Title: Significant folding of random sequences

Niels Richard Hansen
Department of Statistics and Operations Research
University of Copenhagen

Abstract:

Small RNA-molecules, many with unknown function, have recently 
been found in great numbers. A class of them baptised
micro-RNA's is believed to regulate the expression of protein coding
genes, and in a pre-functioning state they seem to have a typical 
fold-back structure. It is of great interest to be able to
search entire genomes by computational methods to identify potential
micro-RNA's, and one could look for small segments of the genome 
with a fold-back structure comparable to the known micro-RNA's.

In several empirical studies it has, however, been shown that the
structure of a small RNA-molecule does not distinguish the RNA-sequence
significantly from a random sequence. In the talk, I will show some 
theoretical work on the formation of certain fold-back structures
in random (iid. and Markov) sequences, and for the size and structure 
of typical micro-RNA's, the results confirm earlier studies; that the
fold-back structure alone is not significant for small RNA-molecules.
An idea for searching for small functional RNA-molecules in entire 
genomes based on structure as well as evolutionary conservation in 
two different genomes will also be discussed.