For example, recursive splicing must now be taken into account when evaluating mutations that disrupt gene expression and produce a dysfunctional or non-functional protein.
"Current data indicate that at least 15 percent of disease-causing mutations occur at standard signals where intron removal takes place through direct splicing. Mutations at recursive splice sites may cause additional diseases, but until now we haven't looked for them."
Knowledge of recursive splicing also will help investigators predict structures of genes that span large intervals of DNA, Lopez said.
Recursive splicing relies on the unusual activity of a ratchetting point, a pattern of chemical groups (nucleotides) previously discovered within the genome by Lopez. One end of a ratchetting point contains a sequence of nucleotides similar to the signal normally found at the beginning of an intron. This signal is juxtaposed with another sequence like that normally found at the end of an intron. Such a unique pairing allows a ratchetting point to function sequentially as an acceptor for splicing to an upstream exon and then as a donor for splicing to the next downstream ratchetting point or exon. As the process goes from ratchetting point to ratchetting point, small signature loops of RNA called lariats are released from the intron. Repeated over and over, recursive splicing eventually binds, or ligates, two distant exons.
Lopez's team developed molecular tools to analyze the lariats released from any intron during splicing in vivo. In his analyses, he found that the production of recursive lariats greatly exceeded that of direct lariats, indicating that recursive splicing is the predominant processing pathway for long introns. Lopez combined these experimental data with computational and phylogenetic analyses of several fruitfly and oth
Source:Carnegie Mellon University