Biology subjects

Kaypee, S.

Publications and source records attributed to Kaypee, S..

3 recordsLinked to original sources

bioRxiv2026

Excess Met1-ubiquitination leads to solid aggregate formation

The ubiquitin ligase HOIL-1 has a unique role in controlling quantity of Met1-linked/ linear ubiquitin chains in cells by coordinating action with the ubiquitin ligase HOIP. Both ligases are components of the Linear UBiquitin chain Assembly Complex (LUBAC), the only known ligase complex that is able to generate Met1-linked ubiquitin chains. Although importance of Met1-linked ubiquitin chains in inflammation and immunity is well established, physiological relevance of quantity of these chains remain unknown. Here, we demonstrate that cells expressing catalytically inactive HOIL-1 exhibited significantly higher numbers of -Synuclein, tau, and amyloid beta aggregates. This phenotype is associated with a disruption in late-stage autophagic flux, wherein p62-positive aggregates fail to colocalize with lysosomal markers, leading to impaired clearance. Additionally, a biophysical transition in aggregate properties was observed in vitro, with mutant cells forming more rigid solid-like inclusions, shifting from dynamic and liquid-like condensates. Elevated Met1-linked ubiquitin chains, either through HOIL-1 catalytic inactivation or knockdown of the Met1-linked chain-specific deubiquitinase OTULIN, phenocopied the defects in aggregate clearance. These findings reveal a critical role of HOIL-1 catalytic activity in modulating aggregate clearance through autophagy and maintaining the quantity of Met1-ubiquitin chains, highlighting HOIL-1 as a key factor in proteostasis in neurodegenerative diseases. HighlightsO_LIHOIL-1 catalytic activity prevents neurodegenerative protein aggregate accumulation C_LIO_LIInactive HOIL-1 impairs late-stage autophagic clearance of protein aggregates C_LIO_LILoss of HOIL-1 shifts aggregates to rigid, solid-like states C_LIO_LIExcess Met1-ubiquitin chains drive aggregate solidification C_LI

cell biology↗

bioRxiv2018

Deacetylation of catalytic lysine in CDK1 is essential for Cyclin-B binding and cell cycle

Cyclin-dependent-kinases (CDKs) are essential for cell cycle progression. While dependence of CDK activity on Cyclin levels is established, molecular mechanisms that regulate their binding are less studied. Here, we show that CDKl:Cyclin-B interactions are regulated by acetylation, which was hitherto unknown. We demonstrate that cell cycle dependent acetylation of the evolutionarily conserved catalytic lysine in CDK1 or eliminating its charge state abrogates Cyclin-B binding. Opposing activities of SIRT1 and P300 regulate acetylation, which marks a reserved pool of CDK1. Our high resolution structural analyses into the formation of kinase competent CDK1: Cyclin-B complex have unveiled long-range effects of catalytic lysine in configuring the CDK1 interface for Cyclin-B binding. Cells expressing acetylation mimic mutant of Cdc2 in yeast are arrested in G2 and fail to divide. Thus, by illustrating cell cycle dependent deacetylation as a determinant of CDK1:Cyclin-B interaction, our results redefine the current model of CDK1 activation and cell cycle progression.

cell biology↗

bioRxiv2017

Allosteric Activation of p300 Autoacetylation by the Tumor Suppressor p53

The transcriptional coactivator p300 is essential for p53 transactivation, although its precise mechanism remains unclear. We report that, p53 allosterically activates the acetyltransferase activity of p300 through the enhancement of p300 autoacetylation. Cryo-electron microscopy revealed that the domain organization of p300 is substantially altered upon binding of p53, suggesting that a structural switch may underpin the activation. Acetylated p300 accumulates near the transcription start sites accompanied by a similar enrichment of activating histone marks near those sites. Disruption of p53-p300 interaction by a site-directed peptide inhibitor abolished autoacetylated p300-mediated enhanced histone acetylation, suggesting a crucial role played by the allosteric activation in p53-mediated gene regulation. Gain-of-function mutant p53, known to impart aggressive proliferative properties in tumor cells, also activate p300 autoacetylation. The same peptide abolished many of the gain-of-functions of mutant p53 as well. We conclude that allosteric activation of p300 by p53 underpins gene regulation by p53. Reversal of gain-of-function properties of mutant p53 suggests that molecules targeting the p53-p300 interface may be good candidates for anti-tumor drugs.

molecular biology↗