Processing of ribosomal precursor RNAs in Physarum polycephalum

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Ribosomal RNA (rRNA) synthesis and processing are fundamental cellular processes.
• Understanding rRNA gene organization and transcription is crucial for cell biology.

Purpose of the Study:

• To investigate the processing of Physarum rRNA intermediates.
• To characterize the transcription start and stop sites of rRNA synthesis.
• To determine the role and removal order of introns in rRNA maturation.

Main Methods:

• Utilized cloned rDNA restriction fragments as sequence-specific probes.
• Employed denaturing gel electrophoresis to determine RNA sizes.
• Performed R-loop analysis to map intron-containing transcripts and gene locations.

Main Results:

• Identified the largest stable pre-rRNA at 11.8 Kb.
• Found that most pre-rRNA lacks the two insertion sequences (introns) in the 26 S gene.
• Observed that introns are transcribed and spliced out in a random order.
• Determined transcription starts at ~17.7 Kb and stops at ~4.4 Kb.
• Located the 5.8 S RNA genes using R-loop mapping.

Conclusions:

• Physarum rRNA introns are transcribed and spliced out randomly before transcription termination.
• The processing pathway involves a large precursor RNA that undergoes sequential or random intron removal.
• This study elucidates key aspects of rRNA gene expression and processing in Physarum.