The role of hexokinases in epigenetic regulation: altered hexokinase expression and chromatin stability in yeast.

Background: Human hexokinase 2 (HK2) plays an important role in regulating Warburg effect, which metabolizes glucose to lactate acid even in the presence of ample oxygen and provides intermediate metabolites to support cancer cell proliferation and tumor growth. HK2 overexpression has been observed in various types of cancers and targeting HK2-driven Warburg effect has been suggested as a potential cancer therapeutic strategy. Given that epigenetic enzymes utilize metabolic intermediates as substrates or co-factors to carry out post-translational modification of histones and nucleic acids modifications in cells, we hypothesized that altering HK2 expression could impact the epigenome and, consequently, chromatin stability in yeast.

DNA polymerase delta governs parental histone transfer to DNA replication lagging strand.

Chromatin replication is intricately intertwined with the recycling of parental histones to the newly duplicated DNA strands for faithful genetic and epigenetic inheritance. The transfer of parental histones occurs through two distinct pathways: leading strand deposition, mediated by the DNA polymerase ε subunits Dpb3/Dpb4, and lagging strand deposition, facilitated by the MCM helicase subunit Mcm2. However, the mechanism of the facilitation of Mcm2 transferring parental histones to the lagging strand while moving along the leading strand remains unclear.

Defective transfer of parental histone decreases frequency of homologous recombination by increasing free histone pools in budding yeast.

Recycling of parental histones is an important step in epigenetic inheritance. During DNA replication, DNA polymerase epsilon subunit DPB3/DPB4 and DNA replication helicase subunit MCM2 are involved in the transfer of parental histones to the leading and lagging strands, respectively. Single Dpb3 deletion (dpb3Δ) or Mcm2 mutation (mcm2-3A), which each disrupts one parental histone transfer pathway, leads to the other's predominance.

The Role of Hexokinases in Epigenetic Regulation: Altered Hexokinase Expression and Chromatin Stability in Yeast.

. Human hexokinase 2 ( ) plays an important role in regulating Warburg effect, which metabolizes glucose to lactate acid even in the presence of ample oxygen and provides intermediate metabolites to support cancer cell proliferation and tumor growth. overexpression has been observed in various types of cancers and targeting -driven Warburg effect has been suggested as a potential cancer therapeutic strategy.

Defective transfer of parental histone decreases frequency of homologous recombination in budding yeast.

Recycling of parental histones is an important step in epigenetic inheritance. During DNA replication, DNA polymerase epsilon subunit DPB3/DPB4 and DNA replication helicase subunit MCM2 are involved in the transfer of parental histones to the leading and lagging DNA strands, respectively. Single deletion ( ) or mutation ( ), which each disrupt one parental histone transfer pathway, leads to the other's predominance.

Mitochondria in Ovarian Aging and Reproductive Longevity.

Mitochondrial dysfunction is one of the hallmarks of aging. Consistently mitochondrial DNA (mtDNA) copy number and function decline with age in various tissues. There is increasing evidence to support that mitochondrial dysfunction drives ovarian aging.

Adaptation of Mge1 to oxidative stress by local unfolding and altered Interaction with mitochondrial Hsp70 and Mxr2.

Perturbations in mitochondrial redox levels oxidize nucleotide exchanger Mge1, compromising its ability to bind to the Hsp70, while the Mxr2 enzyme reduces the oxidized Mge1. However, the effects of persistent oxidative stress on Mge1 structure and function are not known. In this study, we show that oxidation-induced selective and local structural adaptations cause the detachment of Mge1 from Hsp70.

A conserved R type Methionine Sulfoxide Reductase reverses oxidized GrpEL1/Mge1 to regulate Hsp70 chaperone cycle.

Cells across evolution employ reversible oxidative modification of methionine and cysteine amino acids within proteins to regulate responses to redox stress. Previously we have shown that mitochondrial localized methionine sulfoxide reductase (Mxr2) reversibly regulates oxidized yeast Mge1 (yMge1), a co-chaperone of Hsp70/Ssc1 to maintain protein homeostasis during oxidative stress. However, the specificity and the conservation of the reversible methionine oxidation mechanism in higher eukaryotes is debatable as human GrpEL1 (hGrpEL1) unlike its homolog yMge1 harbors two methionine residues and multiple cysteines besides the mammalian mitochondria hosting R and S types of Mxrs/Msrs.

A Single Point Mutation in Mitochondrial Hsp70 Cochaperone Mge1 Gains Thermal Stability and Resistance.

Mge1, a yeast homologue of Escherichia coli GrpE, is an evolutionarily conserved homodimeric nucleotide exchange factor of mitochondrial Hsp70. Temperature-dependent reversible structural alteration from a dimeric to a monomeric form is critical for Mge1 to act as a thermosensor. However, very limited information about the structural component or amino acid residue(s) that contributes to thermal sensing of Mge1/GrpE is available.

Methionine sulfoxide reductase 2 reversibly regulates Mge1, a cochaperone of mitochondrial Hsp70, during oxidative stress.

Peptide methionine sulfoxide reductases are conserved enzymes that reduce oxidized methionines in protein(s). Although these reductases have been implicated in several human diseases, there is a dearth of information on the identity of their physiological substrates. By using Saccharomyces cerevisiae as a model, we show that of the two methionine sulfoxide reductases (MXR1, MXR2), deletion of mitochondrial MXR2 renders yeast cells more sensitive to oxidative stress than the cytosolic MXR1.

Structural analysis of the mutant protein D26G of human γS-crystallin, associated with Coppock cataract.

Purpose: To analyze the protein structural features responsible for the aggregation properties of the mutant protein D26G human γS-crystallin (HGSC) associated with congenital Coppock-type cataract.

Methods: cDNAs of wild-type (WT) and D26G mutant HGSC were cloned and expressed in BL21 (DE3) pLysS cells and the proteins isolated and purified. Their secondary and tertiary structural features, aggregation tendencies, and structural stabilities were compared using spectroscopic (circular dichroism, intrinsic and extrinsic fluorescence), molecular modeling, and dynamics methods.