ABSTRACT
Nucleoli, the largest subnuclear compartments, are formed around arrays of ribosomal gene repeats transcribed by RNA polymerase I. The primary function of nucleoli is ribosome biogenesis. Specific DNA damage response mechanisms exist to maintain the genomic stability of ribosomal repeats. Here, we provide a snapshot of our current understanding of processes involved in nucleolar DNA damage response. We discuss structure and function of ribosomal repeats, techniques developed for studying DNA damage response in nucleoli, as well as molecular mechanisms of DNA damage-induced repression of nucleolar transcription and nucleoli reorganization.
Subject(s)
Cell Nucleolus , Genomic Instability , Cell Nucleolus/genetics , DNA Damage , DNA, Ribosomal , Humans , RNA, Ribosomal , RibosomesABSTRACT
Recent studies have significantly expanded our understanding of the mechanisms of L-ascorbic acid (ASC, vitamin C) action, leading to the emergence of several hypotheses that validate the possibility of using ASC in clinical practice. ASC may be considered an epigenetic drug capable of reducing aberrant DNA and histone hypermethylation, which could be helpful in the treatment of some cancers and neurodegenerative diseases. The clinical potency of ASC is also associated with regenerative medicine; in particular with the production of iPSCs. The effect of ASC on somatic cell reprogramming is most convincingly explained by a combined enhancement of the activity of the enzymes involved in the active demethylation of DNA and histones. This review describes how ASC can affect the epigenetic status of a cell and how it can be used in anticancer therapy and stem cell reprogramming.
ABSTRACT
Reactions of genetically identical cells to various exogenous and endogenous stimuli can vary significantly. One of the main factors of this non-genetic cellular heterogeneity is the cell cycle. The most convenient way to study the subcellular processes depending on the cell cycle stage is the synchronization of the cells. Toxic inhibitors of DNA replication and/or mitotic spindle assembly are typically used to synchronize cells. It is important to accurately select the synchronization method for a particular experiment. In this study, we performed a comparative analysis of the synchronization methods of normal and transformed human cells, paying special attention to the accuracy of synchronization and toxicity of the methods used.
Subject(s)
Cell Cycle , DNA Replication , Cell Line, Transformed , Humans , Mitosis , Spindle ApparatusABSTRACT
Although the heat-stress response has been extensively studied for decades, very little is known about its effects on nucleic acids and nucleic acid-associated processes. This is due to the fact that the research has focused on the study of heat shock proteins and factors (HSPs and HSFs), their involvement in the regulation of transcription, protein homeostasis, etc. Recently, there has been some progress in the study of heat stress effects on DNA integrity. In this review, we summarize and discuss well-known and potential mechanisms of formation of various heat stress-induced DNA damage.
ABSTRACT
Heat stress is one of the most popular models for studying the regulation of gene expression. For decades, researchers' attention was focused on the study of the mechanisms of transcriptional activation of stress-induced genes. Although the phenomenon of heat stress-induced global transcriptional repression is known for a long time, the exact molecular mechanisms of such a repression are poorly explored. In this mini-review, we attempt to summarize the existing experimental data on heat stress-induced transcriptional repression.
Subject(s)
Heat-Shock Response/genetics , Transcription, Genetic/physiology , Animals , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , Hot Temperature , Promoter Regions, Genetic , Transcriptional ActivationABSTRACT
Using indirect immunofluorescence, in this study we showed that the constitutive heat shock protein HSC70 forms granule-like structures in the cytoplasm of human cells several days after the exposure to heat stress. It was shown that this effect is not the result of HSC70 overexpression under heat stress and is not due to the formation of hyperthermia-induced translational stress granules in the cytoplasm.
Subject(s)
Cytoplasmic Granules/metabolism , HSC70 Heat-Shock Proteins/metabolism , Heat-Shock Response , Humans , MCF-7 Cells , Time FactorsABSTRACT
Cys2His2 (C2H2)-type zinc fingers are widespread DNA binding motifs in eukaryotic transcription factors. Zinc fingers are short protein motifs composed of two or three ß-layers and one α-helix. Two cysteine and two histidine residues located in certain positions bind zinc to stabilize the structure. Four other amino acid residues localized in specific positions in the N-terminal region of the α-helix participate in DNA binding by interacting with hydrogen donors and acceptors exposed in the DNA major groove. The number of zinc fingers in a single protein can vary over a wide range, thus enabling variability of target DNA sequences. Besides DNA binding, zinc fingers can also provide protein-protein and RNA-protein interactions. For the most part, proteins containing the C2H2-type zinc fingers are trans regulators of gene expression that play an important role in cellular processes such as development, differentiation, and suppression of malignant cell transformation (oncosuppression).
Subject(s)
Multigene Family , Transcription Factors/chemistry , Transcription Factors/metabolism , Animals , Humans , Molecular Sequence Data , Transcription Factors/classification , Transcription Factors/genetics , Zinc FingersSubject(s)
Core Binding Factor Alpha 2 Subunit/genetics , DNA Fragmentation , Introns/genetics , Transcriptional Activation/genetics , Core Binding Factor Alpha 2 Subunit/deficiency , Core Binding Factor Alpha 2 Subunit/metabolism , Enhancer Elements, Genetic/genetics , Gene Silencing , HEK293 Cells , Histones/genetics , Histones/metabolism , Humans , Jurkat Cells , Nuclear Matrix/metabolismABSTRACT
Transcription factor RUNX1 is one of the key regulatory proteins in vertebrates. It controls hematopoiesis and angiogenesis. It is indispensable during embryogenesis for the emergence of sites of definitive hematopoiesis and later in mature organisms for bone marrow blood stem cells differentiation. Moreover, RUNX1 gene is a frequent target for chromosomal translocations which cause acute forms of leukemia. A lot of types of human leukemia are somehow associated with mutations in this gene. Nevertheless, to this day the precise mechanism guiding the tissue-specific manner of the RUNX1 gene expression remains unknown. In this review we tried to summarize all the experimental data accumulated during the past twenty years beginning from the date when the cDNA sequence of the RUNX1 gene was first annotated. In the first part of the review we shall focus on structure, isoforms, covalent modifications of the RUNX1 transcription factor and its participation in different regulatory cascades. In the second part we shall discuss expression regulation, mutations and chromosomal translocations of the RUNX1 gene.
Subject(s)
Core Binding Factor Alpha 2 Subunit , Gene Expression Regulation, Leukemic , Leukemia , Mutation , Neoplasm Proteins , Protein Processing, Post-Translational , Translocation, Genetic , Acute Disease , Animals , Core Binding Factor Alpha 2 Subunit/biosynthesis , Core Binding Factor Alpha 2 Subunit/genetics , Embryonic Development/physiology , Hematopoiesis/physiology , Humans , Leukemia/genetics , Leukemia/metabolism , Neoplasm Proteins/biosynthesis , Neoplasm Proteins/genetics , Neovascularization, Physiologic/physiology , Protein Isoforms/biosynthesis , Protein Isoforms/geneticsABSTRACT
The spatial organization of a 250 Kb region of chicken chromosome 14, which includes the alpha globin gene cluster, was studied using in situ hybridization of a corresponding BAC probe with nuclear halos. It was found that in non-erythroid cells (DT40) and cultured erythroid cells of definite lineage (HD3) the genomic region under study was partially (DT40 cells) or fully (HD3 cells) associated with the nuclear matrix. In contrast, in embryonic red blood cells (10-day RBC) the same area was located in the crown of DNA loops surrounding the nuclear matrix, although both globin genes and surrounding house-keeping genes were actively transcribed in these cells. This spatial organization was associated with the virtual absence of RNA polymerase II in nuclear matrices prepared from 10-day RBC. In contrast, in HD3 cells a significant portion of RNA polymerase II was present in nuclear matrices. Taken together, these observations suggest that in embryonic erythroid cells transcription does not occur in association with the nuclear matrix.
Subject(s)
Erythrocytes/metabolism , Nuclear Matrix/metabolism , Transcription, Genetic , alpha-Globins/genetics , Animals , Cells, Cultured , Chick Embryo , Chickens/genetics , Nuclear Matrix/enzymology , RNA Polymerase II/metabolismABSTRACT
Using semi-quantitative PCR-based approach, we have shown that the breakpoint cluster region of the AML1 gene was associated with the nuclear matrix. We have demonstrated that inhibition of topoisomerase II by etoposide stimulates the appearance of histone gammaH2AX foci, an indicator for the presence of DNA double-strand breaks. Furthermore, the major part of these foci was associated with the nuclear matrix. We also visualized nuclear matrix--associated multiprotein complexes involved in topoisomerase II--induced DNA double-strand break repair. Colocalization studies have demonstrated that these complexes included the principal components of the non-homologous end joining repair system (Ku80, DNA-PKcs and DNA ligase IV). Thus, it is reasonable to suggest that the non-homologous DNA end joining is a possible mechanism of topoisomerase II--induced chromosomal rearrangements.
