Werner syndrome helicase modulates G4 DNA-dependent transcription and opposes mechanistically distinct senescence-associated gene expression programs

Abstract

27Werner syndrome (WS) is a prototypic heritable adult human progeroid syndrome in which signs 28 of premature aging are associated with genetic instability and an elevated risk of specific types 29 of cancer. We have quantified mRNA and microRNA (miRNA) expression in WS patient 30 fibroblasts, and in WRN-depleted fibroblasts. Genes down-regulated in WS patient fibroblasts 31 were highly enriched in G-quadruplex (G4) DNA motifs. The strength, location and strand 32 specificity of this association provide strong experimental evidence that G4 motifs or motif-33 dependent G-quadruplexes are bound by WRN in human cells to modulate gene expression. 34The expression of many miRNAs was perturbed by loss of WRN function. WRN depletion 35 altered the expression of >500 miRNAs. miRNAs linked to cell signaling, genome stability 36 assurance and tumorigenesis were among the small number of these miRNAs that were 37 persistently altered in WS patient fibroblasts. An unexpected and highly distinct finding in WS 38 cells was the coordinate over-expression of nearly all cytoplasmic tRNA synthetases and their 39 associated AIMP proteins. Our results provide new insight into WS pathogenesis, and identify 40 therapeutically accessible mechanisms that may drive disease pathogenesis in WS and in the 41 general population. 42 43 Introduction 44 Werner syndrome (WS; OMIM #277700) is an autosomal recessive adult human progeroid 45 syndrome caused by loss of function mutations in the WRN RECQ helicase gene (1) that 46 encodes DNA-dependent ATPase, 3ʹ-to -5ʹ helicase and 3ʹ-to -5ʹ exonuclease activities (2, 3). 47The WS clinical phenotype resembles premature aging: graying and loss of hair, bilateral 48 cataract formation and scleroderma-like skin changes appear in the second decade of life in 49 conjunction with short stature. WS patients are at elevated risk for important, age-associated 50 3 diseases such as atherosclerosis with myocardial infarction and stroke; cancer; osteoporosis; 51 and diabetes mellitus. Of note, there is no elevated risk for Alzheimer disease or other 52 dementias apart from those associated with vascular disease (4). 53Cancer and cardiovascular disease are the leading causes of premature death in WS, most 54 often in the fifth or sixth decades of life (4, 5). The cancer risk in WS patients is limited to a small 55 number of specific neoplasms: acral lentiginous melanoma; meningiomas; soft tissue sarcomas; 56 primary bone tumors, chiefly osteosarcomas; follicular thyroid carcinoma; and likely both 57 leukemia and antecedent myelodysplasia (6). Loss of function mutations in two other members 58 of the five member human RECQ helicase gene family, BLM and RECQL4, respectively cause 59 the cancer predisposition syndromes Bloom syndrome (BS), and Rothmund-Thomson 60 syndrome (RTS) and variants. Both BS and RTS have additional, associated developmental 61 findings (2, 3). 62Biochemical analyses have identified common biochemical substrates for both the WRN and 63 BLM RECQ helicases. These substrates include forked or b...

Stress Marks on the Genome: Use or Lose?

“…Given the demonstrated role of G4 structures in regulation of redox-sensitive gene expression changes [88], factors that modulate the stability of these structures are expected to play significant roles in the process. Interestingly, binding to G4 motifs in target gene promoters and resolution of G4 DNA structures has been suggested as a mechanism of transcriptional regulation by DNA helicases RECQ1 [89,90], XPB, XPD [91], BLM [92], and WRN [93]. However, in vitro biochemical data suggests that the transcriptional regulation by RECQ1 likely does not involve RECQ1 helicase-mediated unwinding of G4 structures [94].…”

G-quadruplexes in Prague: A Bohemian Rhapsody

“…highlighted the role of G-quadruplex helicases, such as XPB [68], BLM [69] and WRN [70] in the up-and down-regulation of quadruplex-containing genes. Treating HT1080 cells for 48 hours with PhenDC caused the dysregulation of 1459 genes by at least two-fold, increasing the transcription of 715 genes and decreasing that of 743 others.…”