Biology subjects

Rajyaguru, P. I.

Publications and source records attributed to Rajyaguru, P. I..

9 recordsLinked to original sources

bioRxiv2026

PRMT1/Hmt1 drives α-synuclein aggregate dissolution through a catalysis-independent pathway

Protein homeostasis, the balance between protein folding, function, and clearance, is essential for cellular health, and its disruption is a hallmark of many neurodegenerative diseases, including Parkinsons disease. Arginine methylation, carried out by enzymes like Hmt1 in yeast and PRMT1 in humans, is best known for regulating transcription, translation, apoptosis and pre-mRNA splicing. In this study, we reveal a surprising, non-canonical role for these methyltransferases in controlling the aggregation and toxicity of -synuclein, a protein lacking arginine and implicated in Parkinsons disease pathology. We find that under oxidative stress, Hmt1 and PRMT1 relocate from the nucleus into the cytoplasm. Using genetic, biochemical and imaging assays in yeast and mammalian cells, we observe that Hmt1/PRMT1 dissolve aggregates, promotes their removal through the ubiquitin-proteasome system, and reduces -synuclein toxicity. Importantly, this activity does not require the classical methyltransferase function. Catalytically inactive mutants and a specific PRMT1 inhibitor both enhance aggregate clearance and improve cell survival. Together, our findings uncover an unexpected function for Hmt1 and PRMT1 in maintaining protein quality under stress, expanding our understanding of how cells cope with toxic protein assemblies and pointing to new directions for therapeutic strategies in protein aggregation disorders.

biochemistry↗

bioRxiv2026

DDX3X syndrome mutations lock DDX3X-RNA conformational states to drive persistent pathological condensation and neuronal death

DDX3X is a highly conserved RNA helicase associated with RNA metabolism, translation initiation, and deciding cell fate choices. Spontaneous mutations in DDX3X cause a rare genetic human disorder called DDX3X syndrome, showing a spectrum of neurodevelopmental and intellectual abnormalities. How missense mutations in DDX3X lead to aberrant cellular functions and pathological consequences is unclear. Here, we demonstrate that specific DDX3X syndrome missense mutations induce the formation of persistent, solid-like DDX3X stress granules by structurally altering the conformation of the DDX3X-RNA complex. Structural interrogation of DDX3X syndrome missense mutations revealed critical mutations that perturb the DDX3X-RNA complex, exhibit high clinical pathogenicity scores, and are associated with cancers. N and C-terminal mutations adjacent to the helicase domain of the DDX3X (F182V, I190S, T198P, L556S, and L559H) showed augmented stress granule (SG) assembly, and formation of persistent DDX3X-SGs in neuronal and non-neuronal cells. Intriguingly, these mutations altered the liquid-like properties of DDX3X-SGs, forming solid-like SGs. Mechanistically, these mutations drive the persistent DDX3X-SGs by either locking DDX3X in an open, RNA-bound conformation or by increasing the rigidity of the DDX3X-RNA complex (I190S; T198P), thereby conferring a loss of liquid-like properties. The persistent solid-like DDX3X-SGs preferentially promoted neuronal lytic cell death and did not affect translation. Also, the C-terminal L556S and L559H mutations, which form persistent granules, promoted the DDX3X-driven {beta}-amyloid aggregation. Our observations indicate that DDX3X syndrome mutations near the N- and C-termini promote the formation of solid-like DDX3X condensates, neuropathological aggregation, and neuronal cell death, which might underlie the disease pathogenesis in humans. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/702492v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@164b436org.highwire.dtl.DTLVardef@73741aorg.highwire.dtl.DTLVardef@1cb6fcforg.highwire.dtl.DTLVardef@119b652_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Ribonucleoprotein (RNP) condensates modulate survival in response to Mars-like stress conditions

Scientific advances have emboldened human efforts toward exploring the potential of extinct, extant, or future life on Mars. An important aspect of this endeavor is understanding how an organism adapts to stress-inducing environmental conditions on Mars, such as radiation, shock waves, extreme temperatures, and chaotropic stress due to higher levels of perchlorates. A conserved approach used by organisms across evolutionary scales to adapt and overcome stress conditions is the assembly of ribonucleoprotein (RNP) condensates. In this study, we employ a multidisciplinary approach to understand yeast survivability and adaptation under Mars-like stress conditions, specifically shock waves and perchlorate, by focusing on RNP condensates. Our study reveals that yeast survives 5.6 M intensity shock waves. Exposure to either shock waves or sodium perchlorate induces the formation of P-bodies, a conserved stress-induced condensate. Yeast mutants defective in P-body assembly show defective growth in response to perchlorate stress. Transcriptome analysis, followed by validation, identified several relevant transcripts whose levels are perturbed in response to Mars-like conditions. Finally, identification of several transcripts whose abundance is altered in the P-body assembly mutant upon stress highlights a new connection between response to Martian stress conditions and RNP condensates. This study, a first of its kind, highlights the importance of RNP condensates in understanding the impact of Martian conditions on life in general. This study paves the way for using RNP condensates as a biomarker for assessing the health of life forms during space explorations.

cell biology↗

bioRxiv2025

Translation control of autophagy genes upon hydroxyurea-induced genotoxic stress

The fine balance between cellular homeostasis and stress response is crucial for cell survival. In this study, we identify translation regulation of specific autophagy (ATGs) genes by translation repressor Sbp1 upon hydroxyurea-mediated genotoxic stress. Sbp1 localizes to reversible, mRNA-containing granules specifically upon HU stress in RNA recognition motif 1 (RRM1) and RGG motif-dependent manner. Granule localization is independent of eIF4G1 binding despite increased arginine methylation. Deletion of SBP1 increased the tolerance to HU. RNA sequencing of polysome fractions identified ATG1, 2, 9 mRNAs being translationally upregulated in{Delta} sbp1 upon HU stress. Translation of TEL1 and MEC1, the upstream activators of autophagy, also increased in{Delta} sbp1. Concomitantly, increased autophagy and decreased NHEJ repair in{Delta} sbp1 cells was observed. Together, these findings identify Sbp1 as a regulator of the autophagy pathway in response to genotoxic stress by modulating autophagy at two levels, possibly mediated by its ability to localize to granules.

cell biology↗

bioRxiv2025

RGG peptide induces the disassembly of disease-relevant FUS and TDP43 condensates

Mislocalization and cytoplasmic condensation of nuclear proteins, such as FUS and TDP43, are key features of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, mechanisms governing the disassembly of these pathological condensates remain elusive. Here, we identify a disordered RGG peptide as a disassembly factor for mutant FUS and TDP43 condensates. Using yeast, mammalian cells, and in vitro assays, we observe that an RGG motif reduces condensate burden and toxicity while restoring nuclear localization and RNA regulatory defects associated with the FUS-P525L mutant. The RGG motif interacts with FUS, competitively inhibiting FUS self-association. Overall, our findings uncover a direct role for a disordered RGG motif in the disassembly of ALS-associated condensates, highlighting the possibility of a new therapeutic for post-symptomatic ALS.

cell biology↗

bioRxiv2023

RGG-motif protein Scd6 affects oxidative stress response by regulating Cytosolic caTalase T1 (Ctt1)

In response to stress, cells undergo gene expression reprogramming to cope with external stimuli. As translation is energy consuming process, its regulation during stress is crucial for cellular adaptation. Cells utilize a conserved stress response mechanism called global downregulation of translation, leading to the storage of translationally repressed mRNAs in RNA granules or RNP condensates. During oxidative stress induced by H2O2, genes responsible for combating oxidative stress, such as catalases and glutathione peroxidase, are strongly induced. However, the post-transcriptional regulatory events affecting these genes during H2O2 stress are not well-explored. RNA binding proteins such as RGG motif proteins play a critical role in mediating translation regulation and have diverse physiological functions. Scd6, an RGG motif-containing protein in yeast, acts as a translational repressor through its interaction with eIF4G. Although the role of Scd6 as a translational repressor and decapping activator is known, its specific mRNA targets are largely unknown.This study identifies the role of Scd6 in oxidative stress response by regulating cytoplasmic catalaseT1 (CTT1). Altering Scd6 levels influenced Ctt1 protein levels, thereby affecting oxidative stress response. Scd6 overexpression increased sensitivity, while deletion enhanced tolerance to H2O2 treatment due to ROS accumulation in the yeast cell. In response to H2O2 treatment, Scd6 forms dynamic puncta which contains RNA. Overall, this study proposes regulation of oxidative stress response via modulation of CTT1 mRNA by Scd6.

molecular biology↗

bioRxiv2022

RGG-motif proteins regulate mRNA translation upon genotoxic stress

Genotoxic stress response (GSR) mediated by mRNA translation and decay regulation remains poorly explored. Here, we identify a unique role of yeast RGG-motif protein Scd6 and its human ortholog LSM14A in mRNA translation control upon hydroxyurea (HU)-mediated GSR. Scd6/LSM14A, but not all tested RGG-containing proteins, localize to HU-induced cytoplasmic puncta in an RGG-dependent manner. The absence of Scd6 increases HU tolerance but sensitizes the cells to HU upon overexpression of SRS2, a known dampener of the DNA- damage response. Scd6 binds SRS2 mRNA to repress its translation in cytoplasmic granules upon HU stress. Scd6-SRS2 interaction is modulated by arginine methylation (AM) and the LSm-domain, which acts as a cis-regulator of Scd6 AM. Polysome-profiling experiments indicate that LSM14A regulates the translation of NHEJ factor mRNAs such as LIG4 (DNL4 homolog) and RTEL1 (SRS2 functional homolog), and the NHEJ activity in response to HU. Overall, this report unveils the role of AM and Scd6/LSM14A in the GSR by determining the translation status of specific mRNAs.

cell biology↗

bioRxiv2021

RGG-motif protein Sbp1 is required for Processing body (P-body) disassembly

RNA granules are conserved mRNP complexes that play an important role in determining mRNA fate by affecting translation repression and mRNA decay. Processing bodies (P-bodies) harbor enzymes responsible for mRNA decay and proteins involved in modulating translation. Although many proteins have been identified to play a role in P-body assembly, a bonafide disassembly factor remains unknown. In this report, we identify RGG-motif translation repressor protein Sbp1 as a disassembly factor of P-bodies. Disassembly of Edc3 granules but not the Pab1 granules (a conserved stress granule marker) that arise upon sodium azide and glucose deprivation stress are defective in{Delta} sbp1. Disassembly of other P-body proteins such as Dhh1 and Scd6 is also defective in{Delta} sbp1. Complementation experiments suggest that the wild type Sbp1 but not an RGG-motif deletion mutant rescues the Edc3 granule disassembly defect in{Delta} sbp1. We observe that purified Edc3 forms assemblies, which is promoted by the presence of RNA and NADH. Strikingly, addition of purified Sbp1 leads to significantly decreased Edc3 assemblies. Although low complexity sequences have been in general implicated in assembly, our results reveal the role of RGG-motif (a low-complexity sequence) in the disassembly of P-bodies.

cell biology↗

bioRxiv2020

PSP2, a gene encoding RGG-motif protein, is a novel suppressor of clathrin heavy chain deficiency

Clathrin, made up of the heavy- and light-chains, constitutes one of the most abundant protein in vesicles involved in intracellular protein trafficking and endocytosis. YPR129W, which encodes RGG-motif containing translation repressor was identified as a part of multi-gene construct (SCD6) that suppressed clathrin deficiency. However, the contribution of YPR129W alone in suppressing clathrin deficiency has not been documented. In this study we identify YPR129W as a necessary and sufficient gene in a multigene construct SCD6 that suppresses clathrin deficiency. Importantly, we identify cytoplasmic RGG-motif protein encoding gene PSP2 as a novel suppressor of clathrin deficiency. Three other RGG-motif protein encoding genes SBP1, DED1 and GBP2 do not suppress clathrin deficiency. DHH1, a DEAD-box RNA helicase with translation repression activity also fails to rescue clathrin deficiency. -factor secretion assay suggests that suppression of clathrin deficiency by SCD6 and PSP2 is not mediated by the rescue of the trans-Golgi network (TGN) protein sorting defect observed in the absence of CHC1. Detailed domain analysis of the two suppressors reveals that the RGG-motif of both Scd6 and Psp2 is important for suppressing clathrin deficiency. Additionally, the Lsm domain deletion as well as the arginine to alanine mutation in the arginine methylation defective (AMD) mutant render Scd6 defective in suppressing clathrin deficiency. Overall based on our results using SCD6 and PSP2 proteins, we identify a novel role of RGG-motif in suppressing clathrin deficiency. Since both the suppressors are RNA-binding granule-resident proteins, this study opens an exciting avenue for exploring the connection between clathrin function and cytoplasmic RNA metabolism.

cell biology↗