RESUMO
MCF7 cells acquire estrogen-independent proliferation after long-term estrogen deprivation (LTED), which recapitulates endocrine therapy resistance. LTED cells can become primed for apoptosis, but the underlying mechanism is largely unknown. We previously reported that Eleanor non-coding RNAs (ncRNAs) upregulate the ESR1 gene in LTED cells. Here, we show that Eleanors delineate the topologically associating domain (TAD) of the ESR1 locus in the active nuclear compartment of LTED cells. The TAD interacts with another transcriptionally active TAD, which is 42.9 Mb away from ESR1 and contains a gene encoding the apoptotic transcription factor FOXO3. Inhibition of a promoter-associated Eleanor suppresses all genes inside the Eleanor TAD and the long-range interaction between the two TADs, but keeps FOXO3 active to facilitate apoptosis in LTED cells. These data indicate a role of ncRNAs in chromatin domain regulation, which may underlie the apoptosis-prone nature of therapy-resistant breast cancer cells and could be good therapeutic targets.
Assuntos
Apoptose/genética , Neoplasias da Mama/genética , Receptor alfa de Estrogênio/genética , Regulação Neoplásica da Expressão Gênica , RNA não Traduzido/metabolismo , Antineoplásicos Hormonais/farmacologia , Antineoplásicos Hormonais/uso terapêutico , Apoptose/efeitos dos fármacos , Inibidores da Aromatase/farmacologia , Inibidores da Aromatase/uso terapêutico , Sítios de Ligação/genética , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/patologia , Cromatina/genética , Cromatina/metabolismo , Resistencia a Medicamentos Antineoplásicos/genética , Epigênese Genética , Receptor alfa de Estrogênio/metabolismo , Estrogênios/metabolismo , Feminino , Proteína Forkhead Box O3/genética , Proteína Forkhead Box O3/metabolismo , Loci Gênicos/genética , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Células MCF-7 , Regiões Promotoras Genéticas/genética , Regulação para CimaRESUMO
Kinesin family member 4 (KIF4) and condensins I and II are essential chromosomal proteins for chromosome organization by locating primarily to the chromosome scaffold. However, the mechanism of how KIF4 and condensins localize to the chromosome scaffold is poorly understood. Here, we demonstrate a close relationship between the chromosome localization of KIF4 and condensin I, but not condensin II, and show that KIF4 and condensin I assist each other for stable scaffold formation by forming a stable complex. Moreover, phosphorylation of KIF4 and condensin I by Aurora B and polo-like kinase 1 (Plk1) is important for KIF4 and condensin I localization to the chromosome. Aurora B activity facilitates the targeting of KIF4 and condensin I to the chromosome, whereas Plk1 activity promotes the dissociation of these proteins from the chromosome. Thus, the interdependency between KIF4 and condensin I, and their phosphorylation states play important roles in chromosome scaffold organization during mitosis.
Assuntos
Adenosina Trifosfatases/metabolismo , Cromossomos Humanos , Proteínas de Ligação a DNA/metabolismo , Cinesinas/metabolismo , Complexos Multiproteicos/metabolismo , Aurora Quinase B/metabolismo , Células HeLa , Humanos , FosforilaçãoRESUMO
Chromosome higher order structure has been an enigma for over a century. The most important structural finding has been the presence of a chromosome scaffold composed of non-histone proteins; so-called scaffold proteins. However, the organization and function of the scaffold are still controversial. Here, we use three dimensional-structured illumination microscopy (3D-SIM) and focused ion beam/scanning electron microscopy (FIB/SEM) to reveal the axial distributions of scaffold proteins in metaphase chromosomes comprising two strands. We also find that scaffold protein can adaptably recover its original localization after chromosome reversion in the presence of cations. This reversion to the original morphology underscores the role of the scaffold for intrinsic structural integrity of chromosomes. We therefore propose a new structural model of the chromosome scaffold that includes twisted double strands, consistent with the physical properties of chromosomal bending flexibility and rigidity. Our model provides new insights into chromosome higher order structure.