scholarly journals Common Fragile Site Profiling in Epithelial and Erythroid Cells Reveals that Most Recurrent Cancer Deletions Lie in Fragile Sites Hosting Large Genes

Cell Reports ◽  
2013 ◽  
Vol 4 (3) ◽  
pp. 420-428 ◽  
Author(s):  
Benoît Le Tallec ◽  
Gaël Armel Millot ◽  
Marion Esther Blin ◽  
Olivier Brison ◽  
Bernard Dutrillaux ◽  
...  
Keyword(s):  
Fragile Site ◽  
Fragile Sites ◽  
Common Fragile Site ◽  
Erythroid Cells ◽  
Recurrent Cancer ◽  
Large Genes

scholarly journals FANCD2 tunes the UPR preventing mitochondrial stress-­induced common fragile site instability

2019 ◽  
Author(s):  
Philippe Fernandes ◽  
Benoit Miotto ◽  
Claude Saint-Ruf ◽  
Viola Nähse ◽  
Silvia Ravera ◽  
...  
Keyword(s):  
Gene Expression ◽  
Genome Instability ◽  
Fragile Site ◽  
Transcriptional Response ◽  
Genomic Analysis ◽  
Fragile Sites ◽  
The Unfolded Protein Response ◽  
And Function ◽  
Large Genes ◽  
Genomic Regions

AbstractCommon fragile sites (CFSs) are genomic regions frequently involved in cancer-associated rearrangements. Most CFSs lie within large genes, and their instability relies on transcription- and replication-dependent mechanisms. Here, we uncover a role for the UBL5-dependent branch of the unfolded protein response pathway (UPR) in the maintenance of CFS stability. We show that genetic or pharmacological UPR activation induces CFS gene expression and concomitant relocalization of FANCD2, a master regulator of CFS stability, to CFSs. Furthermore, a genomic analysis of FANCD2 binding sites identified an enrichment for mitochondrial UPR transcriptional response elements in FANCD2 bound regions. We demonstrated that depletion of FANCD2 increases CFS gene transcription and their instability while also inducing mitochondrial dysfunction and triggering the activation of the UPR pathway. Depletion of UBL5, a mediator of the UPR, but not ATF4, reduces CFS gene expression and breakage in FANCD2-depleted cells. We thus demonstrate that FANCD2 recruitment and function at CFSs depends on transcription and UPR signaling, and in absence of transcription or UBL5, FANCD2 is dispensable for CFS stability. We propose that FANCD2 coordinates nuclear and mitochondrial activities by tuning the UPR to prevent genome instability.

scholarly journals BRCA1 Is Required for Common-Fragile-Site Stability via Its G2/M Checkpoint Function

2004 ◽  
Vol 24 (15) ◽  
pp. 6701-6709 ◽  
Author(s):  
Martin F. Arlt ◽  
Bo Xu ◽  
Sandra G. Durkin ◽  
Anne M. Casper ◽  
Michael B. Kastan ◽  
...  
Keyword(s):  
Rna Interference ◽  
Tumor Suppressor ◽  
Dna Synthesis ◽  
Cancer Cells ◽  
Tumor Suppressor Genes ◽  
Fragile Site ◽  
Fragile Sites ◽  
Common Fragile Site ◽  
Interacting Proteins ◽  
Checkpoint Pathway

ABSTRACT Common fragile sites are loci that form chromosome gaps or breaks when DNA synthesis is partially inhibited. Fragile sites are prone to deletions, translocations, and other rearrangements that can cause the inactivation of associated tumor suppressor genes in cancer cells. It was previously shown that ATR is critical to fragile-site stability and that ATR-deficient cells have greatly elevated fragile-site expression (A. M. Casper, P. Nghiem, M. F. Arlt, and T. W. Glover, Cell 111:779-789, 2002). Here we demonstrate that mouse and human cells deficient for BRCA1, due to mutation or knockdown by RNA interference, also have elevated fragile-site expression. We further show that BRCA1 functions in the induction of the G2/M checkpoint after aphidicolin-induced replication stalling and that this checkpoint function is involved in fragile-site stability. These data indicate that BRCA1 is important in fragile-site stability and that fragile sites are recognized by the G2/M checkpoint pathway, in which BRCA1 plays a key role. Furthermore, they suggest that mutations in BRCA1 or interacting proteins could lead to rearrangements at fragile sites in cancer cells.

Abnormalities of 16q in Multiple Myeloma Are Associated with Poor Prognosis: 500K Gene Mapping and Expression Correlations Identify Two Potential Tumor Suppressor Genes, WWOX and CYLD.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 110-110
Author(s):  
Matthew W. Jenner ◽  
Paola E. Leone ◽  
Brian A. Walker ◽  
David C. Johnson ◽  
Laura Chiecchio ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Gene Mapping ◽  
Tumor Suppressor Genes ◽  
Poor Prognosis ◽  
Fragile Site ◽  
Fragile Sites ◽  
Common Fragile Site ◽  
Chromosome 16 ◽  
Common Fragile Sites ◽  
Potential Tumor Suppressor

Abstract Abnormalities of 16q are important recurrent events in multiple myeloma (MM). We performed FISH on CD138 selected plasma cells from 701 newly diagnosed MM patients from the LRF UKMF cytogenetics database. Gene mapping, including paired normal controls, and gene expression analysis was performed on 55 cases using the Affymetrix Human Mapping 500K Array Set and U133 Plus 2.0 Arrays respectively. 16q deletion (del16q) was identified by FISH using probes for cMAF (Abbott Diagnostics) in 131/701 cases (18.7%) and was significantly associated with deletion 17p (16.5% vs. 8.9%, p=0.006), deletion 13 (60.8% vs. 48.5%, p=0.009), deletion of IgH (22.1% vs. 11.1%, p=0.0003) and non-hyperdiploid status (58.3% vs. 42.7%, p=0.006). Del16q showed a trend to poor overall survival, mean survival 43 vs. 61 months (p=0.09), and was associated with significantly worse survival in combination with t(4;14) compared with either t(4;14) or del16q alone, mean survival 15 vs. 26 vs. 45 months respectively (p=0.006). t(14;16) was identified by FISH in 31/701 cases (4.4%) and was associated with poor prognosis, mean survival 29 vs. 54 months (p=0.005). Mapping arrays revealed loss of heterozygosity (LOH) involving all or part of 16q in 20 of 55 cases (36%) in 3 distinct patterns: uniparental disomy (UPD) of chromosome 16 or 16q in 4/55 cases (7%); deletion of chromosome 16 or the whole of 16q in 11/55 cases (20%); and interstitial deletion of small regions of 16q in 5/55 cases (10%), focused on 16q12, the location of CYLD, and 16q23, the location of WWOX. 16q LOH was distributed across translocation groups but was identified in all 4 mapping cases containing 17p deletion, supporting the association identified by FISH. As WWOX is the site of the common fragile site FRA16D and deletions at common fragile sites have been associated with DNA instability in human cancers, we assessed this using gene mapping in these 55 MM cases. Although deletions spanning other common fragile sites were identified, they were not restricted to those with 16q LOH. However, in 2 t(14;16) cases, hemizygous deletions of approximately 100kb could be identified within WWOX at the presumed translocation breakpoint. One of the t(14;16) cases had a similar hemizygous deletion within FHIT, another tumor suppressor gene located within common fragile site FRA3B, consistent with findings in other cancer types. Cases with 16q LOH or t(14;16) all had significantly reduced WWOX expression relative to cases without 16q abnormalities, confirming gene inactivation by either LOH or translocation. Cases with 16q LOH also had significantly reduced expression of two other potential tumor suppressor genes located on 16q, CYLD and RBL2. In summary, our data confirms the adverse prognosis associated with 16q translocation or deletion. Array data reveals 16q LOH occurs due to deletion or UPD with two regions involved, one defined by CYLD and the other by WWOX. WWOX is also inactivated by translocation and is associated with interstitial deletions at this and other common fragile sites. WWOX is a likely candidate gene in MM pathogenesis because of its interaction with TP53 and CYLD via its effects on NF-κB.

scholarly journals Replication Delay along FRA7H, a Common Fragile Site on Human Chromosome 7, Leads to Chromosomal Instability

2000 ◽  
Vol 20 (12) ◽  
pp. 4420-4427 ◽  
Author(s):  
Asaf Hellman ◽  
Ayelet Rahat ◽  
Stephen W. Scherer ◽  
Ariel Darvasi ◽  
Lap-Chee Tsui ◽  
...  
Keyword(s):  
Chromosomal Instability ◽  
Fragile Site ◽  
S Phase ◽  
Fragile Sites ◽  
Common Fragile Site ◽  
Replication Pattern ◽  
Replication Time ◽  
The Common ◽  
Human Chromosome 7

ABSTRACT Common fragile sites are specific chromosomal loci that show gaps, breaks, or rearrangements in metaphase chromosomes under conditions that interfere with DNA replication. The mechanism underlying the chromosomal instability at fragile sites was hypothesized to associate with late replication time. Here, we aimed to investigate the replication pattern of the common fragile site FRA7H, encompassing 160 kb on the long arm of human chromosome 7. Using in situ hybridization on interphase nuclei, we revealed that the replication of this region is initiated relatively early, before 30% of S phase is completed. However, a high fraction (∼35%) of S-phase nuclei showed allelic asynchrony, indicating that the replication of FRA7H is accomplished at different times in S phase. This allelic asynchrony is not the result of a specific replication time of each FRA7H allele. Analysis of the replication pattern of adjacent clones along FRA7H by using cell population and two-color fluorescent in situ hybridization analyses showed significant differences in the replication of adjacent clones, under normal growth condition and upon aphidicolin treatment. This pattern significantly differed from that of two nonfragile regions which showed a coordinated replication under both conditions. These results indicate that aphidicolin is enhancing an already existing difference in the replication time along the FRA7H region. Based on our replication analysis of FRA7H and on previous analysis of the common fragile site FRA3B, we suggest that delayed replication is underlying the fragility at aphidicolin-induced common fragile sites.

scholarly journals Large Intronic Deletion of the Fragile Site Gene PRKN Dramatically Lowers Its Fragility Without Impacting Gene Expression

2021 ◽  
Vol 12 ◽  
Author(s):  
Sebastian H. N. Munk ◽  
Vasileios Voutsinos ◽  
Vibe H. Oestergaard
Keyword(s):  
Gene Expression ◽  
Reverse Genetics ◽  
Fragile Site ◽  
Fragile Sites ◽  
Metaphase Chromosomes ◽  
Large Gene ◽  
Large Intron ◽  
Chromosomal Fragile Sites ◽  
Large Genes ◽  
Genomic Regions

Common chromosomal fragile sites (CFSs) are genomic regions prone to form breaks and gaps on metaphase chromosomes during conditions of replication stress. Moreover, CFSs are hotspots for deletions and amplifications in cancer genomes. Fragility at CFSs is caused by transcription of extremely large genes, which contributes to replication problems. These extremely large genes do not encode large proteins, but the extreme sizes of the genes originate from vast introns. Intriguingly, the intron sizes of extremely large genes are conserved between mammals and birds. Here, we have used reverse genetics to address the function and significance of the largest intron in the extremely large gene PRKN, which is highly fragile in our model system. Specifically, we have introduced an 80-kilobase deletion in intron 7 of PRKN. We find that gene expression of PRKN is largely unaffected by this intronic deletion. Strikingly, the intronic deletion, which leads to a 12% reduction of the overall size of the PRKN gene body, results in an almost twofold reduction of the PRKN fragility. Our results stress that while the large intron clearly contributes to the fragility of PRKN, it does not play an important role for PRKN expression. Taken together, our findings further add to the mystery concerning conservation of the seemingly non-functional but troublesome large introns in PRKN.

scholarly journals FANCD2 modulates the mitochondrial stress response to prevent common fragile site instability

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Philippe Fernandes ◽  
Benoit Miotto ◽  
Claude Saint-Ruf ◽  
Maha Said ◽  
Viviana Barra ◽  
...  
Keyword(s):  
Stress Response ◽  
Genome Instability ◽  
Fragile Site ◽  
Fragile Sites ◽  
Human Cells ◽  
Mitochondrial Stress ◽  
Stress Response Pathway ◽  
Stress Dependent ◽  
Large Genes ◽  
Genomic Regions

AbstractCommon fragile sites (CFSs) are genomic regions frequently involved in cancer-associated rearrangements. Most CFSs lie within large genes, and their instability involves transcription- and replication-dependent mechanisms. Here, we uncover a role for the mitochondrial stress response pathway in the regulation of CFS stability in human cells. We show that FANCD2, a master regulator of CFS stability, dampens the activation of the mitochondrial stress response and prevents mitochondrial dysfunction. Genetic or pharmacological activation of mitochondrial stress signaling induces CFS gene expression and concomitant relocalization to CFSs of FANCD2. FANCD2 attenuates CFS gene transcription and promotes CFS gene stability. Mechanistically, we demonstrate that the mitochondrial stress-dependent induction of CFS genes is mediated by ubiquitin-like protein 5 (UBL5), and that a UBL5-FANCD2 dependent axis regulates the mitochondrial UPR in human cells. We propose that FANCD2 coordinates nuclear and mitochondrial activities to prevent genome instability.

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