In vivo characterization of yeast mRNA processing intermediates

Area of Science:

• Molecular Biology
• RNA Splicing
• Yeast Genetics

Background:

• Yeast mRNA introns possess a conserved TACTAAC sequence crucial for splicing.
• Previous studies identified a reverse transcriptase stop at the TACTAAC box in wild-type rp51A intron splicing intermediates.

Purpose of the Study:

• To investigate the nature of the reverse transcriptase stop at the TACTAAC box in yeast mRNA splicing.
• To characterize the composition and structure of putative splicing intermediates.
• To compare early steps in yeast and mammalian mRNA splicing.

Main Methods:

• Reverse transcriptase stop analysis at the TACTAAC box of yeast introns (rp51A and actin).
• RNA characterization of splicing intermediates, including lariat formation and exon composition.

Main Results:

• The reverse transcriptase stop occurs at the branch nucleotide within the TACTAAC box of both wild-type rp51A and actin introns.
• A key intermediate was identified containing a complete intron and the 3' exon, lacking the 5' exon, and existing primarily as a lariat structure.
• Other intermediates, including excised intron forms and free 5' exon, were detected.

Conclusions:

• The formation of a lariat structure and the cut at the 5' junction represent early events in yeast mRNA splicing.
• Significant similarities exist between the mRNA splicing mechanisms in yeast and mammals.