SNORD3A (U3 snoRNA) is a C/D box small nucleolar RNA essential for ribosome biogenesis. Unlike typical C/D box snoRNAs that guide 2'-O-methylation, U3 snoRNA guides site-specific cleavage of pre-rRNA through base-pairing interactions. It is a critical component of the SSU-processome complex that directs maturation of 18S rRNA and assembly of the 40S small ribosomal subunit. This gene is also known as U3 snoRNA and is atypical among C/D box snoRNAs because it guides pre-rRNA cleavage rather than 2'-O-methylation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0042134 rRNA primary transcript binding | TAS PMID:21349877 The initial U3 snoRNA:pre-rRNA base pairing interaction requ... | ACCEPT | Summary: U3 snoRNA binds to pre-rRNA through multiple base-pairing interactions that are essential for pre-18S rRNA folding Reason: This is a core molecular function of U3 snoRNA well-supported by experimental evidence showing direct base-pairing with rRNA primary transcripts Supporting Evidence: PMID:21349877 the U3 snoRNA is required for folding of the pre-18S rRNA by in vivo chemical probing |
| GO:0070181 small ribosomal subunit rRNA binding | TAS PMID:31996908 Synergistic defects in pre-rRNA processing from mutations in... | ACCEPT | Summary: U3 snoRNA binds specifically to small ribosomal subunit (18S) rRNA sequences during ribosome biogenesis Reason: Well-established function of U3 in binding SSU rRNA, distinct from its role in binding the primary transcript Supporting Evidence: PMID:31996908 U3 snoRNA and the associated Rrp9/U3-55K protein are essential for 18S rRNA production by the SSU-processome complex |
| GO:0030490 maturation of SSU-rRNA | TAS PMID:31996908 Synergistic defects in pre-rRNA processing from mutations in... | ACCEPT | Summary: U3 snoRNA is essential for maturation of the small ribosomal subunit rRNA through directing pre-rRNA cleavages at sites A0, A1, and A2 Reason: Core biological process function with extensive experimental support showing U3 is required for SSU-rRNA maturation Supporting Evidence: PMID:31996908 U3 and Rrp9 are required for early pre-rRNA cleavages at sites A0, A1 and A2 |
| GO:0006364 rRNA processing | TAS PMID:21349877 The initial U3 snoRNA:pre-rRNA base pairing interaction requ... | ACCEPT | Summary: U3 snoRNA guides site-specific cleavage of pre-rRNA, a critical step in rRNA processing Reason: Fundamental role of U3 in rRNA processing through cleavage guidance rather than the typical methylation guidance of other C/D box snoRNAs Supporting Evidence: file:human/SNORD3A/SNORD3A-deep-research-manual.md Unlike typical C/D box snoRNAs that guide 2'-O-methylation, U3 snoRNA plays an essential and unique role in guiding site-specific cleavage of pre-ribosomal RNA during ribosome biogenesis PMID:21349877 Feb 23. The initial U3 snoRNA:pre-rRNA base pairing interaction required for pre-18S rRNA folding revealed by in vivo chemical probing. |
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Download this section (compressed HTML)Q: What are the complete set of protein partners that interact with U3 snoRNA during different stages of ribosome biogenesis?
Q: Are there tissue-specific or developmental stage-specific variants of U3 snoRNA expression or modification that affect ribosome heterogeneity?
Q: How does the observed correlation between SNORD3A levels and prion disease progression relate to ribosome dysfunction or cellular stress pathways?
Experiment: Use SHAPE-MaP or other RNA structure probing methods to map the complete secondary and tertiary structure of human U3 snoRNA in complex with processome proteins
Hypothesis: U3 snoRNA structural domains beyond known base-pairing regions contribute to SSU-processome assembly
Type: Structural analysis
Experiment: Generate human cell lines with specific U3 snoRNA mutations targeting different functional domains and assess pre-rRNA processing kinetics, ribosome production rates, and stress response pathways
Hypothesis: U3 snoRNA variants affect ribosome biogenesis efficiency and cellular stress responses
Type: Functional assay
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