Tatiana Moiseeva

• PhD
• Principal Investigator at Tallinn University of Technology

ATR kinase activity slows replication forks and prevents origin firing in damaged cells. Here we describe proteomic analyses that identified mechanisms through which ATR kinase inhibitors induce unscheduled origin firing in undamaged cells. ATR-Chk1 inhibitor-induced origin firing is mediated by Cdc7 kinase through previously undescribed phosphoryl...

DNA damage-induced signaling by ATR and CHK1 inhibits DNA replication, stabilizes stalled and collapsed replication forks, and mediates the repair of multiple classes of DNA lesions. We and others have shown that ATR kinase inhibitors, three of which are currently undergoing clinical trials, induce excessive origin firing during unperturbed DNA rep...

Mechanisms that limit origin firing are essential as the ˜50,000 origins that replicate the human genome in unperturbed cells are chosen from an excess of ˜500,000 licensed origins. Computational models of the spatiotemporal pattern of replication foci assume that origins fire stochastically with a domino-like progression that places later firing o...

DNA polymerase epsilon (PolE) in an enzyme essential for DNA replication. Deficiencies and mutations in PolE cause severe developmental abnormalities and cancers. Paradoxically, the catalytic domain of yeast PolE catalytic subunit is dispensable for survival, and its non-catalytic essential function is linked with replicative helicase (CMG) assembl...

TIMELESS protein (TIM) protects replication forks from stalling at difficult-to-replicate regions and plays an important role in DNA damage response, including checkpoint signaling, protection of stalled replication forks and DNA repair. Loss of TIM causes severe replication stress, while its overexpression is common in various types of cancer, pro...

ATR kinase is a central regulator of the DNA damage response (DDR) and cell cycle checkpoints. ATR kinase inhibitors (ATRi's) combine with radiation to generate CD8⁺ T cell-dependent responses in mouse models of cancer. We show that ATRi's induce cyclin-dependent kinase 1 (CDK1)-dependent origin firing across active replicons in CD8⁺ T cells activa...

DNA polymerase epsilon in an essential enzyme, responsible for the synthesis of the leading strand during DNA replication. Deficiencies and mutations in DNA polymerase epsilon catalytic subunit (POLE1) cause severe developmental abnormalities and cancers. Paradoxically, the non-catalytic C-terminal domain of yeast polymerase epsilon catalytic subun...

ATR kinase is a central regulator of the DNA damage response (DDR) and cell cycle checkpoints. However, little is known about the role of ATR in the cell cycle and the impact of DDR inhibitors in immune cells in the absence of DNA damage. We previously showed that the ATR inhibitor AZD6738 (ATRi) combines with radiation to generate delayed, CD8+ T...

We demonstrate that activated CD8+ T cells from Pmel mice replicate their genome within 4 hours which is significantly faster than most cancer cells. Many genotoxic chemotherapeutic agents target the rapid proliferation of cancer cells. However, activated T cells also expand rapidly and this can lead to lymphopenia in patients receiving these chemo...

WEE1 kinase is a key regulator of the G2/M transition. The WEE1 kinase inhibitor AZD1775 (WEE1i) induces origin firing in replicating cells. We show that WEE1i induces CDK1-dependent RIF1 phosphorylation and CDK2- and CDC7-dependent activation of the replicative helicase. WEE1 suppresses CDK1 and CDK2 kinase activities to regulate the G1/S transiti...

RAD51 plays a central role in homologous recombination during double-strand break repair and in replication fork dynamics. Misregulation of RAD51 is associated with genetic instability and cancer. RAD51 is regulated by many accessory proteins including the highly conserved Shu complex. Here, we report the function of the human Shu complex during re...

ATR kinase is activated by RPA-coated single-stranded DNA (ssDNA) to orchestrate DNA damage responses. Here we show that ATR inhibition differs from ATR loss. Mouse model expressing kinase-dead ATR (Atr+/KD), but not loss of ATR (Atr+/−), displays ssDNA-dependent defects at the non-homologous region of X-Y chromosomes during male meiosis leading to...

The origin of species would not have been possible without high fidelity DNA replication and complex genomes evolved with mechanisms that control the initiation of DNA replication at multiple origins on multiple chromosomes such that the genome is duplicated once and only once. The mechanisms that control the assembly and activation of the replicat...

We describe a dynamic phosphorylation on serine-1940 of the catalytic subunit of human Pol ε, POLE1, following DNA damage. We also describe novel interactions between POLE1 and the iron-sulfur cluster assembly complex CIA proteins CIAO1 and MMS19. We show that serine-1940 is essential for the interaction between POLE1 and MMS19, but not POLE1 and C...

The proteasome is the main intracellular proteolytic machine involved in the regulation of numerous cellular processes, including gene expression. In addition to their proteolytic activity, proteasomes also exhibit ATPase/helicase (the 19S particle) and RNAse (the 20S particle) activities, which are regulated by post-translational modifications. In...

Proteasomes act as the main apparatus of non-lysosomal intracellular proteolysis and participate in the regulation of most important cellular processes. Despite considerable progress in the understanding of proteasome's functioning, some issues, in particular, RNase activity of these ribonucleoprotein complexes and its regulation remain scarcely ex...

Proteasomes function as the main nonlysosomal machinery of intracellular proteolysis and are involved in the regulation of the majority of important cellular processes. Despite the considerable progress that has been made in understanding the functioning of proteasomes, some issues (in particular, the RNase activity of these ribonucleoprotein compl...

Stability of proteins is largely controlled by post-translational covalent modifications. Among those, ubiquitylation plays a central role as it marks the proteins for proteasome-dependent degradation. Proteolytic activities of proteasomes are critical for execution of various cellular processes, including DNA damage signaling and repair. However,...

The 26S proteasome is a large multi-subunit protein complex that exerts specific degradation of proteins in the cell. The 26S proteasome consists of the 20S proteolytic particle and the 19S regulator. In order to be targeted for proteasomal degradation most of the proteins must undergo the post-translational modification of poly-ubiquitination. How...

26S proteasome is a multisubunit protein complex that consists of 19S regulatory and 20S catalytic subcomplexes. The primary proteasome cellular function is protein degradation. It has recently been found that, in addition to its proteolytic activities, the 20S particle also displays endoribonuclease activity mediated by two alpha-type subunits, α1...

26S proteasome is a large multi-subunit protein complex involved in proteolytic degradation of proteins. In addition to its canonical proteolytic activity, the proteasome is also associated with recently characterized endoribonuclease (endo- RNAse) activity. However, neither functional significance, nor the mechanisms of its regulation are currentl...

26S proteasome is a multisubunit protein complex that plays a pivotal role in protein degradation. Proteasome's enzymatic activities - proteolytic, ATPase/helicase and RNase - can be used in regulation of multiple cellular processes. Recent studies confirm the major role of proteasomes in transcriptional regulation. Although various post-translatio...

26S proteasome is a multi-subunit protein complex that consists of the regulatory 19S and the catalytic 20S subcomplexes. The major cellular function of the proteasome is protein degradation. It has been found recently that the 20S particle, besides its proteolytic activity, also possesses endoribonuclease activity. The latter is mediated by two al...

The 26S proteasome is an abundant multi-subunit complex, which, in addition to lysosomes, represents a major cellular "protein degradation factory". The proteasome complex possesses protease, ATPase/helicase, and RNAse enzymatic activities, which are used by the latter to regulate various physiological processes. Recent findings have revealed an im...

Here we have studied changes in the subunit composition, phosphorylation state and enzymatic activities of 26S proteasomes in cells undergoing the programmed cell death. Apoptosis in proerythroleukemic K562 cells was induced by glutathione-depleting agent, diethylmaleate (DEM). We have shown for the first time that proteasomes isolated from the nuc...

The specificity of 26S proteasomes' endoribonuclease activity has been shown to be changed under effect of erythroid differentiation (hemin) and programmed cell death (diethylmaleate) inductors in proerythroleukemic K562 cells. Treatment of K562 cells with apoptosis and differentiation inductors leads to the specific stimulation of RNase activity t...

In the present work, changes in the subunit composition, phosphorylation state, and enzymatic activities of 26S proteasomes undergoing programmed cell death were studied. Apoptosis in proerythroleukemic K562 cells was induced by the glutathione-depleting agent, diethylmaleate (DEM). We have shown for the first time that proteasomes isolated from th...

The specificity of the 26S proteasome endoribonuclease activity in proerythroleukemic K562 cells has been shown to change under the effects of inducers of erythroid differentiation inducers led to specific stimulation of RNase activity for certain mRNAs and to reduction of proteasome RNase activity for other mRNAs. The studied enzymatic activity wa...

The participation of proteasome in the programmed cells death is now extensively investigated. Studies using selective inhibitors of proteasomes have provided a direct evidence of both pro- and anti-apoptotic functions of proteasomes. Such opposite roles of 26S proteasomes in regulation of apoptosis may be defined by the proliferative state of cell...