticregulationof pages 4-5): Atsunari Tanaka, Hideki Tanizawa, Sira Sriswasdi, Osamu Iwasaki, Atreyi G. Chatterjee, David W. Speicher, Henry L. Levin, Eishi Noguchi, and Ken-ichi Noma. Epigenetic regulation of condensin-mediated genome organization during the cell cycle and upon dna damage through histone h3 lysine 56 acetylation. Molecular cell, 48 4:532-46, Nov 2012. URL: https://doi.org/10.1016/j.molcel.2012.09.011, doi:10.1016/j.molcel.2012.09.011. This article has 88 citations and is from a highest quality peer-reviewed journal.
(tanaka2012epigeneticregulationof pages 3-4): Atsunari Tanaka, Hideki Tanizawa, Sira Sriswasdi, Osamu Iwasaki, Atreyi G. Chatterjee, David W. Speicher, Henry L. Levin, Eishi Noguchi, and Ken-ichi Noma. Epigenetic regulation of condensin-mediated genome organization during the cell cycle and upon dna damage through histone h3 lysine 56 acetylation. Molecular cell, 48 4:532-46, Nov 2012. URL: https://doi.org/10.1016/j.molcel.2012.09.011, doi:10.1016/j.molcel.2012.09.011. This article has 88 citations and is from a highest quality peer-reviewed journal.
(johansen2015suppressionofmeiotic pages 5-6): Peter Johansen and Hugh P Cam. Suppression of meiotic recombination by cenp-b homologs in schizosaccharomyces pombe. Genetics, 201:897-904, Sep 2015. URL: https://doi.org/10.1534/genetics.115.179465, doi:10.1534/genetics.115.179465. This article has 12 citations and is from a domain leading peer-reviewed journal.
(marina2012understandingtherolesa pages 15-20): DB Marina. Understanding the roles of non-coding sequences in heterochromatin assembly in fission. Unknown journal, 2012.