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Queuine is incorporated into brain transfer RNA
T J Siard1, J R Katze, W R Farkas
1University of Tennessee College of Veterinary Medicine, Knoxville 37901-1071.
Neurochemical Research
|November 1, 1989
Summary
Queuine, a modified guanine base, is present in nearly all Q-family tRNAs in pig brains. This indicates queuine crosses the blood-brain barrier and the brain has the necessary enzyme for this base modification.
Area of Science:
- Biochemistry
- Molecular Biology
- Neuroscience
Background:
- Transfer RNA (tRNA) plays a crucial role in protein synthesis.
- Modified nucleosides in tRNA, like queuosine, can impact translation fidelity.
- The presence and role of queuosine in mammalian brain tRNA are not fully understood.
Purpose of the Study:
- To investigate the presence and extent of queuosine modification in pig brain tRNA.
- To determine if queuosine can cross the blood-brain barrier.
- To identify the presence of guanine-queuine tRNA transglycosylase in the brain.
Main Methods:
- Assaying pig brain tRNA for queuosine in the anticodon of Q-family tRNAs (Asp, Asn, His, Tyr).
- Aminoacylating tRNA with the respective amino acids.
- Analyzing aminoacylated tRNAs using RPC-5 chromatography.
- Confirming queuosine presence via chemical modification (BrCN or NaIO4) and altered RPC-5 elution profiles.
Main Results:
- Queuine was found to substitute for guanine in virtually 100% of the anticodons for all four Q-family tRNAs.
- The elution profiles from RPC-5 chromatography confirmed the presence of queuine.
- Chemical treatments (BrCN, NaIO4) resulted in predictable changes to the elution profiles, validating the findings.
Conclusions:
- Queuine successfully crosses the blood-brain barrier into the pig brain.
- The pig brain possesses active guanine-queuine tRNA transglycosylase, the enzyme responsible for guanine replacement with queuine.
- This extensive modification suggests a significant role for queuosine in brain function and translation.