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DNA sequence and transcript mapping of MOD5: features of the 5' region which suggest two translational starts

D Najarian, M E Dihanich, N C Martin

    Molecular and Cellular Biology
    |January 1, 1987
    PubMed

    Insights

    The yeast MOD5 gene is crucial for synthesizing a modified base in tRNAs across cellular compartments. This gene likely encodes a tRNA-modifying enzyme, with evidence suggesting potential for two protein variants.

    Area of Science:

    • Molecular Biology
    • Yeast Genetics
    • RNA Modification

    Background:

    • The yeast nuclear gene MOD5 plays a critical role in the biosynthesis of isopentenyladenosine, a modified base essential for tRNA function.
    • This modification is vital in tRNAs located in various cellular compartments, including mitochondria, nucleus, and cytoplasm.
    • Evidence strongly implicates MOD5 as the structural gene for the tRNA-modifying enzyme, delta 2-isopentenyl pyrophosphate:tRNA isopentenyl transferase.

    Purpose of the Study:

    • To investigate the molecular function and genetic basis of the MOD5 gene in yeast.
    • To elucidate the role of MOD5 in tRNA modification across different cellular compartments.
    • To analyze the genetic and translational mechanisms associated with the MOD5 gene.

    Main Methods:

    • DNA sequence analysis of the MOD5 gene.
    • Analysis of mRNA transcripts, including 5' and 3' termini heterogeneity.
    • Examination of translation initiation signals, including AUG codon context.

    Main Results:

    • DNA sequencing revealed an open reading frame of 428 amino acids for MOD5.
    • Heterogeneous mRNAs transcribed from MOD5 exhibit variations at 5' and 3' termini.
    • The primary AUG codon is flanked by sequence elements (U at -3, C at +4) potentially influencing translation initiation.

    Conclusions:

    • MOD5 is strongly suggested to be the gene encoding the delta 2-isopentenyl pyrophosphate:tRNA isopentenyl transferase enzyme.
    • The MOD5 gene produces complex mRNA transcripts, indicating sophisticated gene regulation.
    • Differential translational starts from the MOD5 gene may generate two distinct protein products.

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