orb

UniProt ID: Q8IMZ2
Organism: Drosophila melanogaster
Review Status: IN PROGRESS
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Gene Description

Orb is a cytoplasmic polyadenylation element-binding protein that recognizes sequences in mRNA 3-prime untranslated regions and controls maternal mRNA translation and localization. It is enriched in the developing oocyte, where its post-transcriptional regulation supports germline development and establishment of oocyte polarity. Its C-terminal RNA-recognition region is conserved in the shorter Q8IMZ2 form.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0003676 nucleic acid binding
IEA
GO_REF:0000002
MODIFY
Summary: Orb recognizes cytoplasmic polyadenylation elements in mRNA 3-prime untranslated regions. This experimentally defined RNA target makes mRNA 3-prime-UTR binding more informative than the generic nucleic-acid or RNA-binding annotation.
Reason: Orb recognizes cytoplasmic polyadenylation elements in mRNA 3-prime untranslated regions. This experimentally defined RNA target makes mRNA 3-prime-UTR binding more informative than the generic nucleic-acid or RNA-binding annotation.
Proposed replacements: mRNA 3'-UTR binding
Supporting Evidence:
PMID:27791065
Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
GO:0003723 RNA binding
IEA
GO_REF:0000120
MODIFY
Summary: Orb recognizes cytoplasmic polyadenylation elements in mRNA 3-prime untranslated regions. This experimentally defined RNA target makes mRNA 3-prime-UTR binding more informative than the generic nucleic-acid or RNA-binding annotation.
Reason: Orb recognizes cytoplasmic polyadenylation elements in mRNA 3-prime untranslated regions. This experimentally defined RNA target makes mRNA 3-prime-UTR binding more informative than the generic nucleic-acid or RNA-binding annotation.
Proposed replacements: mRNA 3'-UTR binding
Supporting Evidence:
PMID:27791065
Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
GO:0003729 mRNA binding
TAS
PMID:11700288
Translational regulation and RNA localization in Drosophila ...
MODIFY
Summary: Orb recognizes cytoplasmic polyadenylation elements in mRNA 3-prime untranslated regions. This experimentally defined RNA target makes mRNA 3-prime-UTR binding more informative than the generic nucleic-acid or RNA-binding annotation.
Reason: Orb recognizes cytoplasmic polyadenylation elements in mRNA 3-prime untranslated regions. This experimentally defined RNA target makes mRNA 3-prime-UTR binding more informative than the generic nucleic-acid or RNA-binding annotation.
Proposed replacements: mRNA 3'-UTR binding
Supporting Evidence:
PMID:27791065
Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
GO:0003730 mRNA 3'-UTR binding
IEA
GO_REF:0000002
ACCEPT
Summary: Direct binding profiles establish recognition of CPE-like sequences in mRNA 3-prime UTRs. The selected shorter Orb sequence retains the complete C-terminal RNA-binding region.
Reason: Direct binding profiles establish recognition of CPE-like sequences in mRNA 3-prime UTRs. The selected shorter Orb sequence retains the complete C-terminal RNA-binding region.
Supporting Evidence:
PMID:27791065
Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
GO:0005737 cytoplasm
IDA
PMID:10101171
The posterior determinant gene nanos is required for the mai...
ACCEPT
Summary: Primary imaging localizes Orb to the cytoplasm of the germline cyst and enriches it in the oocyte. This directly supports the broad cytoplasmic localization.
Reason: Primary imaging localizes Orb to the cytoplasm of the germline cyst and enriches it in the oocyte. This directly supports the broad cytoplasmic localization.
Supporting Evidence:
PMID:11809824
ORB is found in the cytoplasm of each cell of the 16-cell cyst; furthermore, it shows enrichment in the oocyte in late region 2a or early region 2b
GO:0005737 cytoplasm
IEA
GO_REF:0000044
ACCEPT
Summary: Primary imaging localizes Orb to the cytoplasm of the germline cyst and enriches it in the oocyte. This directly supports the broad cytoplasmic localization.
Reason: Primary imaging localizes Orb to the cytoplasm of the germline cyst and enriches it in the oocyte. This directly supports the broad cytoplasmic localization.
Supporting Evidence:
PMID:11809824
ORB is found in the cytoplasm of each cell of the 16-cell cyst; furthermore, it shows enrichment in the oocyte in late region 2a or early region 2b
GO:0006417 regulation of translation
IEA
GO_REF:0000002
ACCEPT
Summary: Orb binds target mRNAs and controls their translation in the female germline. The conserved RNA-binding machinery in the selected form supports the broad regulator activity, without assuming identical regulation of all isoforms.
Reason: Orb binds target mRNAs and controls their translation in the female germline. The conserved RNA-binding machinery in the selected form supports the broad regulator activity, without assuming identical regulation of all isoforms.
Supporting Evidence:
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
PMID:27791065
Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
GO:0007281 germ cell development
IMP
PMID:11809824
Cytoplasmic localization and evolutionary conservation of ME...
KEEP AS NON CORE
Summary: The primary MEI-218 study directly examines orb-mutant germline cysts and supports an Orb requirement in oocyte development. This developmental consequence is retained as noncore relative to sequence-specific translational regulation.
Reason: The primary MEI-218 study directly examines orb-mutant germline cysts and supports an Orb requirement in oocyte development. This developmental consequence is retained as noncore relative to sequence-specific translational regulation.
Supporting Evidence:
PMID:11809824
ORB is found in the cytoplasm of each cell of the 16-cell cyst; furthermore, it shows enrichment in the oocyte in late region 2a or early region 2b
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
GO:0007310 oocyte dorsal/ventral axis specification
IMP
PMID:15737929
The Drosophila fragile X protein functions as a negative reg...
KEEP AS NON CORE
Summary: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Reason: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Supporting Evidence:
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
PMID:7926753
orb is required for the asymmetric distribution of oskar and gurken mRNAs within the oocyte during the later stages of oogenesis.
GO:0007310 oocyte dorsal/ventral axis specification
IMP
PMID:7926753
orb is required for anteroposterior and dorsoventral pattern...
KEEP AS NON CORE
Summary: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Reason: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Supporting Evidence:
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
PMID:7926753
orb is required for the asymmetric distribution of oskar and gurken mRNAs within the oocyte during the later stages of oogenesis.
GO:0007314 oocyte anterior/posterior axis specification
IMP
PMID:7926753
orb is required for anteroposterior and dorsoventral pattern...
KEEP AS NON CORE
Summary: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Reason: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Supporting Evidence:
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
PMID:7926753
orb is required for the asymmetric distribution of oskar and gurken mRNAs within the oocyte during the later stages of oogenesis.
GO:0045182 translation regulator activity
IEA
GO_REF:0000002
ACCEPT
Summary: Orb binds target mRNAs and controls their translation in the female germline. The conserved RNA-binding machinery in the selected form supports the broad regulator activity, without assuming identical regulation of all isoforms.
Reason: Orb binds target mRNAs and controls their translation in the female germline. The conserved RNA-binding machinery in the selected form supports the broad regulator activity, without assuming identical regulation of all isoforms.
Supporting Evidence:
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
PMID:27791065
Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
GO:0045451 germ plasm oskar mRNA localization
IMP
PMID:7926753
orb is required for anteroposterior and dorsoventral pattern...
KEEP AS NON CORE
Summary: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Reason: Orb-dependent post-transcriptional regulation supports oocyte polarity and localization of maternal determinants, including oskar RNA. Retain the experimentally supported developmental/localization consequence as noncore relative to its direct RNA-binding and translational-regulatory mechanism.
Supporting Evidence:
PMID:15737929
Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
PMID:7926753
orb is required for the asymmetric distribution of oskar and gurken mRNAs within the oocyte during the later stages of oogenesis.

Core Functions

Recognizes CPE-like elements in target mRNA 3-prime UTRs to regulate cytoplasmic translation.

Directly Involved In:
Cellular Locations:
Supporting Evidence:
  • PMID:27791065
    Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity.
  • PMID:15737929
    Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte.
  • file:DROME/orb/orb-bioinformatics/RESULTS.md
    The complete 552-residue C-terminal region (target 8–559, reference 364–915) is identical.

References

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External Prediction Reviews

These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.

ProtNLM2 External predictions

View prediction review YAML Β· orb-protnlm-predictions-review.yaml Β· Review status: COMPLETE

Orb is an experimentally established CPEB-family RNA-binding translation regulator, and the same GO term already occurs in the selected record.

Source documents: genes/DROME/orb/orb-predictions-source.json Β· genes/DROME/orb/orb-uniprot-source.json

Review score: 2 = concordant with evidence; 1 = uncertain; 0 = discordant with evidence. This is an assessment score, not a model probability.

GO:0045182 translation regulator activity GO_MF
CNN β€” Correct but not novel Review score: 2/2
Prediction method: ProtNLM2 Β· Version: UniProt API snapshot 2026-09-08 Β· file:DROME/orb/orb-predictions-source.json
Review rationale: Orb is an experimentally established CPEB-family RNA-binding translation regulator, and the same GO term already occurs in the selected record. Direct RNA-target profiling and germline translational studies support correctness independently of that electronic annotation. Q8IMZ2 is shorter at the N-terminus but retains the complete C-terminal RNA-binding machinery, making transfer of this broad function reasonable. The prediction adds no novel activity.
Supporting Evidence:
  • PMID:27791065: "Both Orb and Orb2 bind linear cytoplasmic polyadenylation element-like sequences in the 3' UTRs of largely overlapping target mRNAs, with Orb2 potentially having a broader specificity."
  • PMID:15737929: "Orb is responsible for mediating the translational activation of mRNAs localized within the developing oocyte."
  • file:DROME/orb/orb-bioinformatics/RESULTS.md: "The complete 552-residue C-terminal region (target 8–559, reference 364–915) is identical."

Deep Research

Falcon

(orb-deep-research-falcon.md)

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Manual

(orb-deep-research-manual.md)

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πŸ“š Additional Documentation

Notes

(orb-notes.md)

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Bioinformatics Results

(RESULTS.md)

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πŸ“„ View Raw YAML

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