Differentiated cytoplasmic granule formation in quiescent and non-quiescent cells upon chronological aging

Abstract

Stationary phase cultures represent a complicated cell population comprising at least two different cell types, quiescent (Q) and non-quiescent (NQ) cells. Q and NQ cells have different lifespans and cell physiologies. However, less is known about the organization of cytosolic protein structures in these two cell types. In this study, we examined Q and NQ cells for the formation of several stationary phase-prevalent granule structures including actin bodies, proteasome storage granules, stress granules, P-bodies, the compartment for unconventional protein secretion (CUPS), and Hsp42-associated stationary phase granules (Hsp42-SPGs). Most of these structures preferentially form in NQ cells, except for Hsp42-SPGs, which are enriched in Q cells. When nutrients are provided, NQ cells enter mitosis less efficiently than Q cells, likely due to the time requirement for reorganizing some granule structures. We observed that heat shock-induced misfolded proteins often colocalize to Hsp42-SPGs, and Q cells clear these protein aggregates more efficiently, suggesting that Hsp42-SPGs may play an important role in the stress resistance of Q cells. Finally, we show that the cell fate of NQ cells is largely irreversible even if they are allowed to reenter mitosis. Our results reveal that the formation of different granule structures may represent the early stage of cell type differentiation in yeast stationary phase cultures.

Gearing up for survival – HSP-containing granules accumulate in quiescent cells and promote survival

“…Lee et al . also proved that the Q cells reenter the mitotic cycle more quickly after nutrition replenishment 5, which further establishes the phenotypical difference between the two cell types (Fig. 1).…”

“…In this issue, Lee et al . reports that distinct granules are formed in Q and NQ cells, which determines their respective cell fates 5. The authors asked whether different kinds of granules were distributed uniformly between Q and NQ cells, and found that most granule structures are enriched in NQ cells with the exception of Hsp42-associated stationary phase granules (Hsp42-SPGs) (Fig.…”

Experimental evolution reveals a general role for the methyltransferase Hmt1 in noise buffering

“…The other part was placed in fresh YPD media for 2.5 h and then subjected to the same heat treatment. Cell survival rates were measured as colony-forming units after 3 days of incubation at 28 C.As a rebudding assay, more than 100 unsorted stationary-phase cells were placed on agarose pads and monitored by time-lapse microscopy at 15 min intervals for at least 12 h[82]. Only unbudded cells at the beginning of the recording period were monitored.…”

Density Separation of Quiescent Yeast Using Iodixanol

“…Unlike dividing cells, Q cells are thermotolerant (5) and possess cell walls resistant to zymolyase (6). NQ cells, on the contrary, are less resistant to these treatments and are prone to genomic instability (5,7,8).…”

“…Unlike dividing cells, Q cells are thermotolerant (5) and possess cell walls resistant to zymolyase (6). NQ cells, on the contrary, are less resistant to these treatments and are prone to genomic instability (5,7,8). Because of their short life cycle and the extensive availability of molecular tools, budding yeast are an excellent model in which to study the unique biology of quiescence (9).…”