Loss of Histone Locus Bodies in the Mature Hemocytes of Larval Lymph Gland Result in Hyperplasia of the Tissue in mxc Mutants of Drosophila

Mutations in the multi sex combs (mxc) gene in Drosophila results in malignant hyperplasia in larval hematopoietic tissues, called lymph glands (LG). mxc encodes a component of the histone locus body (HLB) that is essential for cell cycle-dependent transcription and processing of histone mRNAs. The mammalian nuclear protein ataxia-telangiectasia (NPAT) gene, encoded by the responsible gene for ataxia telangiectasia, is a functional Mxc orthologue. However, their roles in tumorigenesis are unclear. Genetic analyses of the mxc mutants and larvae having LG-specific depletion revealed that a reduced activity of the gene resulted in the hyperplasia, which is caused by hyper-proliferation of immature LG cells. The depletion of mxc in mature hemocytes of the LG resulted in the hyperplasia. Furthermore, the inhibition of HLB formation was required for LG hyperplasia. In the mutant larvae, the total mRNA levels of the five canonical histones decreased, and abnormal forms of polyadenylated histone mRNAs, detected rarely in normal larvae, were generated. The ectopic expression of the polyadenylated mRNAs was sufficient for the reproduction of the hyperplasia. The loss of HLB function, especially 3′-end processing of histone mRNAs, is critical for malignant LG hyperplasia in this leukemia model in Drosophila. We propose that mxc is involved in the activation to induce adenosine deaminase-related growth factor A (Adgf-A), which suppresses immature cell proliferation in LG.

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CDK-regulated phase separation seeded by histone genes ensures precise growth and function of Histone Locus Bodies

10.1101/789933 ◽

2019 ◽

Cited By ~ 2

Author(s):

Woonyung Hur ◽

Marco Tarzia ◽

Victoria E. Deneke ◽

Esteban A. Terzo ◽

Robert J. Duronio ◽

...

Keyword(s):

Phase Separation ◽

Gene Activation ◽

Nuclear Body ◽

Histone Mrnas ◽

Histone Locus Bodies ◽

Sex Combs ◽

Zygotic Gene ◽

Zygotic Gene Activation ◽

And Function ◽

Histone Locus

SummaryMany membrane-less organelles form through liquid-liquid phase separation, but how their size is controlled and whether size is linked to function remain poorly understood. The Histone Locus Body (HLB) is an evolutionarily conserved nuclear body that regulates the transcription and processing of histone mRNAs. Here, we show that Drosophila HLBs form through phase separation of the scaffold protein multi-sex combs (Mxc). The size of HLBs is controlled in a precise and dynamic manner that is dependent on the cell cycle and zygotic gene activation. Control of HLB growth is achieved by a mechanism integrating nascent mRNAs at the histone locus, which catalyzes phase separation, and the nuclear concentration of Mxc, which is controlled by the activity of cyclin-dependent kinases. Reduced Cdk2 activity results in smaller HLBs and the appearance of nascent, misprocessed histone mRNAs. Our experiments thus identify a mechanism linking nuclear body growth and size with gene expression.

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A region of SLBP outside the mRNA processing domain is essential for deposition of histone mRNA into the Drosophila egg

Journal of Cell Science ◽

10.1242/jcs.251728 ◽

2021 ◽

pp. jcs.251728

Author(s):

Jennifer Michelle Potter-Birriel ◽

Graydon B. Gonsalvez ◽

William F. Marzluff

Keyword(s):

Histone Gene ◽

Nuclear Localization Sequence ◽

Histone Genes ◽

High Concentration ◽

Histone Mrna ◽

Histone Mrnas ◽

Histone Locus Bodies ◽

Cellular Mrnas ◽

Localization Sequence ◽

Histone Locus

Replication-dependent histone mRNAs are the only cellular mRNAs that are not polyadenylated, ending in a stemloop instead of a polyA tail, and are normally regulated coordinately with DNA replication. SLBP binds the 3’ end of histone mRNA, and is required for processing and translation. During Drosophila oogenesis, large amounts of histone mRNAs and proteins are deposited in the developing oocyte.The maternally deposited histone mRNA is synthesized in stage 10B oocytes after the nurse cells complete endoreduplication. We report that in WT stage 10B oocytes, the Histone Locus Bodies (HLBs), formed on the histone genes, produce histone mRNAs in the absence of phosphorylation of Mxc, normally required for histone gene expression in S-phase cells. Two mutants of SLBP, one with reduced expression and another with a 10 aa deletion, fail to deposit sufficient histone mRNA in the oocyte, and don't transcribe the histone genes in stage 10B. Mutations in a putative SLBP nuclear localization sequence overlapping the deletion, phenocopy the deletion. We conclude a high concentration of SLBP in the nucleus of stage 10B oocytes is essential for histone gene transcription.

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A region of Drosophila SLBP distinct from the histone pre-mRNA binding and processing domains is essential for deposition of histone mRNA in the oocyte

10.1101/2020.04.16.030577 ◽

2020 ◽

Author(s):

Jennifer Potter-Birriel ◽

Graydon B. Gonsalvez ◽

William F. Marzluff

Keyword(s):

Embryonic Cell ◽

Histone Mrna ◽

Stem Loop ◽

Cell Cycles ◽

Histone Mrnas ◽

Histone Locus Bodies ◽

Cellular Mrnas ◽

Histone Locus ◽

Mrna Binding

ABSTRACTDuring Drosophila oogenesis, large amounts of histone mRNA and proteins are deposited in the developing oocyte. These are sufficient for the first 14 embryonic cell cycles and provide the developing embryo with sufficient histone proteins until the zygotic histone genes are activated. The maternally deposited histone mRNA is synthesized in stage 10b of oogenesis after completion of endoreduplication of the nurse cells. Histone mRNAs are the only cellular mRNAs that are not polyadenylated, ending instead in a conserved stemloop instead of a polyA tail. The Stem-loop binding protein (SLBP) binds the 3’ end of histone mRNA and is essential for both the biosynthesis and translation of histone mRNA. We report that a 10 aa region in SLBP, which is not required for processing in vitro, is essential for transcription of histone mRNA in the stage 10b oocyte. In stage 10b the Histone Locus Bodies (HLBs) produce histone mRNAs in the absence of phosphorylation of Mxc, normally required for histone gene expression in S-phase cells. Mutants expressing this SLBP develop normally, produce small amounts of polyadenylated histone mRNA throughout development, but little histone mRNA in stage 10b resulting in death of the embryos in the first hr of development.

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Identification of Keratin 23 as a Hepatitis C Virus-Induced Host Factor in the Human Liver

Cells ◽

10.3390/cells8060610 ◽

2019 ◽

Vol 8 (6) ◽

pp. 610 ◽

Cited By ~ 2

Author(s):

Volker Kinast ◽

Stefan L. Leber ◽

Richard J. P. Brown ◽

Gabrielle Vieyres ◽

Patrick Behrendt ◽

...

Keyword(s):

Hepatitis C Virus ◽

Liver Disease ◽

Hepatitis C ◽

Ectopic Expression ◽

Host Factor ◽

Hcv Infection ◽

Mrna Levels ◽

Structural Support ◽

Protein Levels ◽

Inducible Protein

Keratin proteins form intermediate filaments, which provide structural support for many tissues. Multiple keratin family members are reported to be associated with the progression of liver disease of multiple etiologies. For example, keratin 23 (KRT23) was reported as a stress-inducible protein, whose expression levels correlate with the severity of liver disease. Hepatitis C virus (HCV) is a human pathogen that causes chronic liver diseases including fibrosis, cirrhosis, and hepatocellular carcinoma. However, a link between KRT23 and hepatitis C virus (HCV) infection has not been reported previously. In this study, we investigated KRT23 mRNA levels in datasets from liver biopsies of chronic hepatitis C (CHC) patients and in primary human hepatocytes experimentally infected with HCV, in addition to hepatoma cells. Interestingly, in each of these specimens, we observed an HCV-dependent increase of mRNA levels. Importantly, the KRT23 protein levels in patient plasma decreased upon viral clearance. Ectopic expression of KRT23 enhanced HCV infection; however, CRIPSPR/Cas9-mediated knockout did not show altered replication efficiency. Taken together, our study identifies KRT23 as a novel, virus-induced host-factor for hepatitis C virus.

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Drosophila CG2469 Encodes a Homolog of Human CTR9 and Is Essential for Development

G3 Genes|Genome|Genetics ◽

10.1534/g3.116.035196 ◽

2016 ◽

Vol 6 (12) ◽

pp. 3849-3857 ◽

Cited By ~ 5

Author(s):

Dhananjay Chaturvedi ◽

Mayu Inaba ◽

Shane Scoggin ◽

Michael Buszczak

Keyword(s):

Germ Cell ◽

Sequence Similarity ◽

Cell Loss ◽

Germline Stem Cell ◽

Cell Nuclei ◽

Transcriptional Initiation ◽

Histone Locus Bodies ◽

Paf1 Complex ◽

Histone Locus ◽

Drosophila Cells

Abstract Conserved from yeast to humans, the Paf1 complex participates in a number of diverse processes including transcriptional initiation and polyadenylation. This complex typically includes five proteins: Paf1, Rtf1, Cdc73, Leo1, and Ctr9. Previous efforts identified clear Drosophila homologs of Paf1, Rtf1, and Cdc73 based on sequence similarity. Further work showed that these proteins help to regulate gene expression and are required for viability. To date, a Drosophila homolog of Ctr9 has remained uncharacterized. Here, we show that the gene CG2469 encodes a functional Drosophila Ctr9 homolog. Both human and Drosophila Ctr9 localize to the nuclei of Drosophila cells and appear enriched in histone locus bodies. RNAi knockdown of Drosophila Ctr9 results in a germline stem cell loss phenotype marked by defects in the morphology of germ cell nuclei. A molecular null mutation of Drosophila Ctr9 results in lethality and a human cDNA CTR9 transgene rescues this phenotype. Clonal analysis in the ovary using this null allele reveals that loss of Drosophila Ctr9 results in a reduction of global levels of histone H3 trimethylation of lysine 4 (H3K4me3), but does not compromise the maintenance of stem cells in ovaries. Given the differences between the null mutant and RNAi knockdown phenotypes, the germ cell defects caused by RNAi likely result from the combined loss of Drosophila Ctr9 and other unidentified genes. These data provide further evidence that the function of this Paf1 complex component is conserved across species.

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Ectopic expression of homeotic genes caused by the elimination of the Polycomb gene in Drosophila imaginal epidermis

Development ◽

10.1242/dev.104.4.713 ◽

1988 ◽

Vol 104 (4) ◽

pp. 713-720 ◽

Cited By ~ 19

Author(s):

A. Busturia ◽

G. Morata

Keyword(s):

Ectopic Expression ◽

Homeotic Genes ◽

Sex Combs Reduced ◽

Hierarchical Order ◽

Sex Combs ◽

Morphological Patterns

The morphological patterns in the adult cuticle of Drosophila are determined principally by the homeotic genes of the bithorax and Antennapedia complexes. We find that many of these genes become indiscriminately active in the adult epidermis when the Pc gene is eliminated. By using the Pc3 mutation and various BX-C mutant combinations, we have generated clones of imaginal cells possessing different combinations of active homeotic genes. We find that, in the absence of BX-C genes, Pc- clones develop prothoracic patterns; this is probably due to the activity of Sex combs reduced which overrules Antennapedia. Adding contributions of Ultrabithorax, abdominal-A and Abdominal-B results in thoracic or abdominal patterns. We have established a hierarchical order among these genes: Antp less than Scr less than Ubx less than abd-A less than Abd-B. In addition, we show that the engrailed gene is ectopically active in Pc- imaginal cells.

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Tumor-Suppressive MicroRNA-708 Targets Notch1 to Suppress Cell Proliferation and Invasion in Gastric Cancer

Oncology Research Featuring Preclinical and Clinical Cancer Therapeutics ◽

10.3727/096504018x15179680859017 ◽

2018 ◽

Vol 26 (9) ◽

pp. 1317-1326 ◽

Cited By ~ 4

Author(s):

Xuyan Li ◽

Xuanfang Zhong ◽

Xiuhua Pan ◽

Yan Ji

Keyword(s):

Gastric Cancer ◽

Cell Proliferation ◽

Quantitative Polymerase Chain Reaction ◽

Ectopic Expression ◽

Luciferase Reporter ◽

Mrna Levels ◽

Inverse Association ◽

Novel Target ◽

Cancer Tissues ◽

Proliferation And Invasion

Growing evidence has demonstrated that numerous microRNAs (miRNAs) may participate in the regulation of gastric carcinogenesis and progression. This phenomenon suggests that gastric cancer-related miRNAs can be identified as effective therapeutic targets for this disease. miRNA-708 (miR-708) has recently been reported to be aberrantly expressed in several types of cancer and contribute to carcinogenesis and progression. However, the expression level, biological roles, and underlying mechanisms of miR-708 in gastric cancer are poorly understood. Here we found that miR-708 was downregulated in gastric cancer tissues and cell lines. Downregulated miR-708 expression was significantly associated with lymphatic metastasis, invasive depth, and TNM stage. Further investigation indicated that ectopic expression of miR-708 prohibited cell proliferation and invasion in gastric cancer. Bioinformatics analysis showed that Notch1 was a potential target of miR-708. Notch1 was further confirmed as a direct target gene of miR-708 in gastric cancer by dual-luciferase reporter assay, reverse transcription quantitative polymerase chain reaction, and Western blot analysis. Furthermore, an inverse association was found between miR-708 and Notch1 mRNA levels in gastric cancer tissues. In addition, restored Notch1 expression rescued the inhibitory effects on gastric cancer cell proliferation and invasion induced by miR-708 overexpression. Our findings highlight the tumor-suppressive roles of miR-708 in gastric cancer and suggest that miR-708 may be investigated as a novel target for gastric cancer treatment.

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Needs and Targets for the multi sex combs Gene Product in Drosophila melanogaster

Genetics ◽

10.1093/genetics/149.4.1823 ◽

1998 ◽

Vol 149 (4) ◽

pp. 1823-1838 ◽

Cited By ~ 1

Author(s):

Olivier Saget ◽

Françoise Forquignon ◽

Pedro Santamaria ◽

Neel B Randsholt

Keyword(s):

Drosophila Melanogaster ◽

Ectopic Expression ◽

Polycomb Group ◽

Homeotic Genes ◽

Maternal Control ◽

Gap Gene ◽

Sex Combs ◽

Normal Expression ◽

Selector Genes ◽

Mutant Phenotypes

Abstract We have analyzed the requirements for the multi sex combs (mxc) gene during development to gain further insight into the mechanisms and developmental processes that depend on the important trans-regulators forming the Polycomb group (PcG) in Drosophila melanogaster. mxc is allelic with the tumor suppressor locus lethal (1) malignant blood neoplasm (l(1)mbn). We show that the mxc product is dramatically needed in most tissues because its loss leads to cell death after a few divisions. mxc has also a strong maternal effect. We find that hypomorphic mxc mutations enhance other PcG gene mutant phenotypes and cause ectopic expression of homeotic genes, confirming that PcG products are cooperatively involved in repression of selector genes outside their normal expression domains. We also demonstrate that the mxc product is needed for imaginal head specification, through regulation of the ANT-C gene Deformed. Our analysis reveals that mxc is involved in the maternal control of early zygotic gap gene expression previously reported for some PcG genes and suggests that the mechanism of this early PcG function could be different from the PcG-mediated regulation of homeotic selector genes later in development. We discuss these data in view of the numerous functions of PcG genes during development.

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