Revisiting the operational RNA code for amino acids: Ensemble attributes and their implications.

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Bioinformatics

Background:

• The tRNA acceptor stem is proposed to encode amino acids via an operational RNA code.
• Previous research has identified attributes of this code in limited model organisms.
• Understanding the broader code attributes requires analyzing diverse species.

Purpose of the Study:

• To investigate the ensemble attributes of the operational RNA code across bacterial and archaeal species.
• To compare the degeneracy and specificity of the RNA code with the genetic code.
• To explore taxon-specific variations and ambiguities within the RNA code.

Main Methods:

• Analysis of 4925 transfer RNA (tRNA) sequences from 102 bacterial and 21 archaeal species.
• Application of Classification and Regression Trees (CART) methodology.
• Partitioning data by aminoacyl-tRNA synthetase class.

Main Results:

• The RNA codes in Archaea and Bacteria exhibit different degrees of degeneracy and specificity compared to the genetic code.
• Identified taxon-specific alternative codes and instances of code ambiguity within species.
• Partitioning by synthetase class significantly reduced code ambiguity.

Conclusions:

• Synthetase class distinctions are key to resolving RNA code ambiguities, acting as decryption rules.
• Findings support the hypothesis that tRNA acceptor stem-synthetase interactions shaped early enzyme class distinctions.
• Ambiguities in the ancient RNA code were critical for the evolution and fixation of synthetases in prokaryotes.