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The cytoplasm of Xenopus oocytes contains a factor that protects double-stranded RNA from adenosine-to-inosine
1Department of Biochemistry, University of Utah, Salt Lake City 84132.
Abstract:
Here we describe studies of double-stranded RNA (dsRNA) adenosine deaminase in Xenopus laevis, in particular during meiotic maturation, the period during which a stage VI oocyte matures to an egg. We show that dsRNA adenosine deaminase is in the nuclei of stage VI oocytes. Most importantly, we demonstrate that the cytoplasm of stage VI oocytes contains a factor that protects microinjected dsRNA from deamination when dsRNA adenosine deaminase is released from the nucleus during meiotic maturation. Our data suggest that the protection factor is a cytoplasmic dsRNA-binding protein or proteins that bind to dsRNA in a sequence-independent manner to occlude dsRNA from binding to dsRNA adenosine deaminase. The cytoplasmic double-stranded RNA-binding protein(s) does not bind to other nucleic acids and can be titrated at high concentrations of dsRNA. These studies raise the question of whether all dsRNA-binding proteins share endogenous substrates and also suggest potential means of regulating dsRNA adenosine deaminase in vivo.
Insights
During Xenopus laevis oocyte maturation, a cytoplasmic factor protects microinjected double-stranded RNA (dsRNA) from deamination. This factor, likely a dsRNA-binding protein, prevents dsRNA adenosine deaminase from acting on the RNA.
Area of Science:
- Molecular Biology
- Developmental Biology
- RNA Biology
Background:
- Double-stranded RNA (dsRNA) adenosine deaminase modifies dsRNA, impacting RNA interference and gene regulation.
- Meiotic maturation in Xenopus laevis oocytes involves significant cellular reorganization and dynamic protein localization.
- Understanding the regulation of dsRNA adenosine deaminase is crucial for comprehending RNA processing during development.
Purpose of the Study:
- To investigate the localization and regulation of dsRNA adenosine deaminase during Xenopus laevis oocyte meiotic maturation.
- To identify factors in the oocyte cytoplasm that may modulate dsRNA adenosine deaminase activity.
- To explore the mechanism by which dsRNA is protected from deamination during this developmental stage.
Main Methods:
- Microinjection of dsRNA into Xenopus laevis stage VI oocytes.
- Analysis of dsRNA adenosine deaminase localization using immunofluorescence.
- Biochemical assays to assess dsRNA deamination and binding interactions.
- Titration experiments to characterize the dsRNA-binding properties of cytoplasmic factors.
Main Results:
- dsRNA adenosine deaminase is primarily localized to the nucleus in stage VI oocytes.
- Upon meiotic maturation, dsRNA adenosine deaminase is released into the cytoplasm.
- The cytoplasm contains a factor that protects microinjected dsRNA from deamination.
- This protective factor appears to be a cytoplasmic dsRNA-binding protein that binds dsRNA sequence-independently.
Conclusions:
- A cytoplasmic dsRNA-binding protein(s) protects microinjected dsRNA from deamination by dsRNA adenosine deaminase during Xenopus oocyte maturation.
- This protection mechanism involves occlusion of dsRNA from the enzyme, likely through sequence-independent binding.
- These findings suggest a novel regulatory mechanism for dsRNA adenosine deaminase in vivo and raise questions about shared substrates among dsRNA-binding proteins.