A Hybrid-Body Containing Constituents of Both P-Bodies and Stress Granules Forms in Response to Hypoosmotic Stress in Saccharomyces cerevisiae.

Khyati H Shah,Paul K Herman,Laura A Cook,Sapna N Varia,Michael Polymenis

doi:10.1371/journal.pone.0158776

Abstract

The cytoplasm of the eukaryotic cell is a highly compartmentalized space that contains a variety of ribonucleoprotein (RNP) granules in addition to its complement of membrane-bound organelles. These RNP granules contain specific sets of proteins and mRNAs and form in response to particular environmental and developmental stimuli. Two of the better-characterized of these RNP structures are the stress granule and Processing-body (P-body) that have been conserved from yeast to humans. In this report, we examined the cues regulating stress granule assembly and the relationship between stress granule and P-body foci. These two RNP structures are generally thought to be independent entities in eukaryotic cells. However, we found here that stress granule and P-body proteins were localized to a common or merged granule specifically in response to a hypoosmotic stress. Interestingly, these hybrid-bodies were found to be transient structures that were resolved with time into separate P-body and stress granule foci. In all, these data suggest that the identity of an RNP granule is not absolute and that it can vary depending upon the nature of the induction conditions. Since the activities of a granule are likely influenced by its protein constituency, these observations are consistent with the possibility of RNP granules having distinct functions in different cellular contexts.

Highlights

The distinguishing feature of the eukaryotic cytoplasm is its subdivision into a number of functionally-distinct, membrane-enclosed organelles
Stress granule induction occurs in response to a decrease in osmotic support One of the most common ways to induce stress granules in S. cerevisiae is to transfer cells from a growth medium with glucose to the same medium lacking this sugar (Fig 1A)
These experiments have led to a model proposing that stress granule assembly is triggered by an acute starvation for glucose

Summary

Introduction

The distinguishing feature of the eukaryotic cytoplasm is its subdivision into a number of functionally-distinct, membrane-enclosed organelles. Hybrid-Body Formation in Response to Hypoosmotic Stress membrane but contain distinct sets of proteins and mRNAs at concentrations higher than the surrounding cytoplasm These granules have been found to behave like liquid droplets in the cytoplasm and are thought to form as a result of multivalent interactions occurring between core proteins and mRNAs [1, 4, 5] Two of the best characterized of these structures are the evolutionarily-conserved Processing-body (P-body) and stress granule [6, 7]. Other work has suggested that these foci could represent sites for mRNA storage, miRNA silencing and the regulation of virus production [14,15,16] These suggestions typically arose as a result of experiments identifying novel granule constituents, like the Argonaute proteins [17]. It is important that we define these constituents and the underlying mechanisms governing granule assembly

Methods

Results

Conclusion