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Subcellular fractionation and association with the cytoskeleton of messengers encoding myelin proteins
G L Boccaccio1, H Carminatti, D R Colman
1Instituto de Investigaciones Bioquímicas "Fundación Campomar" and Facultad de Ciencias Exactas y Naturales, UBA, Buenos Aires, Argentina. gboccac@iib.uba.ar
Abstract:
The targeting of polypeptides to restricted cytoplasmic domains by means of mRNA sorting is a widespread phenomena utilized by many cell types. In the central nervous system, in situ hybridization analysis has shown previously that the mRNAs encoding several myelin-specific proteins are specifically located within the myelinating processes of oligodendrocytes. Here, by means of biochemical and subcellular fractionation methods, we show that a myelin fraction is selectively enriched in those mRNAs. The four major myelin basic protein (MBP) mRNAs that arise by alternative splicing of exons II and VI of the MBP gene are concentrated in this subcellular fraction. Furthermore, an interaction of MBP and MOBP 81A mRNAs with the cytoskeleton was observed. This interaction might serve to mediate the anchoring of these messengers after translocation to the subcellular site of translation.
Insights
Messenger RNA (mRNA) localization directs protein synthesis in cells. This study shows myelin basic protein (MBP) mRNAs are concentrated in myelin fractions within oligodendrocytes, interacting with the cytoskeleton for targeted translation.
Area of Science:
- Cell biology
- Neuroscience
- Molecular biology
Background:
- mRNA sorting directs protein synthesis to specific cellular locations.
- In the central nervous system, myelin-specific mRNAs are found in oligodendrocyte processes.
Purpose of the Study:
- To investigate the subcellular localization of myelin basic protein (MBP) mRNAs.
- To determine if MBP mRNAs interact with the cytoskeleton in oligodendrocytes.
Main Methods:
- Biochemical and subcellular fractionation techniques.
- In situ hybridization analysis (previously reported).
Main Results:
- A myelin fraction was selectively enriched in MBP mRNAs.
- Four major MBP mRNA variants, arising from alternative splicing, were concentrated in this fraction.
- An interaction between MBP and MOBP 81A mRNAs and the cytoskeleton was observed.
Conclusions:
- MBP mRNAs are specifically localized to myelin fractions in oligodendrocytes.
- Cytoskeletal interaction may anchor these mRNAs at their translation sites.