Cell-free synthesis of the myelin basic proteins in a wheat germ system programmed with brain messenger RNA

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Messenger RNA (mRNA) isolation and translation are crucial for understanding protein synthesis.
• Myelin basic proteins (MBPs) are essential components of the myelin sheath in the central nervous system.
• Cell-free translation systems offer a controlled environment for studying mRNA-directed protein synthesis.

Purpose of the Study:

• To investigate the cell-free translation of polyadenylated (Poly A(+)) messenger RNA (mRNA) isolated from mouse brains.
• To identify the synthesis of myelin basic proteins (MBPs) using this translational system.
• To characterize the optimal conditions for brain mRNA translation and compare it with liver mRNA.

Main Methods:

• Isolation of Poly A(+) mRNA from the brains of 3-week-old mice.
• Utilizing a wheat germ-derived cell-free translational system.
• Optimizing conditions including K+ concentration, mRNA concentration, energy-generating system, spermidine, and transfer RNA.
• Analyzing translation products using co-chromatography and co-electrophoresis to detect MBP-like polypeptides.
• Comparing translation efficiency and product profiles with Poly A(+) mRNA from mouse liver.

Main Results:

• Maximal stimulation of the cell-free system by brain mRNA occurred at low K+ (45 mM) and mRNA (1-10 microgram/ml) concentrations.
• The translational system required an energy-generating system and was stimulated by spermidine and transfer RNA.
• Despite relatively low overall stimulation (twofold), polypeptides co-migrating with mouse MBPs were detected when using brain mRNA.
• Control experiments with liver mRNA showed greater stimulation but did not produce MBP-like polypeptides.
• The ratio of synthesized small MBP to large MBP was approximately 4.0, consistent with in vivo findings.

Conclusions:

• The cell-free wheat germ system can successfully translate mouse brain mRNA to produce polypeptides resembling myelin basic proteins.
• This system provides a valuable tool for studying MBP synthesis and potentially other brain-specific proteins.
• The observed MBP synthesis ratio in vitro correlates well with in vivo data, validating the system's biological relevance.