Biology subjects

Tarakhovsky, A.

Publications and source records attributed to Tarakhovsky, A..

5 recordsLinked to original sources

bioRxiv2024

Chromatin mimicry by human JC virus

Chronically persistent viruses are integral components of the organismal ecosystem in humans and animals 1 2. Many of these viruses replicate and accumulate within the cell nucleus 3. The nuclear location allows viruses to evade cytoplasmic host viral sensors and promotes viral replication 4. One of the unexplored and puzzling aspects of the viral nuclear lifecycle involves the viruss ability to deal with the physical constraints of nuclear architecture. To replicate and accumulate within the nucleus in large numbers sufficient for infection spreading, DNA viruses need to overcome the spatial limitations imposed by chromatin and the nuclear matrix. We found that one of the most widespread and potentially lethal human viruses, the JC polyomavirus 5, interferes with nuclear heterochromatin to create virus-occupied space. The JC viruss impact on heterochromatin is mediated by the viral nonstructural protein, Agnoprotein (Agno). Agnos interference with heterochromatin is governed by structurally diverse mimics of host epigenetic regulators that facilitate virus-induced chromatin reorganization and a dramatic decline in nuclear stiffness in the infected cells. The JCV epigenetic mimicry is critical for the virus infection, as evident from reduced replication of mimic-mutant viruses. Our data suggest that modulation of nuclear mechanical properties is a novel strategy enabling chronicity of the JC and possibly other nuclear virus infections.

microbiology↗

bioRxiv2023

Transcriptional shut-off of MAP kinase signaling enables pluripotency maintenance during diapause

Exposure of unicellular or multicellular organisms to adverse environmental conditions, including nutrient deprivation, may induce a state of suspended animation or diapause. The diapause minimizes the organisms reliance on external energy sources and ensures survival. Among different forms of diapause, embryonic diapause, caused by a limited supply of nutrients to the growing embryos, is particularly challenging for the organism. Diapause embryos stop developing at the peak of pluripotent cell differentiation and maintain this undifferentiated yet entirely vital state despite the overall reduction in anabolic processes and genome-wide transcriptional repression. Using ES cells commonly employed to study the mechanism of embryonic diapause, we solve the paradox of the cell maintenance in an undifferentiated ES cell state during diapause. We find that broad transcriptional repression by long-term inhibition of the bromodomain and extra-terminal (BET) proteins causes diapause. These diapause ES cells upregulate a functionally linked group of genes encoding negative regulators of MAP kinase signaling (NRMKS), which play a crucial role in ES cell differentiation. We find that elevated NRMKS expression is a hallmark of the diapause cells and cells exposed to diapause-inducing conditions, including mTOR inhibition, and is required for the maintenance of ES cell pluripotency during diapause. Mechanistically, exposure of ES cells to diapause-inducing conditions leads to rapid decline of the Capicua transcriptional repressor (CIC) at the NRMKS gene promoters, followed by transcriptional upregulation of NRMKS genes. The mTOR and BET-dependent transcriptional switch supporting the undifferentiated state of the diapause ES cells suggests a broader usage of this mechanism in maintaining the undifferentiated state of metabolically dormant stem- or stem-like cells in different tissues.

cell biology↗

bioRxiv2023

Control of enhancer activation in the type I interferon response by the histone demethylase Kdm4d/JMJD2d

Transcriptional activation depends on the interplay of chromatin modifiers to establish a permissive epigenetic landscape. While histone 3 lysine 9 (H3K9) methylation has long been associated with gene repression, there is limited evidence to support a role for H3K9 demethylases in gene activation. Here we describe the H3K9 demethylase Kdm4d/JMJD2d as a positive regulator of type I interferon responses. In mouse embryonic fibroblasts (MEFs), depletion of JMJD2d attenuates the transcriptional response, conferring increased viral susceptibility, while overexpression of the demethylase results in more robust IFN activation. We find that the underlying mechanism of JMJD2d in type I interferon responses consists of an effect both on the transcription of enhancer RNAs (eRNAs) and on dynamic H3K9me2 at associated promoters. In support of these findings, we establish that JMJD2d is associated with enhancer regions throughout the genome prior to stimulation but is redistributed to inducible promoters in conjunction with transcriptional activation. Taken together, our data reveal JMJD2d as a chromatin modifier that connects enhancer transcription with promoter demethylation to modulate transcriptional responses.

immunology↗

bioRxiv2020

A histone-like motif in yellow fever virus contributes to viral replication

The mimicry of host proteins by viruses contributes to their ability to suppress antiviral immunity and hijack host biosynthetic machinery1. Host adaptation to evade this exploitation depends on host protein functional redundancy2. Non-redundant, essential host proteins have limited potential to adapt without severe consequences3. Histones, which are essential for genome architecture and control of gene expression, are among the most evolutionary conserved proteins4. Here we show that the capsid protein of the flavivirus yellow fever virus (YFV), mimics histone H4 and interferes with chromatin gene regulation by BRD4, a bromodomain and extraterminal domain (BET) protein. Two acetyl-lysine residues of YFV capsid are embedded in a histone-like motif that interacts with the BRD4 bromodomain, affecting gene expression and influencing YFV replication. These findings reveal histone mimicry as a strategy employed by an RNA virus that replicates in the cytosol5 and define convergent and distinct molecular determinants for motif recognition of the viral mimic versus histone H4.

microbiology↗

bioRxiv2019

Histone methyltransferase MMSET/NSD2 is essential for generation of B1 cell compartment in mice

Humoral immunity in mice and man relies on the function of two developmentally and functionally distinct B cell subsets - B1 and B2 cells. While B2 cells are responsible for most of the adaptive response to environmental antigens, B1 cells, which are comprised of phenotypically distinct B1a and B1b cells, are carriers of the innate humoral immunity that relies on production of poly-reactive and low affinity antibodies. The molecular mechanism of B cell specification into different subsets is not well established. Here we identified lysine methyltransferase MMSET/NSD2 as a critical regulator of the B1 cell population. We show that NSD2 deficiency in B cell precursors prevents generation of the B1 cell compartment, while having a minor impact on B2 cells. Our data revealed MMSET/NSD2, which catalyzes histone H3 lysine 36 di-methylation, as the first in class epigenetic master regulator of a major B cell lineage in mice.

immunology↗