FLASH is essential during early embryogenesis and cooperates with p73 to regulate histone gene transcription

Cola, Antonella De; Bongiorno-Borbone, Lucilla; Bianchi, Enrica; Barcaroli, Daniela; Carletti, Erminia; Knight, Richard; Ilio, Carmine Di; Melino, Gerry; Sette, Claudio; Laurenzi, Vincenzo De

doi:10.1038/onc.2011.274

Cited by 27 publications

(24 citation statements)

References 41 publications

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“…Our ChIP data, as well as the published literature, indicate that selected HLB components bind to both 5= and 3= regions of the histone H4 locus (2,14,28,58) (Fig. 6 and data not shown), thus potentially permitting a looped chromatin configuration that supports the rapid induction of histone gene expression at the G 1 /S-phase transition in both human embryonic stem cells and induced pluripotent stem cells.…”

Section: Discussionmentioning

confidence: 77%

“…Thus, dynamic G 1 /S-phase-related changes in protein-DNA interactions that occur within an intricate mireplication-dependent histones colocalize to specific subnuclear foci known as histone locus bodies (HLBs) (21,22). FLASH protein also localizes to HLBs (7,23), is required for transcription and 3=-end processing of histone mRNAs (2,14,28,58), and interacts with histone gene loci (Fig. 6B and data not shown).…”

Section: Resultsmentioning

confidence: 99%

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Epigenetic Control of Cell Cycle-Dependent Histone Gene Expression Is a Principal Component of the Abbreviated Pluripotent Cell Cycle

Medina

Ghule

Cruzat

et al. 2012

Molecular and Cellular Biology

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c Self-renewal of human pluripotent embryonic stem cells proceeds via an abbreviated cell cycle with a shortened G 1 phase. We examined which genes are modulated in this abbreviated period and the epigenetic mechanisms that control their expression. Accelerated upregulation of genes encoding histone proteins that support DNA replication is the most prominent gene regulatory program at the G 1 /S-phase transition in pluripotent cells. Expedited expression of histone genes is mediated by a unique chromatin architecture reflected by major nuclease hypersensitive sites, atypical distribution of epigenetic histone marks, and a region devoid of histone octamers. We observed remarkable differences in chromatin structure-hypersensitivity and histone protein modifications-between human embryonic stem (hES) and normal diploid cells. Cell cycle-dependent transcription factor binding permits dynamic three-dimensional interactions between transcript initiating and processing factors at 5= and 3= regions of the gene. Thus, progression through the abbreviated G 1 phase involves cell cycle stage-specific chromatin-remodeling events and rapid assembly of subnuclear microenvironments that activate histone gene transcription to promote nucleosomal packaging of newly replicated DNA during stem cell renewal. Human embryonic stem (hES) and induced pluripotent stem (iPS) cells maintain an undifferentiated state, are competent to proliferate indefinitely, and possess the ability to differentiate to all three germ layers (25,33,42,45,51,52,54,60). The unique ability to self-renew and to give rise to any cell type of an organism reflects the therapeutic potential of pluripotent stem cells in regenerative medicine. Human ES and iPS cells have an abbreviated G 1 phase and lack a classical restriction (R) point that normally controls commitment for progression into S phase (3,4,23,24). In contrast, proliferation of somatic cells is linked to growth factor-dependent passage through the R point in G 1 phase (43,44). The precise mechanisms by which cell cycle kinetics are modulated as cells switch between pluripotent and phenotype-committed states are complex and remain to be established. Key cell cyclerelated gene-activating events that occur between mitosis and S phase must be accelerated in the pluripotent state relative to those in phenotype-committed cells. More importantly, the absence of an R point in pluripotent cells necessitates reliance on other G 1 /Sphase-related gene-regulatory mechanisms to control entry into S phase. To understand molecular events at the G 1 /S-phase transition in pluripotent embryonic stem cells, it is necessary to identify genes that can be mechanistically examined for chromatin remodeling that accompanies gene activation.There are fundamental architectural modifications in genome configurations during the abbreviated self-renewal cell cycle of pluripotent hES cells to establish competency for DNA replication. As hES cells exit mitosis during self-renewal, chromosome decondensation and immediate assembly of c...

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Section: Discussionmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Epigenetic Control of Cell Cycle-Dependent Histone Gene Expression Is a Principal Component of the Abbreviated Pluripotent Cell Cycle

Medina

Ghule

Cruzat

et al. 2012

Molecular and Cellular Biology

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“…Null mutations of core HLB components (e.g., FLASH and NPAT/Mxc) in mammals and flies are lethal early in development, 35,36,117 likely in large part because little to no histone gene expression occurs. Because proteins like NPAT/Mxc and FLASH are necessary to scaffold HLB assembly and to stimulate histone mRNA biosynthesis, both of these functions will be lost in the absence of these proteins making it difficult to assign functional roles to HLB assembly per se.…”

Section: Discussionmentioning

confidence: 99%

Coordinating cell cycle-regulated histone gene expression through assembly and function of the Histone Locus Body

2017

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Metazoan replication-dependent (RD) histone genes encode the only known cellular mRNAs that are not polyadenylated. These mRNAs end instead in a conserved stem-loop, which is formed by an endonucleolytic cleavage of the pre-mRNA. The genes for all 5 histone proteins are clustered in all metazoans and coordinately regulated with high levels of expression during S phase. Production of histone mRNAs occurs in a nuclear body called the Histone Locus Body (HLB), a subdomain of the nucleus defined by a concentration of factors necessary for histone gene transcription and premRNA processing. These factors include the scaffolding protein NPAT, essential for histone gene transcription, and FLASH and U7 snRNP, both essential for histone pre-mRNA processing. Histone gene expression is activated by Cyclin E/Cdk2-mediated phosphorylation of NPAT at the G1-S transition. The concentration of factors within the HLB couples transcription with pre-mRNA processing, enhancing the efficiency of histone mRNA biosynthesis. KEYWORDSCell cycle; Drosophila; histone genes; mRNA processing; nuclear bodyProper utilization of genetic information in eukaryotes requires extensive three-dimensional organization of the genome and its associated proteins within the nucleus. The basic unit of genome organization is the nucleosome, an octamer of two molecules of each of the four core histone proteins (H2A, H2B, H3 and H4) that packages »147 base pairs of DNA. In mammalian cells, approximately 4£10 8 molcules of each core histone must be synthesized during S phase of the cell cycle to package the newly replicated DNA. Defects in this process result in genome instability that can contribute to human pathologies like cancer. Histone protein synthesis results from a large increase in production at the beginning of S phase of equal amounts of mRNAs encoding the four core nucleosomal histones, as well as histone H1. This highly coordinated gene expression event is performed by a set of transcription and pre-mRNA processing factors unique to replication dependent (RD) histone mRNA biosynthesis that assemble into a nuclear body tightly associated with RD histone genes called the histone locus body (HLB). HLB formation involves a combination of ordered and stochastic assembly steps, and cell cycle regulated changes in the HLB occur to activate histone gene expression during S phase. Here we describe the history of how the HLB was discovered followed by a discussion of HLB assembly mechanism and how the HLB functions in RD histone mRNA biosynthesis.

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“…This region interacts with the N-terminal region of FLASH (26), a 220-kDa protein that localizes to histone locus bodies and is required for histone gene expression (27,28) and transcriptional regulation of several essential genes, including oncogenes (29). Intriguingly, FLASH was initially discovered as a factor involved in Fas-mediated activation of caspase 8 (30).…”

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confidence: 99%

A Complex Containing the CPSF73 Endonuclease and Other Polyadenylation Factors Associates with U7 snRNP and Is Recruited to Histone Pre-mRNA for 3′-End Processing

Yang

Sabath

Dębski

et al. 2013

Molecular and Cellular Biology

112

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Animal replication-dependent histone pre-mRNAs are processed at the 3= end by endonucleolytic cleavage that is not followed by polyadenylation. The cleavage reaction is catalyzed by CPSF73 and depends on the U7 snRNP and its integral component, Lsm11. A critical role is also played by the 220-kDa protein FLASH, which interacts with Lsm11. Here we demonstrate that the N-terminal regions of these two proteins form a platform that tightly interacts with a unique combination of polyadenylation factors: symplekin, CstF64, and all CPSF subunits, including the endonuclease CPSF73. The interaction is inhibited by alterations in each component of the FLASH/Lsm11 complex, including point mutations in FLASH that are detrimental for processing. The same polyadenylation factors are associated with the endogenous U7 snRNP and are recruited in a U7-dependent manner to histone pre-mRNA. Collectively, our studies identify the molecular mechanism that recruits the CPSF73 endonuclease to histone pre-mRNAs, reveal an unexpected complexity of the U7 snRNP, and suggest that in animal cells polyadenylation factors assemble into two alternative complexes-one specifically crafted to generate polyadenylated mRNAs and the other to generate nonpolyadenylated histone mRNAs that end with the stem-loop.T he vast majority of eukaryotic pre-mRNAs are processed at the 3= end by cleavage coupled to polyadenylation (1-4). In this reaction, pre-mRNAs are cleaved 15 to 30 nucleotides after the highly conserved AAUAAA sequences and the upstream cleavage product is extended by addition of a poly(A) tail. Cleavage coupled to polyadenylation is carried out by a macromolecular machinery consisting of multiple proteins that assemble into at least four separate subcomplexes or factors. The AAUAAA sequence is recognized by cleavage and polyadenylation specificity factor (CPSF), which contains CPSF160, CPSF100, CPSF73, CPSF30, Fip1 (5), and the recently identified WDR33 (6). CPSF160 directly contacts the AAUAAA hexanucleotide, whereas CPSF73 is the endonuclease that catalyzes the cleavage reaction (7). Cleavage stimulation factor (CstF), consisting of CstF77, CstF64, and CstF50, recognizes the GU-rich sequence located downstream of the cleavage site. CstF64 makes direct contacts with this sequence and also interacts with CstF77, which in turn interacts with CstF50 (8). 3=-end processing by cleavage and polyadenylation additionally requires cleavage factor (CF) I m , consisting of 25-kDa and 68-kDa subunits (9), and cleavage factor II m containing at least two subunits, Pcf11 and Clp1 (2, 10). Individual components of the cleavage and polyadenylation machinery are connected with each other through a dense network of protein-protein interactions that stabilizes the entire complex and juxtaposes CPSF73 with the cleavage site. An important role in forming this network is played by symplekin, a protein that interacts with a number of polyadenylation factors and likely functions as a scaffold in 3=-end processing (8,11,12) and other processes, including cytoplasmi...

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FLASH is essential during early embryogenesis and cooperates with p73 to regulate histone gene transcription

Cited by 27 publications

References 41 publications

Epigenetic Control of Cell Cycle-Dependent Histone Gene Expression Is a Principal Component of the Abbreviated Pluripotent Cell Cycle

Epigenetic Control of Cell Cycle-Dependent Histone Gene Expression Is a Principal Component of the Abbreviated Pluripotent Cell Cycle

Coordinating cell cycle-regulated histone gene expression through assembly and function of the Histone Locus Body

A Complex Containing the CPSF73 Endonuclease and Other Polyadenylation Factors Associates with U7 snRNP and Is Recruited to Histone Pre-mRNA for 3′-End Processing

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