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A Bioinformatics Pipeline for Investigating Molecular Evolution and Gene Expression using RNA-seq
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Streamlining tRNA-Synthetase Evolution for Genetic Code Expansion and Deep Sequencing Analyses of Its Evolved

Michael Shaferman, Itay Moshel, Shiran Dror

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    PubMed
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    This study simplifies directed evolution to enhance pyrrolysyl-tRNA synthetase (PylRS) activity for genetic code expansion. The accessible method improves noncanonical amino acid incorporation, crucial for protein engineering.

    Keywords:
    PylRSgenetic code expansionnegative selectionpositive selectiontRNA-synthetase directed evolutiontandem mutations

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    Area of Science:

    • Synthetic Biology
    • Protein Engineering
    • Biochemistry

    Background:

    • Genetic code expansion (GCE) enables incorporating noncanonical amino acids (ncAAs) into proteins using orthogonal tRNA and aminoacyl-tRNA-synthetase (aaRS) pairs.
    • While GCE offers diverse applications like labeling and cross-linking, enhancing ncAA incorporation efficiency remains a key challenge.
    • Directed evolution is a powerful strategy to improve aaRS activity by introducing and selecting for beneficial mutations.

    Purpose of the Study:

    • To develop and present a simplified, accessible directed evolution system for improving the activity of pyrrolysyl-tRNA synthetase (PylRS) from *Methanosarcina mazei*.
    • To evolve PylRS variants for enhanced incorporation of specific noncanonical amino acids.
    • To investigate the effectiveness of tandem codon randomization in improving PylRS function.

    Main Methods:

    • Implemented a simplified directed evolution system using basic laboratory equipment.
    • Evolved PylRS variants against three distinct substrates, generating substrate-specific mutations.
    • Utilized deep sequencing to analyze mutations, assess PylRS activity and expression, and validate the evolutionary strategy.

    Main Results:

    • Successfully evolved PylRS variants with improved activity towards specific substrates.
    • Identified unique, substrate-specific mutations through directed evolution pathways.
    • Demonstrated that tandem codon randomization effectively enhances PylRS function through additive mutation effects.
    • Deep sequencing confirmed the efficiency of the approach and highlighted the benefits of tandem mutations.

    Conclusions:

    • The presented simplified directed evolution system effectively streamlines the process of evolving PylRS.
    • The findings provide valuable insights into strategies for enhancing ncAA incorporation efficiency.
    • This work facilitates advancements in synthetic biology and protein engineering applications requiring improved GCE.