Information Gradient among Nucleotide Sequences of Essential RNAs from an Evolutionary Perspective

Area of Science:

• Origin of Life studies
• Molecular Evolution
• Genomics

Background:

• The transition from non-living organic molecules to the first protocells marks a critical juncture in life's history.
• The earliest molecular structures, including RNA and peptides, are hypothesized to have laid the groundwork for extant cellular life.
• Traces of these primordial molecules may persist within the genetic material of contemporary organisms.

Purpose of the Study:

• To investigate the hypothesis that ancestral RNA structures left detectable imprints in modern cellular RNAs.
• To propose a circular RNA model as a potential ancestral structure.
• To identify vestigial pentameric subsequences in current RNAs as markers of early evolution.

Main Methods:

• Analyzing nucleotide sequences of modern RNAs (ribosomal and messenger).
• Searching for specific pentameric (or longer) fragments indicative of a proposed primitive RNA structure.
• Quantifying the occurrence frequency of these fragments across different cellular functions and species.

Main Results:

• A gradient in the occurrence frequency of identified pentamers was observed.
• Pentamers were found at higher frequencies in RNAs associated with vital cellular processes, such as protein synthesis, nucleic acid synthesis, and cellular respiration.
• This frequency gradient was also evident across species, correlating with evolutionary age, from Archaea to Eukaryotes.

Conclusions:

• The study provides evidence supporting the hypothesis that ancient RNA structures have left molecular traces in present-day cellular RNAs.
• The identified pentameric subsequences and their occurrence gradients suggest a link to the evolution of fundamental cellular processes and species.
• These findings offer insights into the early stages of life's evolution and the transition from protocells to living organisms.