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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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 gene tam14 (systematic name SPCC330.20; UniProt accession G2TRT3) encodes a small protein in the fission yeast Schizosaccharomyces pombe (strain 972 / ATCC 24843). It was identified through a systematic reappraisal of the S. pombe genome conducted by Bitton et al. (2011), which used an integrated pipeline combining proteogenomics, comparative genomics, and Pfam domain scanning to discover novel small protein-coding genes that had been missed by previous annotations due to the standard 100-amino-acid cutoff threshold (bitton2011augmentedannotationof pages 1-2). The tam14 locus was specifically identified through a Pfam domain scan that detected a RAMP4-family domain (PF06624) in an intergenic region of the genome (bitton2011augmentedannotationof pages 3-4, bitton2011augmentedannotationof pages 8-10).
The gene was named "tam14" because its transcript levels fluctuate during meiosis—the name stands for "Transcripts Altered in Meiosis protein 14." In the Bitton et al. study, 14 of the 39 newly discovered genes showed altered transcript levels during the sexual differentiation program induced by temperature-dependent inactivation of the Pat1 kinase in pat1.114 diploid cultures, and these were designated tam1–tam14 (bitton2011augmentedannotationof pages 8-10). Transcription at the tam14 locus was confirmed by RT-PCR and RNA-Seq (bitton2011augmentedannotationof pages 1-2). Importantly, tam14 was not among the seven genes selected for functional knockout analysis in the original study, so no deletion phenotype has been reported specifically for this gene (bitton2011augmentedannotationof pages 8-10).
Tam14 belongs to the RAMP4 protein family (Pfam PF06624) and carries an ER stress-associated domain (InterPro IPR010580). This family is defined by the mammalian protein RAMP4 (Ribosome-Associated Membrane Protein 4), also known as SERP1 (Stress-associated Endoplasmic Reticulum Protein 1), and the Saccharomyces cerevisiae ortholog Ysy6 (lewis2024structuralanalysisof pages 1-2).
Structural characterization of mammalian RAMP4 reveals a small (~7 kDa) protein with two key structural domains: (i) a hook-shaped ribosome-binding domain (RBD) consisting of an N-terminal α-helix flanked by 3₁₀-helices, which binds 28S rRNA and ribosomal proteins eL19, eL22, and eL31 through electrostatic and hydrophobic interactions; and (ii) a kinked transmembrane domain (TMD) connected to the RBD by a flexible linker (lewis2024structuralanalysisof pages 4-6). The TMD is kinked approximately 40° at a conserved glycine residue. The cytoplasmic half of the TMD is hydrophobic and binds the Sec61 lateral gate, while the lumenal half is amphipathic, with its hydrophilic face oriented toward the channel interior, contributing to the hydrophilic lumenal funnel of the Sec61α subunit (lewis2024structuralanalysisof pages 4-6).
RAMP4 is classified as a tail-anchored (TA) membrane protein and can be targeted to the ER membrane via multiple redundant pathways, including the SRP, SND, and TRC/GET pathways (sicking2021complexityandspecificity pages 9-11).
Based on its RAMP4 family membership and domain architecture, tam14 is predicted to function as a small accessory component of the Sec61 translocon at the endoplasmic reticulum membrane. The following functional inferences are drawn from well-characterized RAMP4/SERP1 orthologs:
Association with the Sec61 translocon: RAMP4 is tightly associated near-stoichiometrically with ER-localized ribosome-Sec61 complexes. Cryo-EM structural analysis has revealed that RAMP4 intercalates into Sec61's lateral gate, widening the central pore and contributing to its hydrophilic interior (lewis2024structuralanalysisof pages 1-2). In native mammalian ER membranes, RAMP4 is present in approximately 81% of non-MPT (multipass translocon)-containing ribosome-translocon complexes, making it a near-constitutive component (lewis2024structuralanalysisof pages 4-6). RAMP4 can be crosslinked to nascent polypeptide chains translocating through the Sec61 channel, indicating direct interaction with substrates during protein translocation (lewis2024structuralanalysisof pages 1-2).
Facilitation of membrane protein integration: The recruitment of RAMP4 to the translocon is triggered when a transmembrane segment enters the ribosomal exit tunnel, where ribosomal protein Rpl17 recognizes the TM segment and signals RAMP4 recruitment. This process helps remodel the translocon to facilitate the switch from translocation mode to membrane integration mode (pool2009atransmembranesegment pages 11-12, pool2009atransmembranesegment pages 1-2, pool2009atransmembranesegment pages 9-11).
"Surrogate signal peptide" function: Lewis et al. (2024) proposed that RAMP4 functions as a "surrogate signal peptide" that maintains the Sec61 pore in a widened, hydrophilic configuration during later stages of translocation, after the original signal peptide has dissociated from the lateral gate. Unlike signal peptides, RAMP4 does not displace the plug helix—the plug moves with the widening pore ring, remaining plugged. This model suggests RAMP4 smooths protein transport through the channel and maintains translocation speed and efficiency for certain protein sequences (lewis2024structuralanalysisof pages 9-11).
Stabilization of membrane proteins and glycosylation: RAMP4/SERP1 has been implicated in stabilizing newly synthesized membrane proteins during ER stress conditions and in facilitating their subsequent N-linked glycosylation (spasic2005posttranslationalinsertionof pages 99-99, pool2009atransmembranesegment pages 1-2). This protective function becomes particularly critical under conditions of high secretory activity or ER stress.
By family inference, tam14 is predicted to localize to the endoplasmic reticulum membrane, specifically at the ribosome-associated Sec61 translocon on the rough ER. RAMP4 family members are integral ER membrane proteins that associate with active ribosome-translocon complexes, positioning them at the interface between the cytoplasmic ribosome and the ER translocation channel (lewis2024structuralanalysisof pages 1-2, lewis2024structuralanalysisof pages 4-6). No direct localization data for tam14 in S. pombe cells has been reported.
ER protein biogenesis pathway: The primary pathway in which tam14 is predicted to function is the co-translational protein translocation and membrane insertion pathway at the ER. This pathway involves the Sec61 translocon, the signal recognition particle (SRP) system, the oligosaccharyltransferase (OST) complex, the TRAP complex, and various accessory factors including RAMP4 family members (sicking2021complexityandspecificity pages 4-7, sicking2021complexityandspecificity pages 9-11).
ER stress response: RAMP4/SERP1 expression in mammals is strongly upregulated by ER stress-responsive transcription factors XBP1 and Hac1p, and animals lacking RAMP4 exhibit induction of the unfolded protein response (UPR) in secretory tissues such as the pancreas and pituitary gland (pool2009atransmembranesegment pages 11-12). Notably, the UPR in S. pombe differs fundamentally from both S. cerevisiae and mammalian cells: S. pombe lacks Hac1/XBP1 orthologs and instead relies primarily on Ire1-dependent mRNA decay (RIDD) rather than transcriptional upregulation to cope with ER stress (lewis2024structuralanalysisof pages 1-2). This means that the mechanism of tam14 transcriptional regulation during ER stress in S. pombe may differ from the canonical RAMP4/SERP1 paradigm in mammals.
Meiotic expression pattern: The "tam" designation reflects the observation that tam14 transcript levels change during the meiotic differentiation program in S. pombe, as detected in pat1.114-induced synchronous meiotic cultures (bitton2011augmentedannotationof pages 1-2, bitton2011augmentedannotationof pages 8-10). This meiotic expression pattern could reflect increased demand for ER-associated protein biogenesis during sporulation and ascospore formation, processes that require substantial membrane remodeling and protein secretion. However, the meiotic expression change alone does not imply a meiosis-specific biochemical function.
The functional annotation of tam14 rests primarily on domain and family-level inference from well-characterized orthologs (RAMP4/SERP1 in mammals, Ysy6 in S. cerevisiae), rather than on direct experimental characterization of the S. pombe gene product itself. The gene was identified and its transcription confirmed in the Bitton et al. (2011) genome re-annotation study (bitton2011augmentedannotationof pages 1-2, bitton2011augmentedannotationof pages 8-10), but no targeted deletion, localization, or biochemical study has been published specifically for tam14/SPCC330.20. The structural and functional characterization of RAMP4 orthologs—particularly recent cryo-EM work by Lewis et al. (2024) showing RAMP4 intercalated in the Sec61 lateral gate (lewis2024structuralanalysisof pages 1-2, lewis2024structuralanalysisof pages 4-6, lewis2024structuralanalysisof pages 9-11) and earlier work by Pool (2009) demonstrating TM segment-triggered recruitment (pool2009atransmembranesegment pages 11-12, pool2009atransmembranesegment pages 1-2, pool2009atransmembranesegment pages 9-11)—provides a strong basis for inferring that tam14 serves an analogous role as an accessory Sec61 translocon component in S. pombe.
The following table summarizes the key properties of tam14:
| Property | Description/Value |
|---|---|
| Gene name | tam14; one of the 14 S. pombe loci named for having transcripts altered during meiosis in the augmented genome annotation study (bitton2011augmentedannotationof pages 8-10) |
| Systematic name | SPCC330.20 (UniProt entry provided by user; also listed in the augmented annotation table as the locus corresponding to tam14) (bitton2011augmentedannotationof pages 3-4) |
| UniProt accession | G2TRT3 (user-supplied UniProt identifier) |
| Organism | Schizosaccharomyces pombe strain 972 / ATCC 24843 (fission yeast) (user-supplied target definition) |
| Protein description | Protein tam14; alternative name: Transcripts altered in meiosis protein 14 (user-supplied target definition) |
| Evidence for existence in S. pombe | The locus was identified in the 2011 re-annotation of the S. pombe genome; transcription was supported by RT-PCR/RNA-seq in the study’s global validation pipeline, but tam14 was not among the genes selected for functional knockout characterization (bitton2011augmentedannotationof pages 1-2, bitton2011augmentedannotationof pages 8-10) |
| Protein family | RAMP4 family / ER stress-associated small membrane proteins; family-level functional inference is supported by RAMP4/SERP1 literature and domain assignment (lewis2024structuralanalysisof pages 4-6, lewis2024structuralanalysisof pages 1-2) |
| Domain annotations | RAMP4 / PF06624 and ER_stress-assoc. / IPR010580; in the Bitton et al. annotation table tam14 is associated with a Pfam-supported novel locus (bitton2011augmentedannotationof pages 3-4, bitton2011augmentedannotationof pages 8-10) |
| Predicted molecular role | Likely a small ER membrane accessory factor of the Sec61 ribosome-translocon complex, inferred from the conserved RAMP4 family: RAMP4/SERP1 associates near-stoichiometrically with ER-localized ribosome-Sec61 complexes and can contact translocating nascent chains (lewis2024structuralanalysisof pages 1-2) |
| Predicted mechanistic function | By family inference, likely helps optimize membrane protein biogenesis at the ER, especially during or after translocon remodeling for membrane protein insertion; RAMP4 is recruited when a TM segment enters the ribosome exit tunnel and can facilitate the switch to membrane integration mode (pool2009atransmembranesegment pages 11-12, pool2009atransmembranesegment pages 1-2) |
| Predicted structural behavior | RAMP4-family proteins contain a ribosome-binding region and a tail-anchored/kinked TM segment that occupies the Sec61 lateral gate, widens the central pore, and contributes to the channel’s hydrophilic interior; tam14 is therefore plausibly a very small ER membrane protein with analogous architecture (lewis2024structuralanalysisof pages 4-6) |
| Predicted subcellular localization | Endoplasmic reticulum membrane, specifically the ribosome-associated Sec61 translocon at rough ER, by conserved family function (lewis2024structuralanalysisof pages 4-6, lewis2024structuralanalysisof pages 1-2, sicking2021complexityandspecificity pages 9-11) |
| Pathway context | Likely functions in co-translational ER protein translocation/membrane insertion and broader ER proteostasis rather than a meiosis-specific biochemical pathway; the meiosis-linked name reflects expression behavior, not proven primary function (bitton2011augmentedannotationof pages 8-10, sicking2021complexityandspecificity pages 9-11) |
| Relation to ER stress | Family inference suggests involvement in ER stress adaptation: mammalian RAMP4/SERP1 is ER-stress inducible and loss causes secretion/UPR phenotypes in secretory tissues; however, this has not been directly demonstrated for tam14 in S. pombe (pool2009atransmembranesegment pages 11-12, lewis2024structuralanalysisof pages 1-2) |
| Orthologs / homologous family members | Mammals: RAMP4 / SERP1; budding yeast: Ysy6; these are the relevant family comparators for functional inference to tam14 (lewis2024structuralanalysisof pages 1-2, sicking2021complexityandspecificity pages 9-11) |
| Functional confidence level | Moderate for family-level annotation, low for gene-specific detail: there is strong domain/family evidence, but little direct experimental characterization specific to tam14/SPCC330.20 itself (bitton2011augmentedannotationof pages 8-10, lewis2024structuralanalysisof pages 4-6, lewis2024structuralanalysisof pages 1-2) |
| Key evidence sources | Primary S. pombe identification: Bitton et al. 2011 genome re-annotation (bitton2011augmentedannotationof pages 1-2, bitton2011augmentedannotationof pages 8-10); mechanistic family context: Pool 2009 and Lewis et al. 2024 on RAMP4/Sec61 structure-function (pool2009atransmembranesegment pages 11-12, lewis2024structuralanalysisof pages 4-6, lewis2024structuralanalysisof pages 1-2) |
Table: This table summarizes the verified identity, annotation, predicted function, and likely localization of tam14/SPCC330.20 in fission yeast. It distinguishes direct evidence for the S. pombe gene from family-based inference drawn from better-characterized RAMP4/SERP1 proteins.
The principal sources supporting this report include Bitton et al. (2011) Genetics 187:1207–1217, which identified tam14 as a novel gene in S. pombe; Lewis et al. (2024) eLife 13, which provided cryo-EM structures of RAMP4 at the Sec61 translocon; and Pool (2009) J. Cell Biol. 185:889–902, which characterized RAMP4 recruitment mechanisms.
References
(bitton2011augmentedannotationof pages 1-2): Danny A Bitton, Valerie Wood, Paul J Scutt, Agnes Grallert, Tim Yates, Duncan L Smith, Iain M Hagan, and Crispin J Miller. Augmented annotation of the schizosaccharomyces pombe genome reveals additional genes required for growth and viability. Genetics, 187:1207-1217, Apr 2011. URL: https://doi.org/10.1534/genetics.110.123497, doi:10.1534/genetics.110.123497. This article has 32 citations and is from a domain leading peer-reviewed journal.
(bitton2011augmentedannotationof pages 3-4): Danny A Bitton, Valerie Wood, Paul J Scutt, Agnes Grallert, Tim Yates, Duncan L Smith, Iain M Hagan, and Crispin J Miller. Augmented annotation of the schizosaccharomyces pombe genome reveals additional genes required for growth and viability. Genetics, 187:1207-1217, Apr 2011. URL: https://doi.org/10.1534/genetics.110.123497, doi:10.1534/genetics.110.123497. This article has 32 citations and is from a domain leading peer-reviewed journal.
(bitton2011augmentedannotationof pages 8-10): Danny A Bitton, Valerie Wood, Paul J Scutt, Agnes Grallert, Tim Yates, Duncan L Smith, Iain M Hagan, and Crispin J Miller. Augmented annotation of the schizosaccharomyces pombe genome reveals additional genes required for growth and viability. Genetics, 187:1207-1217, Apr 2011. URL: https://doi.org/10.1534/genetics.110.123497, doi:10.1534/genetics.110.123497. This article has 32 citations and is from a domain leading peer-reviewed journal.
(lewis2024structuralanalysisof pages 1-2): Aaron J. O. Lewis, Frank Zhong, Robert J. Keenan, and Ramanujan S. Hegde. Structural analysis of the dynamic ribosome-translocon complex. eLife, May 2024. URL: https://doi.org/10.1101/2023.12.22.572959, doi:10.1101/2023.12.22.572959. This article has 23 citations and is from a domain leading peer-reviewed journal.
(lewis2024structuralanalysisof pages 4-6): Aaron J. O. Lewis, Frank Zhong, Robert J. Keenan, and Ramanujan S. Hegde. Structural analysis of the dynamic ribosome-translocon complex. eLife, May 2024. URL: https://doi.org/10.1101/2023.12.22.572959, doi:10.1101/2023.12.22.572959. This article has 23 citations and is from a domain leading peer-reviewed journal.
(sicking2021complexityandspecificity pages 9-11): Mark Sicking, Sven Lang, Florian Bochen, Andreas Roos, Joost P. H. Drenth, Muhammad Zakaria, Richard Zimmermann, and Maximilian Linxweiler. Complexity and specificity of sec61-channelopathies: human diseases affecting gating of the sec61 complex. Cells, 10:1036, Apr 2021. URL: https://doi.org/10.3390/cells10051036, doi:10.3390/cells10051036. This article has 48 citations.
(pool2009atransmembranesegment pages 11-12): Martin R. Pool. A trans-membrane segment inside the ribosome exit tunnel triggers ramp4 recruitment to the sec61p translocase. The Journal of Cell Biology, 185:889-902, Jun 2009. URL: https://doi.org/10.1083/jcb.200807066, doi:10.1083/jcb.200807066. This article has 67 citations.
(pool2009atransmembranesegment pages 1-2): Martin R. Pool. A trans-membrane segment inside the ribosome exit tunnel triggers ramp4 recruitment to the sec61p translocase. The Journal of Cell Biology, 185:889-902, Jun 2009. URL: https://doi.org/10.1083/jcb.200807066, doi:10.1083/jcb.200807066. This article has 67 citations.
(pool2009atransmembranesegment pages 9-11): Martin R. Pool. A trans-membrane segment inside the ribosome exit tunnel triggers ramp4 recruitment to the sec61p translocase. The Journal of Cell Biology, 185:889-902, Jun 2009. URL: https://doi.org/10.1083/jcb.200807066, doi:10.1083/jcb.200807066. This article has 67 citations.
(lewis2024structuralanalysisof pages 9-11): Aaron J. O. Lewis, Frank Zhong, Robert J. Keenan, and Ramanujan S. Hegde. Structural analysis of the dynamic ribosome-translocon complex. eLife, May 2024. URL: https://doi.org/10.1101/2023.12.22.572959, doi:10.1101/2023.12.22.572959. This article has 23 citations and is from a domain leading peer-reviewed journal.
(spasic2005posttranslationalinsertionof pages 99-99): Milan Spasic. Post-translational insertion of a small tail-anchored protein into the membrane of the endoplasmic reticulum. ArXiv, Jan 2005. URL: https://doi.org/10.11588/heidok.00005525, doi:10.11588/heidok.00005525. This article has 0 citations.
(sicking2021complexityandspecificity pages 4-7): Mark Sicking, Sven Lang, Florian Bochen, Andreas Roos, Joost P. H. Drenth, Muhammad Zakaria, Richard Zimmermann, and Maximilian Linxweiler. Complexity and specificity of sec61-channelopathies: human diseases affecting gating of the sec61 complex. Cells, 10:1036, Apr 2021. URL: https://doi.org/10.3390/cells10051036, doi:10.3390/cells10051036. This article has 48 citations.