Heterochromatin aggregation during DNA elimination in Tetrahymena is facilitated by a prion-like protein

Abstract

Regulated aggregations of prion and prion-like proteins play physiological roles in various biological processes. However, their structural roles in the nucleus are poorly understood. Here, we show that the prion-like protein Jub6p is involved in the regulation of chromatin structure in the ciliated protozoan Tetrahymena thermophila. Jub6p forms sodium dodecyl sulfate (SDS)-resistant aggregates when it is ectopically expressed in vegetative cells and binds to RNA in vitro. Jub6p is a heterochromatin component and is important for the formation of heterochromatin bodies during the process of programmed DNA elimination. We suggest that RNAprotein aggregates formed by Jub6p are an essential architectural component for the assembly of heterochromatin bodies.

Discovering Putative Prion-Like Proteins in Plasmodium falciparum: A Computational and Experimental Analysis

“…At this point, to dig a bit more on the functional role of our protein subset, we reanalyzed the MF category setting a p -value cutoff of 0.1. Several new GO terms came to light that could be grouped into two interesting MF subclusters: (i) chromatin remodeling, which is consistent with recent studies demonstrating that the physical properties of PrLDs can retarget critical chromatin regulatory complexes ( Boulay et al, 2017 ) and facilitate heterochromatin assembly ( Kataoka and Mochizuki, 2017 ) and (ii) GTPase regulatory activity, which is also detected in the PrLD-containing proteins of several other organisms (bacteria, plants, fungi, and invertebrates) ( Espinosa Angarica et al, 2013 ); indeed, the canonical and best characterized yeast prion, Sup35, is a GTPase ( Glover et al, 1997 ).…”

Roles of Noncoding RNAs in Ciliate Genome Architecture

“…Heterochromatin body formation is dependent on the dephosphorylation of Pdd1, which is hyperphosphorylated on heterochromatin formation [ 50 , 51 ]. As yet, it is unclear whether the heterochromatin body formation occurs before or after excision of the IESs and TEs has begun; however, it seems to be necessary for excision as knockout of proteins involved in heterochromatin body formation leads to retention of IESs in the daughter macronucleus [ [52] , [53] , [54] , [55] , [56] ]. Interestingly, one of these proteins is an RNA-binding protein that forms prion-like aggregates, suggesting that RNA may be involved in the aggregation of heterochromatin into foci [ 56 ].…”

Non-coding RNA Transcription in Tetrahymena Meiotic Nuclei Requires Dedicated Mediator Complex-Associated Proteins

“…Emit1, Emit2, and Rib1 Colocalize with Pol II and Med in the Meiotic MIC To investigate the spatial relationships between Med-associated proteins and the transcriptional machinery, we first determined Pol II and Med localization in WT cells. Pol II localization was determined by immunostaining with an antibody against Rpb3, a Tetrahymena Pol II subunit [33], and Med localization was determined with immunostaining for HA-tagged Med31, a conserved Med subunit [32]. Rpb3 and Med31 were constitutively localized in the MAC ( Figure 4A).…”

“…mCherry-tagged MicNup98A was detected with rabbit anti-dsRed polyclonal antibody (1:100 dilution; Clontech Laboratories, Mountain View, CA, USA). Rpb3 was detected with a custom rabbit anti-Tetrahymena Rpb3 polyclonal antibody (1:100 dilution) [33]. Dmc1 and Rad51 were stained with mouse anti-Rad51/Dmc1 monoclonal antibody (1:50 dilution; Lab Vision, Fremont, CA, USA).…”