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Results for “Small open reading frame (sORF)”

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PubMed2025

Cellular function of the GndA microprotein during heat shock.

Over the past 15 years, hundreds of previously undiscovered bacterial small open reading frames (sORFs) encoding microproteins of fewer than fifty amino acids have been identified. Biological functions have been ascribed to an increasing number of microproteins from intergenic regions and small RNAs, and many play integral roles in bacterial stress responses. However, despite numbering in the dozens in Escherichia coli, and hundreds in humans, same-strand frameshifted sORFs that internally overlap protein coding sequences remain understudied. To provide insight into nested genes, we characterized GndA, a frameshifted 36-amino acid microprotein nested within the 6-phosphogluconate dehydrogenase (6PGD) coding sequence. Using precise genome editing, we demonstrate independent contributions of GndA and 6PGD to cell growth at high temperature. GndA associates with membrane-associated complexes associated with electron transport and ATP generation, and supports ATP homeostasis during heat shock. Functional characterization of GndA thus adds to the catalog of bacterial microproteins that function in stress responses, while providing clear genetic evidence for the importance of an overlapping gene to cellular fitness.

6PGD↗

PubMed2026

An immune-associated mitochondrial DNA variant with sex differences reveals a putative novel microprotein called MASL.

The use of mitochondrial wide association studies (MiWAS) to link mitochondrial DNA variants (mtSNPs) to phenotypes of interest has uncovered important connections between mitochondrial genes and human health. The recent introduction of a re-annotated mitochondrial genome that accounts for small open reading frames (sORFs) with protein coding potential suggests the existence of mitochondrial-derived microproteins, many of which remain uncharacterized. Thus, considering the re-annotated mitochondrial genome when conducting genomic analyses such as MiWAS facilitates the mapping of mtSNPs back to microprotein-encoding sORFs and uncovers interactions between mitochondrial microproteins and biological systems. Here, we employ MiWAS of venous blood samples from the Health and Retirement Study (HRS) and identify a mtSNP associated with sex-specific changes to immune composition. After accounting for re-annotation, we map the identified mtSNP back to a sORF that encodes a novel microprotein, termed MASL (Mitochondrial Associated Small d-Loop peptide). Complementary phenome-wide association studies (PheWAS) in HRS and and UK Biobank confirm interactions between this mtSNP and immune phenotypes of interest, and our targeted RNA-Seq method (mitoSNP-seq) elucidates sex-differences in gene expression and functional pathways potentially altered by this mtSNP that may be relevant to the associated microprotein. Early characterization of the MASL microprotein shows sex-differences in circulating MASL levels in human plasma, and sex-specific interactions when comparing male and female mice treated with synthesized MASL. Together, the results of this study not only contribute to our understanding of mitochondrial dynamics in immunity, but also provide early characterization of a novel mitochondrial-derived microprotein with sex-specific modulatory effects.

Genomics↗

PubMed2026

The mighty microproteins: from versatile cellular regulators to precision medicine therapeutics.

Microproteins, are tiny proteins encoded by small open reading frame (sORF), translation of these non-canonical open reading frames (ncORFs) has been implicated in diverse biological processes and diseases. This review summarizes recent developments in the discovery, biogenesis, and functional characterization of microproteins, and their involvement in various disease, with special focus on their roles in cancer, cardiovascular, metabolic, neurodegenerative and immune-related disorders. We emphasize the regulation of key cellular pathways by microproteins, including mitochondrial homeostasis, apoptosis, metabolic reprogramming, and immune signaling, all of which affect disease initiation and progression. Emerging evidence also supports their potential as disease biomarkers and therapeutic candidates for precision medicine. Finally, the review critically discusses the current challenges including discrepancies in microprotein annotation, the limitations of ribosome profiling and proteogenomic approaches, the gap between computationally predicted and experimentally validated microproteins, and the need for rigorous orthogonal validation by means of CRISPR-based genome editing, ribosome release assays, mutational analysis, high-resolution mass spectrometry, and functional studies. Finally, we review recent development of AI-assisted ORF prediction, single-cell translatomics, spatial proteomics, and integrated multi-omics as emerging technologies reshaping. Microprotein discovery and functional annotation. Finally, we discuss the translational potential of microproteins and highlight the remaining challenges to clinical application, including peptide stability, pharmacokinetics, tissue-specific delivery, immunogenicity, and the need for rigorous preclinical and clinical validation. Together, this review provides an updated and critical overview of the rapidly evolving microprotein field and highlights future research priorities for translating these molecules into clinically useful biomarkers and precision therapeutics.

Microproteins↗

PubMed2026

Micropeptides encoded by lncRNAs associated with cancer progression reveal novel immunogenic epitopes.

MOTIVATION: Long non-coding RNAs (lncRNAs) regulate gene expression, chromatin organization, and cellular signaling. Recent studies indicate that ∼20% of the ∼36 000 human lncRNA genes harbor small open reading frames (sORFs) capable of producing micropeptides (MPs), whose functions remain largely unknown. Whether these peptides contribute to the cancer immunopeptidome is largely unexplored. RESULTS: We systematically analyzed lncRNAs with strong experimental and computational evidence of MP-encoding potential (∼13% of the initial MP collection). Using The Cancer Genome Atlas (TCGA), we identified 2606 high-confidence lncRNA-derived MPs encoded by 647 genes across 16 cancer types. We then focused on 501 MPs from 124 lncRNA genes whose expression changes significantly across tumor stages and metastatic transitions, representing cancer transitional lncRNAs (Tr-lncRNAs). Dipeptide composition and conservation analyses showed that these MPs differ from a size-matched human coding proteome, supporting their potential as neoantigens. All possible 9-mer peptides were evaluated for predicted binding to prevalent European HLA class I alleles. Approximately 60% of Tr-lncRNA genes and 184 (37%) of derived peptides exhibited strong predicted HLA binding. Peptides from XIST, PCAT7, PVT1, HAND2-AS1 showed broad HLA coverage. Notably, TTN-AS1, encoded an MP (79 aa) generated 33 predicted distinct epitopes spanning all 27 HLA alleles. Our analysis identifies lncRNA-derived MPs as a previously underexplored source of potential cancer neoantigens, highlighting their promise as biomarkers and targets for immunotherapy. AVAILABILITY: Data, code and supplementary materials are available in https://doi.org/10.5281/zenodo.20167452 and GitHub: https://github.com/stavzok1/lncrna_peptide_analysis.

Humans↗

PubMed2026

IRES-like element-mediated translation of vsp1S4(-) suppresses BmCPV replication via RNAi antagonism.

Double-stranded RNA (dsRNA) viruses are thought to express proteins exclusively from their sense strand, while the antisense strand serves primarily as a replication template. Whether the antisense strand harbors hidden coding potential remains largely unexplored. Here, by integrating ribosome profiling and mass spectrometry, we identify a conserved 78-amino acid microprotein, vsp1S4(-), encoded by an antisense small open reading frame (sORFs) of the Bombyx mori cypovirus (BmCPV) genome. We demonstrate that vsp1S4(-) translation is driven by a previously unrecognized IRES-like element. Functional characterizations reveal that vsp1S4(-) localizes to the plasma membrane and acts as a negative regulator of viral replication. Mechanistically, vsp1S4(-) interacts directly with the viral RNAi suppressor NSP8, competitively disrupting the NSP8-AGO2 complex. This action restores the host's antiviral RNAi response, thereby limiting viral proliferation. Our findings challenge the conventional view of dsRNA virus coding capacity, unveil a novel viral immune evasion and replication control mechanism, and highlight antisense-encoded microproteins as potential targets for antiviral therapy.

Animals↗

PubMed2024

Mapping Start Codons of Small Open Reading Frames by N-Terminomics Approach.

sORF-encoded peptides (SEPs) refer to proteins encoded by small open reading frames (sORFs) with a length of less than 100 amino acids, which play an important role in various life activities. Analysis of known SEPs showed that using non-canonical initiation codons of SEPs was more common. However, the current analysis of SEP sequences mainly relies on bioinformatics prediction, and most of them use AUG as the start site, which may not be completely correct for SEPs. Chemical labeling was used to systematically analyze the N-terminal sequences of SEPs to accurately define the start sites of SEPs. By comparison, we found that dimethylation and guanidinylation are more efficient than acetylation. The ACN precipitation and heating precipitation performed better in SEP enrichment. As an N-terminal peptide enrichment material, Hexadhexaldehyde was superior to CNBr-activated agarose and NHS-activated agarose. Combining these methods, we identified 128 SEPs with 131 N-terminal sequences. Among them, two-thirds are novel N-terminal sequences, and most of them start from the 11-31st amino acids of the original sequence. Partial novel N-termini were produced by proteolysis or signal peptide removal. Some SEPs' transcription start sites were corrected to be non-AUG start codons. One novel start codon was validated using GFP-tag vectors. These results demonstrated that the chemical labeling approaches would be beneficial for identifying the start codons of sORFs and the real N-terminal of their encoded peptides, which helps better understand the characterization of SEPs.

Open Reading Frames↗

PubMed2025

Popcorn: prediction of short coding and noncoding genomic sequences in prokaryotes.

SUMMARY: The most challenging prokaryotic genes to identify often correspond to short ORFs (sORFs) encoding small proteins or to noncoding RNAs. RNA-seq experiments commonly evince small transcripts that do not correspond to annotated genes and are candidates for novel coding sORFs or small regulatory RNAs, but it can be difficult to accurately assess whether the numerous small transcripts are coding or not. We present Popcorn (PrOkaryotic Prediction of Coding OR Noncoding), a novel machine learning method for determining whether prokaryotic sequences are coding or noncoding. We find that Popcorn is effective in distinguishing coding from noncoding sequences, including coding sORFs and noncoding RNAs. AVAILABILITY AND IMPLEMENTATION: Freely available for use on the web at https://cs.wellesley.edu/∼btjaden/Popcorn. Source code available at https://github.com/btjaden/Popcorn and https://doi.org/10.5281/zenodo.15120075.

Open Reading Frames↗