Unitary circular code motifs in genomes of eukaryotes

Area of Science:

• Genomics and Bioinformatics
• Molecular Biology
• Computational Biology

Background:

• A set X of 20 trinucleotides exhibits a higher occurrence in the correct reading frame across various organisms.
• This set X functions as a circular code, enabling the retrieval, synchronization, and maintenance of gene reading frames.
• The evolutionary origin of this circular code X remains an open question since its discovery.

Purpose of the Study:

• To investigate the role of unitary circular codes (UCC) and their associated motifs (UCC motifs) in generating low-complexity DNA.
• To analyze the statistical distribution and properties of UCC motifs (repeated dinucleotides, trinucleotides, and tetranucleotides) in eukaryotic genomes.
• To explore the potential evolutionary link between UCC motifs and the formation of the trinucleotide circular code X.

Main Methods:

• Identification and classification of unitary circular code motifs (UCC motifs), including repeated dinucleotides (D+), trinucleotides (T+), and tetranucleotides (T+).
• Statistical analysis of the distribution of these UCC motifs within eukaryotic genomes.
• Comparison of the occurrences and complementary distributions of UCC motifs and their complements.

Main Results:

• UCC motifs (D+, T+, T+) were found to retrieve, synchronize, and maintain reading frames modulo 2, 3, and 4, respectively.
• A scarcity of repeated trinucleotides (T+ motifs) was observed in large eukaryotic genomes compared to D+ and T+ motifs.
• Repeated trinucleotides (T+ motifs) were identified within X motifs of low cardinality, suggesting a potential evolutionary role.

Conclusions:

• Unitary circular codes and their motifs are fundamental in establishing and maintaining reading frames in DNA sequences.
• The observed scarcity of T+ motifs in eukaryotes, coupled with their presence in low-cardinality X motifs, points to an evolutionary transition.
• These findings suggest that unitary circular codes of trinucleotides may have been instrumental in the evolution of the trinucleotide circular code X.