Physical and coding properties of poly(5-methoxyuridylic) acid

Area of Science:

• Biochemistry
• Molecular Biology
• RNA Synthesis

Background:

• Polynucleotide phosphorylase (PNPase) is crucial for RNA synthesis.
• The secondary structure of synthetic polynucleotides influences their biological activity.
• Ribosome-mediated translation requires specific interactions between mRNA, tRNA, and ribosomal subunits.

Purpose of the Study:

• To synthesize and characterize poly-5-methoxyuridylic acid (poly(mo5U)).
• To investigate the complex formation of poly(mo5U) with poly(A).
• To evaluate the role of poly(mo5U) in ribosome binding and protein synthesis.

Main Methods:

• Enzymatic synthesis of poly(mo5U) using polynucleotide phosphorylase.
• Characterization of poly(mo5U) chain length and secondary structure.
• Formation and thermal denaturation studies of poly(A) . 2poly(mo5U) complex.
• Assays for Phe-tRNA binding to 70-S ribosomes and poly(Phe) synthesis.

Main Results:

• Poly(mo5U) synthesis required high PNPase concentration and long reaction times, yielding short chains (~100 nucleotides) without stable secondary structure.
• A triple-stranded complex, poly(A) . 2poly(mo5U), was formed with a melting temperature of 68.5°C and significant thermal hysteresis (ΔTm = 11.5°C).
• Poly(mo5U) enhanced Phe-tRNA binding to 70-S ribosomes but did not support poly(Phe) synthesis.

Conclusions:

• Poly(mo5U) can form stable triple-stranded complexes with poly(A), exhibiting unique thermal properties.
• Despite stimulating tRNA binding, poly(mo5U) lacks the necessary properties to act as a template for phenylalanine polymerization.
• These findings contribute to understanding the structure-function relationships of synthetic polynucleotides in biological systems.