The Role of Ribosomal Proteins eL15 and eL36 in the Early Steps of Yeast 60S Ribosomal Subunit Assembly

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Ribosomal proteins are essential for ribosome structure, function, and biogenesis.
• Previous studies in Saccharomyces cerevisiae have analyzed most, but not all, ribosomal proteins in ribosome synthesis.

Purpose of the Study:

• To characterize the role of yeast ribosomal protein eL15 in the formation of the 60S ribosomal subunit.
• To investigate the impact of eL15 depletion on pre-rRNA processing, nucleocytoplasmic export, and the assembly of early pre-60S particles.

Main Methods:

• In vivo depletion of eL15 in Saccharomyces cerevisiae.
• Analysis of pre-rRNA processing intermediates (27SA3, 27SB, 25S, 5.8S rRNAs).
• Assessment of pre-60S particle nucleocytoplasmic export.
• Analysis of the composition of early pre-60S particles upon depletion of eL15 or eL36.

Main Results:

• Depletion of eL15 leads to a shortage of 60S subunits and half-mer polysomes.
• Defective processing of 27SA3 to 27SB pre-rRNA and subsequent maturation of 25S and 5.8S rRNAs.
• Impaired nucleocytoplasmic export of pre-60S particles.
• Co-depletion of eL15 and eL36 affects their mutual assembly and that of neighboring proteins like eL8.
• Absence of key ribosome assembly factors (A3- and B-factors) in eL15/eL36-depleted intermediates.

Conclusions:

• eL15 is essential for 60S ribosomal subunit biogenesis, affecting rRNA processing and export.
• Assembly of eL15, eL8, and eL36 is critical for shaping domain I of 5.8S/25S rRNA in early pre-60S particles.
• These proteins recruit specific assembly factors necessary for rRNA maturation.