Towards a Shape Language for Interpreting RNA Folding

In this paper we introduce a shape language for representing RNA secondary structures in a non-standard, non-linear way. The main motivation is to propose a new interpretation of RNA folding as a self-adaptability process, within the S[B] paradigm, towards a minimum free energy configuration. An RNA secondary structure is decomposed first by distinguishing between pseudoknot free and pseudonotted sub-structures. For pseudoknot free sub-structures a proper formal language is defined. To address the representation of pseudoknotted sub-structures the crucial aspects of RNA irreducible shapes and their associated automatic groups are introduced.