Nucleotide sequence determining the first cleavage site in the processing of mouse precursor rRNA

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Ribosomal RNA (rRNA) processing is a fundamental cellular process.
• The initial step in 47S precursor rRNA processing involves endonucleolytic cleavage and fragment degradation.
• Sequence conservation between mouse and human rRNA suggests functional importance.

Purpose of the Study:

• To investigate the role of conserved sequences in rRNA processing.
• To identify the specific regions responsible for endonucleolytic cleavage and fragment degradation.

Main Methods:

• In vitro transcription of deletion mutants of mouse rDNA.
• Analysis of rRNA processing efficiency using S-100 transcription reactions.
• Systematic deletion analysis approaching the processing region from 5' and 3' directions.

Main Results:

• A sharp 5' boundary for processing was identified at the rRNA cleavage site.
• 3' deletions significantly impacted processing efficiency, with deletions beyond 91 nucleotides virtually eliminating it.
• Altered ionic conditions allowed low-level processing with 3' deletions extending to 41 nucleotides.

Conclusions:

• The conserved sequence 3' to the primary rRNA processing site contains multiple domains.
• These domains are essential for directing endonucleolytic cleavage and selective degradation of the upstream fragment.
• This highlights the intricate regulation of rRNA maturation.