Journal Article


Nucleolar targeting in an early-branching eukaryote suggests a general mechanism for ribosome protein sorting

Abstract

The compartmentalised eukaryotic cell demands accurate targeting of proteins to the organelles in which they function, whether membrane-bound (like the nucleus) or non-membrane-bound (like the nucleolus). Nucleolar targeting relies on positively charged localisation signals, and has received rejuvenated interest since the widespread recognition of liquid-liquid phase separation (LLPS) as a mechanism contributing to nucleolus formation. Here, we exploit a new genome-wide analysis of protein localisation in an early-branching eukaryote, Trypanosoma brucei, to analyse general nucleolar protein properties. T. brucei nucleolar proteins have similar properties to those in common model eukaryotes, specifically basic amino acids. Using protein truncations and addition of candidate targeting sequences to proteins, we show both homopolymer runs and distributed basic amino acids give nucleolar partition, further aided by a nuclear localisation signal (NLS). These findings are consistent with phase separation models of nucleolar formation and protein physical properties being a major contributing mechanism for eukaryotic nucleolar targeting, conserved from the last eukaryotic common ancestor. Importantly, cytoplasmic ribosome proteins unlike mitochondrial ribosome proteins have more basic residues – pointing to adaptation of physicochemical properties to assist segregation.

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Authors

Jeilani, Milad
Billington, Karen
Sunter, Jack D.
Dean, Samuel
Wheeler, John

Oxford Brookes departments

Department of Biological and Medical Sciences

Dates

Year of publication: 2022
Date of RADAR deposit: 2022-08-25


Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 International License


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This RADAR resource is the Version of Record of [bioRxiv preprint] Nucleolar targeting in an early-branching eukaryote suggests a general mechanism for ribosome protein sorting

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