LAS1L interacts with the mammalian Rix1 complex to regulate ribosome biogenesis
Christopher D Castle1, Erica K Cassimere, Catherine Denicourt
1Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, TX 77030, USA.
Molecular Biology of the Cell
|December 23, 2011
Summary
Researchers identified a new protein complex in the nucleolus involving LAS1L, crucial for synthesizing the 60S ribosomal subunit. This complex is essential for ribosome biogenesis and cell cycle progression in mammals.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Ribosome biogenesis is a complex, highly regulated process involving RNA polymerase I transcription, pre-rRNA processing, and subunit assembly.
- Accessory factors coordinate these steps, but their precise functions and assembly into subcomplexes are not fully understood.
- LAS1L (NOL10) was previously known as a nucleolar protein involved in 60S preribosomal subunit maturation.
Purpose of the Study:
- To identify and characterize novel protein complexes involved in ribosome biogenesis.
- To elucidate the function of LAS1L and its interacting partners in the nucleolus.
- To understand the regulation of the 60S ribosomal subunit synthesis.
Main Methods:
- Co-immunoprecipitation to identify interacting proteins.
- Cellular fractionation and co-fractionation studies.
- RNA interference (RNAi) for protein depletion and analysis of cellular phenotypes (cell cycle arrest, pre-rRNA processing).
- Assessment of nucleolar localization and dependence on RNA polymerase I transcription and SENP3 activity.
Main Results:
- LAS1L forms a novel nucleolar complex with PELP1, TEX10, WDR18, NOL9, and SENP3, which cofractionates with the 60S preribosomal subunit.
- Depletion of LAS1L-associated proteins induces a p53-dependent G1 cell cycle arrest.
- Defects in the processing of the internal transcribed spacer 2 (ITS2) region of pre-rRNA were observed upon depletion of these proteins.
- The complex's nucleolar localization depends on active RNA polymerase I transcription and SENP3 activity.
Conclusions:
- A novel mammalian nucleolar complex, including LAS1L, PELP1, TEX10, WDR18, NOL9, and SENP3, is identified and characterized.
- This complex plays a critical role in the maturation of the 60S ribosomal subunit and pre-rRNA processing.
- The findings provide new insights into the intricate process of ribosome biogenesis in higher eukaryotes and its regulation.
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