Nop53p is required for late 60S ribosome subunit maturation and nuclear export in yeast

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Ribosome biogenesis is a complex process involving the coordinated synthesis of ribosomal RNA (rRNA) and ribosomal proteins.
• The 60S ribosomal subunit is essential for protein synthesis and undergoes extensive processing and assembly within the nucleus.
• Nuclear export of functional ribosomal subunits is a critical step for cellular function.

Purpose of the Study:

• To investigate the role of Ypl146cp/Nop53p in the biogenesis and nuclear maturation of the 60S ribosomal subunit.
• To determine the localization and function of Nop53p within the ribosome assembly pathway.
• To understand the impact of Nop53p depletion on rRNA processing and subunit export.

Main Methods:

• Localization studies using microscopy to determine Nop53p cellular localization.
• Analysis of rRNA processing intermediates and mature rRNA in Nop53p-depleted cells.
• Heterokaryon assays to assess Nop53p nuclear-cytoplasmic transport.
• Analysis of pre-60S ribosomal subunit accumulation in Nop53p-deficient strains.

Main Results:

• Nop53p localizes to the nucleolus and nucleoplasm and associates with pre-60S ribosomal complexes.
• Depletion of Nop53p severely inhibits 60S ribosomal subunit rRNA synthesis, leading to accumulation of 7S pre-rRNA and a 5' extended 25S rRNA.
• Pre-60S subunits accumulate in the nucleus of Nop53p-depleted cells, and Nop53p is not transferred between nuclei.
• Aberrant preribosomes accumulate in Nop53p-depleted cells, suggesting a role in surveillance pathways.

Conclusions:

• Nop53p functions as a late-acting factor in the nuclear maturation of 60S ribosomal subunits.
• Nop53p is essential for the acquisition of export competence of 60S ribosomal subunits.
• Nop53p may play a role in targeting aberrant preribosomes for degradation.