Conserved putative signals in 3' intron junctions in rodents

Area of Science:

• Molecular Biology
• Genetics
• RNA Splicing

Background:

• Established 3' splice site signals include an AG doublet and a pyrimidine-rich region.
• Intron splicing involves lariat formation, with a conserved branching point consensus sequence (YNYTRAY).
• The branching point involves a specific adenine residue forming a 2'-5' phosphodiester bond.

Purpose of the Study:

• To identify additional putative regulatory signals surrounding the branching point and 3' splice site in rodent nuclear precursor messenger RNAs (pre-mRNAs).
• To compare identified signals in rodent introns with those found in a broader eukaryotic sample.
• To propose a model for the function of these signals in splicing.

Main Methods:

• Extensive computational searches for conserved sequences in over 370 rodent nuclear pre-mRNA introns.
• Comparison of identified signals with data from over 900 eukaryotic nuclear pre-mRNA introns.
• Development of a structural model to explain the role of identified signals.

Main Results:

• Discovery of two novel putative signals: GGGA (occurring upstream) and CCCA (occurring downstream) of the 3' splice site.
• GGGA was found approximately 60 nucleotides upstream, and CCCA was found 3-40 nucleotides downstream from the 3' splice site.
• These signals were conserved in both rodent and larger eukaryotic intron datasets.

Conclusions:

• GGGA and CCCA represent novel signals potentially involved in regulating pre-mRNA splicing.
• A proposed model suggests these signals may form alternate stem-loop structures.
• These structures could facilitate protein or nucleoprotein recognition of the branching point and 3' splice site.