Spatiotemporal higher-order chromatin landscape of human histone gene clusters at histone locus bodies during the cell cycle in breast cancer progression.

Human Histone Locus Bodies (HLBs) are nuclear subdomains comprised of clustered histone genes that are coordinately regulated throughout the cell cycle. We addressed temporal-spatial higher-order genome organization for time-dependent chromatin remodeling at HLBs that supports control of cell proliferation. Proximity distances of specific genomic contacts within histone gene clusters exhibit subtle changes during the G1 phase in MCF10 breast cancer progression model cell lines.

Spatiotemporal Epigenetic Control of the Histone Gene Chromatin Landscape during the Cell Cycle.

Higher-order genomic organization supports the activation of histone genes in response to cell cycle regulatory cues that epigenetically mediates stringent control of transcription at the G1/S-phase transition. Histone locus bodies (HLBs) are dynamic, non-membranous, phase-separated nuclear domains where the regulatory machinery for histone gene expression is organized and assembled to support spatiotemporal epigenetic control of histone genes. HLBs provide molecular hubs that support synthesis and processing of DNA replication-dependent histone mRNAs.

Epigenetic-Mediated Regulation of Gene Expression for Biological Control and Cancer: Fidelity of Mechanisms Governing the Cell Cycle.

The cell cycle is governed by stringent epigenetic mechanisms that, in response to intrinsic and extrinsic regulatory cues, support fidelity of DNA replication and cell division. We will focus on (1) the complex and interdependent processes that are obligatory for control of proliferation and compromised in cancer, (2) epigenetic and topological domains that are associated with distinct phases of the cell cycle that may be altered in cancer initiation and progression, and (3) the requirement for mitotic bookmarking to maintain intranuclear localization of transcriptional regulatory machinery to reinforce cell identity throughout the cell cycle to prevent malignant transformation.

Epigenetic-Mediated Regulation of Gene Expression for Biological Control and Cancer: Cell and Tissue Structure, Function, and Phenotype.

Epigenetic gene regulatory mechanisms play a central role in the biological control of cell and tissue structure, function, and phenotype. Identification of epigenetic dysregulation in cancer provides mechanistic into tumor initiation and progression and may prove valuable for a variety of clinical applications. We present an overview of epigenetically driven mechanisms that are obligatory for physiological regulation and parameters of epigenetic control that are modified in tumor cells.

Inhibition of the RUNX1-CBFβ transcription factor complex compromises mammary epithelial cell identity: a phenotype potentially stabilized by mitotic gene bookmarking.

RUNX1 has recently been shown to play an important role in determination of mammary epithelial cell identity. However, mechanisms by which loss of the RUNX1 transcription factor in mammary epithelial cells leads to epithelial-to-mesenchymal transition (EMT) are not known. Here, we report that interaction between RUNX1 and its heterodimeric partner CBFβ is essential for sustaining mammary epithelial cell identity.

Author Correction: Temporal dynamic reorganization of 3D chromatin architecture in hormone-induced breast cancer and endocrine resistance.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

RUNX1 and RUNX2 transcription factors function in opposing roles to regulate breast cancer stem cells.

Breast cancer stem cells (BCSCs) are competent to initiate tumor formation and growth and refractory to conventional therapies. Consequently BCSCs are implicated in tumor recurrence. Many signaling cascades associated with BCSCs are critical for epithelial-to-mesenchymal transition (EMT).

Identification of tRNA-derived small RNA (tsRNA) responsive to the tumor suppressor, RUNX1, in breast cancer.

Despite recent advances in targeted therapies, the molecular mechanisms driving breast cancer initiation, progression, and metastasis are minimally understood. Growing evidence indicate that transfer RNA (tRNA)-derived small RNAs (tsRNA) contribute to biological control and aberrations associated with cancer development and progression. The runt-related transcription factor 1 (RUNX1) transcription factor is a tumor suppressor in the mammary epithelium whereas RUNX1 downregulation is functionally associated with breast cancer initiation and progression.

Temporal dynamic reorganization of 3D chromatin architecture in hormone-induced breast cancer and endocrine resistance.

Recent studies have demonstrated that chromatin architecture is linked to the progression of cancers. However, the roles of 3D structure and its dynamics in hormone-dependent breast cancer and endocrine resistance are largely unknown. Here we report the dynamics of 3D chromatin structure across a time course of estradiol (E2) stimulation in human estrogen receptor α (ERα)-positive breast cancer cells.

Chromosome territories and the global regulation of the genome.

Spatial positioning is a fundamental principle governing nuclear processes. Chromatin is organized as a hierarchy from nucleosomes to Mbp chromatin domains (CD) or topologically associating domains (TADs) to higher level compartments culminating in chromosome territories (CT). Microscopic and sequencing techniques have substantiated chromatin organization as a critical factor regulating gene expression.

RUNX1-dependent mechanisms in biological control and dysregulation in cancer.

The RUNX1 transcription factor has recently been shown to be obligatory for normal development. RUNX1 controls the expression of genes essential for proper development in many cell lineages and tissues including blood, bone, cartilage, hair follicles, and mammary glands. Compromised RUNX1 regulation is associated with many cancers.

Suppression of Breast Cancer Stem Cells and Tumor Growth by the RUNX1 Transcription Factor.

Breast cancer remains the most common malignant disease in women worldwide. Despite advances in detection and therapies, studies are still needed to understand the mechanisms underlying this cancer. Cancer stem cells (CSC) play an important role in tumor formation, growth, drug resistance, and recurrence.

Epithelial-to-mesenchymal transition and cancer stem cells contribute to breast cancer heterogeneity.

Breast cancer is the most common cancer in women, and accounts for ~30% of new cancer cases and 15% of cancer-related deaths. Tumor relapse and metastasis are primary factors contributing to breast cancer-related deaths. Therefore, the challenge for breast cancer treatment is to sustain remission.

Nuclear organization mediates cancer-compromised genetic and epigenetic control.

Nuclear organization is functionally linked to genetic and epigenetic regulation of gene expression for biological control and is modified in cancer. Nuclear organization supports cell growth and phenotypic properties of normal and cancer cells by facilitating physiologically responsive interactions of chromosomes, genes and regulatory complexes at dynamic three-dimensional microenvironments. We will review nuclear structure/function relationships that include: 1.

Higher order genomic organization and regulatory compartmentalization for cell cycle control at the G1/S-phase transition.

Fidelity of histone gene regulation, and ultimately of histone protein biosynthesis, is obligatory for packaging of newly replicated DNA into chromatin. Control of histone gene expression within the 3-dimensional context of nuclear organization is reflected by two well documented observations. DNA replication-dependent histone mRNAs are synthesized at specialized subnuclear domains designated histone locus bodies (HLBs), in response to activation of the growth factor dependent Cyclin E/CDK2/HINFP/NPAT pathway at the G1/S transition in mammalian cells.

Intranuclear and higher-order chromatin organization of the major histone gene cluster in breast cancer.

Alterations in nuclear morphology are common in cancer progression. However, the degree to which gross morphological abnormalities translate into compromised higher-order chromatin organization is poorly understood. To explore the functional links between gene expression and chromatin structure in breast cancer, we performed RNA-seq gene expression analysis on the basal breast cancer progression model based on human MCF10A cells.

Selective expression of long non-coding RNAs in a breast cancer cell progression model.

Long non-coding RNAs (lncRNAs) are acknowledged as regulators of cancer biology and pathology. Our goal was to perform a stringent profiling of breast cancer cell lines that represent disease progression. We used the MCF-10 series, which includes the normal-like MCF-10A, HRAS-transformed MCF-10AT1 (pre-malignant), and MCF-10CA1a (malignant) cells, to perform transcriptome wide sequencing.

Runx1 stabilizes the mammary epithelial cell phenotype and prevents epithelial to mesenchymal transition.

Runx1 is a well characterized transcription factor essential for hematopoietic differentiation and Runx1 mutations are the cause of leukemias. Runx1 is highly expressed in normal epithelium of most glands and recently has been associated with solid tumors. Notably, the function of Runx1 in the mammary gland and how it is involved in initiation and progression of breast cancer is still unclear.

SMARCA4 regulates gene expression and higher-order chromatin structure in proliferating mammary epithelial cells.

The packaging of DNA into chromatin plays an important role in transcriptional regulation and nuclear processes. Brahma-related gene-1 SMARCA4 (also known as BRG1), the essential ATPase subunit of the mammalian SWI/SNF chromatin remodeling complex, uses the energy from ATP hydrolysis to disrupt nucleosomes at target regions. Although the transcriptional role of SMARCA4 at gene promoters is well-studied, less is known about its role in higher-order genome organization.

Large-scale probabilistic 3D organization of human chromosome territories.

There is growing evidence that chromosome territories (CT) have a probabilistic non-random arrangement within the cell nucleus of mammalian cells including radial positioning and preferred patterns of interchromosomal interactions that are cell-type specific. While it is generally assumed that the three-dimensional (3D) arrangement of genes within the CT is linked to genomic regulation, the degree of non-random organization of individual CT remains unclear. As a first step to elucidating the global 3D organization (topology) of individual CT, we performed multi-color fluorescence in situ hybridization using six probes extending across each chromosome in human WI38 lung fibroblasts.

Chromosomes at Work: Organization of Chromosome Territories in the Interphase Nucleus.

The organization of interphase chromosomes in chromosome territories (CTs) was first proposed more than one hundred years ago. The introduction of increasingly sophisticated microscopic and molecular techniques, now provide complementary strategies for studying CTs in greater depth than ever before. Here we provide an overview of these strategies and how they are being used to elucidate CT interactions and the role of these dynamically regulated, nuclear-structure building blocks in directly supporting nuclear function in a physiologically responsive manner.

C-ing the Genome: A Compendium of Chromosome Conformation Capture Methods to Study Higher-Order Chromatin Organization.

Three-dimensional organization of the chromatin has important roles in transcription, replication, DNA repair, and pathologic events such as translocations. There are two fundamental ways to study higher-order chromatin organization: microscopic and molecular approaches. In this review, we briefly introduce the molecular approaches, focusing on chromosome conformation capture or "3C" technology and its derivatives, which can be used to probe chromatin folding at resolutions beyond that provided by microscopy techniques.

Cell type specific alterations in interchromosomal networks across the cell cycle.

The interchromosomal organization of a subset of human chromosomes (#1, 4, 11, 12, 16, 17, and 18) was examined in G1 and S phase of human WI38 lung fibroblast and MCF10A breast epithelial cells. Radial positioning of the chromosome territories (CTs) was independent of gene density, but size dependent. While no changes in radial positioning during the cell cycle were detected, there were stage-specific differences between cell types.

Gene density and chromosome territory shape.

Despite decades of study of chromosome territories (CT) in the interphase nucleus of mammalian cells, our understanding of the global shape and 3-D organization of the individual CT remains very limited. Past microscopic analysis of CT suggested that while many of the CT appear to be very regular ellipsoid-like shapes, there were also those with more irregular shapes. We have undertaken a comprehensive analysis to determine the degree of shape regularity of different CT.