R-loops are three-stranded nucleic acid structures composed of an RNA:DNA hybrid and displaced DNA strand. These structures can halt DNA replication when formed co-transcriptionally in the opposite orientation to replication fork progression. A recent study has shown that replication forks stalled by co-transcriptional R-loops can be restarted by a mechanism involving fork cleavage by MUS81 endonuclease, followed by ELL-dependent reactivation of transcription, and fork religation by the DNA ligase IV (LIG4)/XRCC4 complex. However, how R-loops are eliminated to allow the sequential restart of transcription and replication in this pathway remains elusive. Here, we identified the human DDX17 helicase as a factor that associates with R-loops and counteracts R-loop-mediated replication stress to preserve genome stability. We show that DDX17 unwinds R-loops in vitro and promotes MUS81-dependent restart of R-loop-stalled forks in human cells in a manner dependent on its helicase activity. Loss of DDX17 helicase induces accumulation of R-loops and the formation of R-loop-dependent anaphase bridges and micronuclei. These findings establish DDX17 as a component of the MUS81-LIG4-ELL pathway for resolution of R-loop-mediated transcription-replication conflicts, which may be involved in R-loop unwinding.
RNA interference (RNAi) designates sequence-specific mRNA degradation mediated by small RNAs generated from long double-stranded RNA (dsRNA) by RNase III Dicer. RNAi appears inactive in mammalian cells except for mouse oocytes, where high RNAi activity exists because of an N-terminally truncated Dicer isoform, denoted DicerO. DicerO processes dsRNA into small RNAs more efficiently than the full-length Dicer expressed in somatic cells. DicerO is expressed from an oocyte-specific promoter of retrotransposon origin, which is silenced in other cell types. In this work, we evaluated CRISPR-based strategies for epigenetic targeting of the endogenous Dicer gene to restore DicerO expression and, consequently, RNAi. We show that reactivation of DicerO expression can be achieved in mouse embryonic stem cells, but it is not sufficient to establish a robust canonical RNAi response.
- MeSH
- buňky 3T3 MeSH
- DEAD-box RNA-helikasy antagonisté a inhibitory genetika MeSH
- embryonální kmenové buňky cytologie metabolismus MeSH
- malá interferující RNA genetika MeSH
- myši MeSH
- promotorové oblasti (genetika) * MeSH
- ribonukleasa III antagonisté a inhibitory genetika MeSH
- RNA interference MeSH
- sekvence CRISPR * MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
MicroRNAs (miRNAs) are ubiquitous small RNAs guiding post-transcriptional gene repression in countless biological processes. However, the miRNA pathway in mouse oocytes appears inactive and dispensable for development. We propose that marginalization of the miRNA pathway activity stems from the constraints and adaptations of RNA metabolism elicited by the diluting effects of oocyte growth. We report that miRNAs do not accumulate like mRNAs during the oocyte growth because miRNA turnover has not adapted to it. The most abundant miRNAs total tens of thousands of molecules in growing (∅ 40 μm) and fully grown (∅ 80 μm) oocytes, a number similar to that observed in much smaller fibroblasts. The lack of miRNA accumulation results in a 100-fold lower miRNA concentration in fully grown oocytes than in somatic cells. This brings a knock-down-like effect, where diluted miRNAs engage targets but are not abundant enough for significant repression. Low-miRNA concentrations were observed in rat, hamster, porcine and bovine oocytes, arguing that miRNA inactivity is not mouse-specific but a common mammalian oocyte feature. Injection of 250,000 miRNA molecules was sufficient to restore reporter repression in mouse and porcine oocytes, suggesting that miRNA inactivity comes from low-miRNA abundance and not from some suppressor of the pathway.
- MeSH
- buňky 3T3 MeSH
- druhová specificita MeSH
- křečci praví MeSH
- krysa rodu rattus MeSH
- kultivované buňky MeSH
- messenger RNA genetika metabolismus MeSH
- mikro RNA genetika metabolismus MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- oocyty cytologie metabolismus MeSH
- oogeneze * MeSH
- prasata MeSH
- skot MeSH
- teoretické modely MeSH
- vývojová regulace genové exprese MeSH
- zvířata MeSH
- Check Tag
- křečci praví MeSH
- krysa rodu rattus MeSH
- myši MeSH
- skot MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Carbonic anhydrase IX (CA IX) is a transmembrane enzyme overexpressed in hypoxic tumors, where it plays an important role in tumor progression. Specific CA IX inhibitors potentially could serve as anti-cancer drugs. We designed a series of sulfonamide inhibitors containing carborane clusters based on prior structural knowledge of carborane binding into the enzyme active site. Two types of carborane clusters, 12-vertex dicarba-closo-dodecaborane and 11-vertex 7,8-dicarba-nido-undecaborate (dicarbollide), were connected to a sulfonamide moiety via aliphatic linkers of varying lengths (1-4 carbon atoms; n = 1-4). In vitro testing of CA inhibitory potencies revealed that the optimal linker length for selective inhibition of CA IX was n = 3. A 1-sulfamidopropyl-1,2-dicarba-closo-dodecaborane (3) emerged as the strongest CA IX inhibitor from this series, with a Ki value of 0.5 nM and roughly 1230-fold selectivity towards CA IX over CA II. X-ray studies of 3 yielded structural insights into their binding modes within the CA IX active site. Compound 3 exhibited moderate cytotoxicity against cancer cell lines and primary cell lines in 2D cultures. Cytotoxicity towards multicellular spheroids was also observed. Moreover, 3 significantly lowered the amount of CA IX on the cell surface both in 2D cultures and spheroids and facilitated penetration of doxorubicin. Although 3 had only a moderate effect on tumor size in mice, we observed favorable ADME properties and pharmacokinetics in mice, and preferential presence in brain over serum.
- MeSH
- antigeny nádorové metabolismus MeSH
- antitumorózní látky chemická syntéza chemie farmakologie MeSH
- experimentální nádory farmakoterapie metabolismus MeSH
- inhibitory karboanhydras chemická syntéza chemie farmakologie MeSH
- karboanhydrasa IX antagonisté a inhibitory metabolismus MeSH
- kultivované buňky MeSH
- léky antitumorózní - screeningové testy MeSH
- lidé MeSH
- molekulární struktura MeSH
- myši inbrední BALB C MeSH
- myši SCID MeSH
- myši MeSH
- nádory prsu farmakoterapie metabolismus MeSH
- proliferace buněk účinky léků MeSH
- psi MeSH
- rekombinantní proteiny metabolismus MeSH
- sulfonamidy chemická syntéza chemie farmakologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- psi MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
The first step in the development of human colorectal cancer is aberrant activation of the Wnt signaling pathway. Wnt signaling hyperactivation is predominantly caused by loss-of-function mutations in the adenomatous polyposis coli (APC) gene that encodes the pathway negative regulator. In order to identify genes affected by the Apc loss, we performed expression profiling of intestinal epithelium isolated from mice harboring a conditional Apc allele. The gene encoding transcriptional factor msh homeobox 1 (Msx1) displayed robust upregulation upon Apc inactivation. Histological analysis of the Apc-deficient epithelium revealed that in the small intestine, the Msx1 protein was localized exclusively in ectopic crypts, i.e., in pockets of proliferating cells abnormally positioned on the villi. Ablation of the Msx1 gene leads to the disappearance of ectopic crypts and loss of differentiated cells. Moreover, tumors arising from Msx1-deficient cells display altered morphology reminiscent of villous adenomas. In human tumor specimens, MSX1 displayed significantly increased expression in colonic neoplasia with a descending tendency during the lesion progression towards colorectal carcinoma. In summary, the results indicate that Msx1 represents a novel marker of intestinal tumorigenesis. In addition, we described the previously unknown relationship between the Msx1-dependent formation of ectopic crypts and cell differentiation.
- MeSH
- beta-katenin metabolismus MeSH
- buněčná diferenciace MeSH
- kolorektální nádory genetika patologie MeSH
- lidé MeSH
- myši knockoutované MeSH
- nádory tračníku genetika patologie MeSH
- protein familiární adenomatózní polypózy genetika metabolismus MeSH
- regulace genové exprese u nádorů MeSH
- signální dráha Wnt MeSH
- stanovení celkové genové exprese MeSH
- střevní sliznice metabolismus patologie MeSH
- tenké střevo patologie MeSH
- transkripční faktor MSX1 genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
γ-Tubulin is essential for microtubule nucleation and also plays less understood roles in nuclear and cell-cycle-related functions. High abundancy of γ-tubulin in acentrosomal Arabidopsis cells facilitated purification and biochemical characterization of large molecular species of γ-tubulin. TEM, fluorescence, and atomic force microscopy of purified high molecular γ-tubulin forms revealed the presence of linear filaments with a double protofilament substructure, filament bundles and aggregates. Filament formation from highly purified γ-tubulin free of γ-tubulin complex proteins (GCPs) was demonstrated for both plant and human γ-tubulin. Moreover, γ-tubulin associated with porcine brain microtubules formed oligomers. Experimental evidence on the intrinsic ability of γ-tubulin to oligomerize/polymerize was supported by conservation of α- and β-tubulin interfaces for longitudinal and lateral interactions for γ-tubulins. STED (stimulated emission depletion) microscopy of Arabidopsis cells revealed fine, short γ-tubulin fibrillar structures enriched on mitotic microtubular arrays that accumulated at polar regions of acentrosomal spindles and the outer nuclear envelope before mitosis, and were also present in nuclei. Fine fibrillar structures of γ-tubulin representing assemblies of higher order were localized in cell-cycle-dependent manner at sites of dispersed γ-tubulin location in acentrosomal plant cells as well as at sites of local γ-tubulin enrichment after drug treatment. Our findings that γ-tubulin preserves the capability of prokaryotic tubulins to self-organize into filaments assembling by lateral interaction into bundles/clusters help understanding of the relationship between structure and multiple cellular functions of this protein species and suggest that besides microtubule nucleation and organization, γ-tubulin may also have scaffolding or sequestration functions.
- MeSH
- Arabidopsis chemie genetika MeSH
- cytoskelet chemie genetika MeSH
- mikrofilamenta chemie genetika ultrastruktura MeSH
- mikrotubuly chemie genetika MeSH
- mitóza genetika MeSH
- polymerizace MeSH
- proteinové agregáty genetika MeSH
- proteiny asociované s mikrotubuly chemie genetika MeSH
- tubulin chemie genetika ultrastruktura MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
