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Stem Cells (Dayton, Ohio) Sep 2020Telomeres are composed of repetitive DNA sequences that are replenished by the enzyme telomerase to maintain the self-renewal capacity of stem cells. The RNA component... (Review)
Review
Telomeres are composed of repetitive DNA sequences that are replenished by the enzyme telomerase to maintain the self-renewal capacity of stem cells. The RNA component of human telomerase (TERC) is the essential template for repeat addition by the telomerase reverse transcriptase (TERT), and also serves as a scaffold for several factors comprising the telomerase ribonucleoprotein (RNP). Unique features of TERC regulation and function have been informed not only through biochemical studies but also through human genetics. Disease-causing mutations impact TERC biogenesis at several levels including RNA transcription, post-transcriptional processing, folding, RNP assembly, and trafficking. Defects in TERC reduce telomerase activity and impair telomere maintenance, thereby causing a spectrum of degenerative diseases called telomere biology disorders (TBDs). Deciphering mechanisms of TERC dysregulation have led to a broader understanding of noncoding RNA biology, and more recently points to new therapeutic strategies for TBDs. In this review, we summarize over two decades of work revealing mechanisms of human telomerase RNA biogenesis, and how its disruption causes human diseases.
PubMed: 32875693
DOI: 10.1002/stem.3270 -
G3 (Bethesda, Md.) Nov 2023Aging is the consequence of intra- and extracellular events that promote cellular senescence. Dyskeratosis congenita (DC) is an example of a premature aging disorder...
Aging is the consequence of intra- and extracellular events that promote cellular senescence. Dyskeratosis congenita (DC) is an example of a premature aging disorder caused by underlying telomere/telomerase-related mutations. Cells from these patients offer an opportunity to study telomere-related aging and senescence. Our previous work has found that telomere shortening stimulates DNA damage responses (DDRs) and increases reactive oxygen species (ROS), thereby promoting entry into senescence. This work also found that telomere elongation via TERT expression, the catalytic component of the telomere-elongating enzyme telomerase, or p53 shRNA could decrease ROS by disrupting this telomere-DDR-ROS pathway. To further characterize this pathway, we performed a CRISPR/Cas9 knockout screen to identify genes that extend life span in DC cells. Of the cellular clones isolated due to increased life span, 34% had a guide RNA (gRNA) targeting CEBPB, while gRNAs targeting WSB1, MED28, and p73 were observed multiple times. CEBPB is a transcription factor associated with activation of proinflammatory response genes suggesting that inflammation may be present in DC cells. The inflammatory response was investigated using RNA sequencing to compare DC and control cells. Expression of inflammatory genes was found to be significantly elevated (P < 0.0001) in addition to a key subset of these inflammation-related genes [IL1B, IL6, IL8, IL12A, CXCL1 (GROa), CXCL2 (GROb), and CXCL5]. which are regulated by CEBPB. Exogenous TERT expression led to downregulation of RNA/protein CEBPB expression and the inflammatory response genes suggesting a telomere length-dependent mechanism to regulate CEBPB. Furthermore, unlike exogenous TERT and p53 shRNA, CEBPB shRNA did not significantly decrease ROS suggesting that CEBPB's contribution in DC cells' senescence is ROS independent. Our findings demonstrate a key role for CEBPB in engaging senescence by mobilizing an inflammatory response within DC cells.
Topics: Humans; Reactive Oxygen Species; Dyskeratosis Congenita; Telomerase; Tumor Suppressor Protein p53; Mutation; Telomere; RNA, Small Interfering; Fibroblasts; Inflammation; Mediator Complex; CCAAT-Enhancer-Binding Protein-beta
PubMed: 37717172
DOI: 10.1093/g3journal/jkad207 -
The Journal of Biological Chemistry Sep 2023The levels of non-coding RNAs (ncRNAs) are regulated by transcription, RNA processing, and RNA degradation pathways. One mechanism for the degradation of ncRNAs involves... (Review)
Review
The levels of non-coding RNAs (ncRNAs) are regulated by transcription, RNA processing, and RNA degradation pathways. One mechanism for the degradation of ncRNAs involves the addition of oligo(A) tails by non-canonical poly(A) polymerases, which then recruit processive sequence-independent 3' to 5' exonucleases for RNA degradation. This pathway of decay is also regulated by three 3' to 5' exoribonucleases, USB1, PARN, and TOE1, which remove oligo(A) tails and thereby can protect ncRNAs from decay in a manner analogous to the deubiquitination of proteins. Loss-of-function mutations in these genes lead to premature degradation of some ncRNAs and lead to specific human diseases such as Poikiloderma with Neutropenia (PN) for USB1, Dyskeratosis Congenita (DC) for PARN and Pontocerebellar Hypoplasia type 7 (PCH7) for TOE1. Herein, we review the biochemical properties of USB1, PARN, and TOE1, how they modulate ncRNA levels, and their roles in human diseases.
Topics: Humans; Dyskeratosis Congenita; Exoribonucleases; Neutropenia; RNA Stability; RNA, Untranslated; Loss of Function Mutation
PubMed: 37544646
DOI: 10.1016/j.jbc.2023.105139 -
The Annals of Otology, Rhinology, and... Sep 2022Dyskeratosis congenita (DC) is a progressive congenital disorder that predisposes patients to squamous cell cancers (SCC) of the head and neck. We report a case of a...
OBJECTIVES
Dyskeratosis congenita (DC) is a progressive congenital disorder that predisposes patients to squamous cell cancers (SCC) of the head and neck. We report a case of a patient who underwent primary osteocutaneous free flap for mandibular SCC followed by additional treatments for positive margins and discuss a systematic review on therapeutic management for this patient population.
METHODS
Case report of a 39-year-old male with DC who underwent resection and reconstruction with a fibular free flap for mandible SCC, followed by revision surgery and adjuvant radiotherapy for positive margins. A systematic review was completed afterward with the following terms: "dyskeratosis congenita" AND "oral cancer" OR "head and neck" OR "otolaryngology" on Medline and Web of Science for articles between 1980 and 2021. In total, 12 articles were included that reported on DC and SCC in the head and neck.
RESULTS
Of the case reports that were included in this review, half the patients had recurrence within 1 year of primary treatments. Only 2 patients did not require revision surgery, adjuvant, or salvage therapy. Half of patients that received radiation therapy had severe side effects.
CONCLUSIONS
This is the largest review of DC and SCC in the head and neck. Based off our case report and review, these patients have aggressive disease that often requires multi-modality treatment. Consideration should be taken in regards to reports of side effects with radiation therapy.
Topics: Adult; Carcinoma, Squamous Cell; Epithelial Cells; Free Tissue Flaps; Head and Neck Neoplasms; Humans; Male; Plastic Surgery Procedures
PubMed: 34651516
DOI: 10.1177/00034894211047470 -
Frontiers in Oncology 2023Dyskeratosis congenita (DKC), also known as Zinsser-Cole-Engman syndrome, is a telomeropathy typically presenting as a triad of leukoplakia, nail dystrophy, and...
Dyskeratosis congenita (DKC), also known as Zinsser-Cole-Engman syndrome, is a telomeropathy typically presenting as a triad of leukoplakia, nail dystrophy, and reticular hyperpigmentation. Reported genetic mutations linked to DKC include , , , , , , , , and . Homozygous, compound heterozygous, and heterozygous mutations in (, regulator of telomere elongation helicase 1) gene on chromosome 20q13 are known to cause autosomal dominant as well as recessive DKC. Pathogenic variants of gene in patients include c.2288G>T (p. Gly763Val), c.3791G>A (p. Arg1264His), and p. Arg981Trp. We report a novel homozygous variant of , transcript ID: ENST00000360203.11, exon 24, c.2060C>T (p.Ala687Val), in a patient of DKC presenting with leukoplakia, dystrophic nails, reticulate pigmentation, and positive family history of a similar phenotype. The novel variant, reported as a variant of uncertain significance, may therefore be considered diagnostic for DKC in a Pakistani population.
PubMed: 36937416
DOI: 10.3389/fonc.2023.1098876 -
ELife May 2022Dyskeratosis congenita (DC) is a rare genetic disorder characterized by deficiencies in telomere maintenance leading to very short telomeres and the premature onset of...
Dyskeratosis congenita (DC) is a rare genetic disorder characterized by deficiencies in telomere maintenance leading to very short telomeres and the premature onset of certain age-related diseases, including pulmonary fibrosis (PF). PF is thought to derive from epithelial failure, particularly that of type II alveolar epithelial (AT2) cells, which are highly dependent on Wnt signaling during development and adult regeneration. We use human induced pluripotent stem cell-derived AT2 (iAT2) cells to model how short telomeres affect AT2 cells. Cultured DC mutant iAT2 cells accumulate shortened, uncapped telomeres and manifest defects in the growth of alveolospheres, hallmarks of senescence, and apparent defects in Wnt signaling. The GSK3 inhibitor, CHIR99021, which mimics the output of canonical Wnt signaling, enhances telomerase activity and rescues the defects. These findings support further investigation of Wnt agonists as potential therapies for DC-related pathologies.
Topics: Alveolar Epithelial Cells; Dyskeratosis Congenita; Glycogen Synthase Kinase 3; Humans; Induced Pluripotent Stem Cells; Mutation; Telomerase; Telomere
PubMed: 35559731
DOI: 10.7554/eLife.64430 -
BMC Bioinformatics Apr 2021Harmonin Homogy Domains (HHD) are recently identified orphan domains of about 70 residues folded in a compact five alpha-helix bundle that proved to be versatile in...
BACKGROUND
Harmonin Homogy Domains (HHD) are recently identified orphan domains of about 70 residues folded in a compact five alpha-helix bundle that proved to be versatile in terms of function, allowing for direct binding to a partner as well as regulating the affinity and specificity of adjacent domains for their own targets. Adding their small size and rather simple fold, HHDs appear as convenient modules to regulate protein-protein interactions in various biological contexts. Surprisingly, only nine HHDs have been detected in six proteins, mainly expressed in sensory neurons.
RESULTS
Here, we built a profile Hidden Markov Model to screen the entire UniProtKB for new HHD-containing proteins. Every hit was manually annotated, using a clustering approach, confirming that only a few proteins contain HHDs. We report the phylogenetic coverage of each protein and build a phylogenetic tree to trace the evolution of HHDs. We suggest that a HHD ancestor is shared with Paired Amphipathic Helices (PAH) domains, a four-helix bundle partially sharing fold and functional properties. We characterized amino-acid sequences of the various HHDs using pairwise BLASTP scoring coupled with community clustering and manually assessed sequence features among each individual family. These sequence features were analyzed using reported structures as well as homology models to highlight structural motifs underlying HHDs fold. We show that functional divergence is carried out by subtle differences in sequences that automatized approaches failed to detect.
CONCLUSIONS
We provide the first HHD databases, including sequences and conservation, phylogenic trees and a list of HHD variants found in the auditory system, which are available for the community. This case study highlights surprising phylogenetic properties found in orphan domains and will assist further studies of HHDs. We unveil the implication of HHDs in their various binding interfaces using conservation across families and a new protein-protein surface predictor. Finally, we discussed the functional consequences of three identified pathogenic HHD variants involved in Hoyeraal-Hreidarsson syndrome and of three newly reported pathogenic variants identified in patients suffering from Usher Syndrome.
Topics: Amino Acid Sequence; Dyskeratosis Congenita; Fetal Growth Retardation; Humans; Membrane Proteins; Phylogeny
PubMed: 33853521
DOI: 10.1186/s12859-021-04116-5 -
Lipoprotein particle alterations due to androgen therapy in individuals with dyskeratosis congenita.EBioMedicine Jan 2022Dyskeratosis congenita (DC) is a telomere biology disorder associated with high rates of bone marrow failure (BMF) and other medical complications. Oral androgens are...
BACKGROUND
Dyskeratosis congenita (DC) is a telomere biology disorder associated with high rates of bone marrow failure (BMF) and other medical complications. Oral androgens are successfully used to treat BMF in DC but often have significant side effects, including elevation of serum lipids. This study sought to determine the extent to which oral androgen therapy altered lipid and lipoprotein levels.
METHODS
Nuclear magnetic resonance (NMR) was used to evaluate serum lipid profiles, and lipoprotein particle number and size in nine androgen-treated individuals with DC, 45 untreated individuals with DC, 72 unaffected relatives of DC patients, and 19 untreated individuals with a different inherited BMF syndrome, Fanconi anaemia (FA).
FINDINGS
Androgen-treated individuals with DC had significantly decreased serum HDL cholesterol, HDL particle number and HDL particle size (p < 0·001, p < 0·001 and p < 0·001, respectively); significantly increased serum LDL cholesterol and LDL particle number (p < 0·001, p < 0·001, respectively), decreased apoA-I and increased apoB (p < 0⋅001, p < 0⋅05 respectively) when compared with untreated individuals with DC. There were no significant lipid profile differences between untreated DC and untreated FA participants; or between untreated DC participants and their unaffected relatives. Branched chain amino acids and lipoprotein insulin resistance were not significantly different with androgen treatment. GlycA, an inflammatory acute phase reactant, was significantly increased with androgen treatment (p < 0⋅001).
INTERPRETATION
Androgen treatment in DC creates an atherogenic lipoprotein profile, raising concern for the potential of elevated cardiovascular disease risk. Clinical guidelines for individuals on androgens for DC-related BMF should include cardiovascular disease monitoring. These findings could be relevant in individuals treated with androgen for other indications.
FUNDING
Intramural research programs of the Division of Cancer Epidemiology and Genetics of the National Cancer Institute and National Heart, Lung, and Blood Institute.
Topics: Androgens; Apolipoproteins B; Dyskeratosis Congenita; Humans; Lipoproteins; Telomere
PubMed: 34929494
DOI: 10.1016/j.ebiom.2021.103760 -
Cancer Reports (Hoboken, N.J.) Jan 2023With the progression of next-generation sequencing technologies, researchers have identified numerous variants of the regulator of telomere elongation helicase 1 (RTEL1)... (Review)
Review
BACKGROUND
With the progression of next-generation sequencing technologies, researchers have identified numerous variants of the regulator of telomere elongation helicase 1 (RTEL1) gene that are associated with a broad spectrum of phenotypic manifestations, including malignancies. At the molecular level, RTEL1 is involved in the regulation of the repair, replication, and transcription of deoxyribonucleic acid (DNA) and the maintenance of telomere length. RTEL1 can act both as a promotor and inhibitor of tumorigenesis. Here, we review the potential mechanisms implicated in the malignant transformation of tissues under conditions of RTEL1 deficiency or its aberrant overexpression.
RECENT FINDINGS
A major hemostatic challenge during RTEL1 dysfunction could arise from its unbalanced activity for unwinding guanine-rich quadruplex DNA (G4-DNA) structures. In contrast, RTEL1 deficiency leads to alterations in telomeric and genome-wide DNA maintenance mechanisms, ribonucleoprotein metabolism, and the creation of an inflammatory and immune-deficient microenvironment, all promoting malignancy. Additionally, we hypothesize that functionally similar molecules could act to compensate for the deteriorated functions of RTEL1, thereby facilitating the survival of malignant cells. On the contrary, RTEL1 over-expression was directed toward G4-unwinding, by promoting replication fork progression and maintaining intact telomeres, may facilitate malignant transformation and proliferation of various pre-malignant cellular compartments.
CONCLUSIONS
Therefore, restoring the equilibrium of RTEL1 functions could serve as a therapeutic approach for preventing and treating malignancies.
Topics: Humans; DNA; Neoplasms; Telomere; Tumor Microenvironment; DNA Helicases
PubMed: 36253342
DOI: 10.1002/cnr2.1735 -
Leukemia Jun 2024Recent advances in in-depth data-independent acquisition proteomic analysis have enabled comprehensive quantitative analysis of >10,000 proteins. Herein, an integrated...
Recent advances in in-depth data-independent acquisition proteomic analysis have enabled comprehensive quantitative analysis of >10,000 proteins. Herein, an integrated proteogenomic analysis for inherited bone marrow failure syndrome (IBMFS) was performed to reveal their biological features and to develop a proteomic-based diagnostic assay in the discovery cohort; dyskeratosis congenita (n = 12), Fanconi anemia (n = 11), Diamond-Blackfan anemia (DBA, n = 9), Shwachman-Diamond syndrome (SDS, n = 6), ADH5/ALDH2 deficiency (n = 4), and other IBMFS (n = 18). Unsupervised proteomic clustering identified eight independent clusters (C1-C8), with the ribosomal pathway specifically downregulated in C1 and C2, enriched for DBA and SDS, respectively. Six patients with SDS had significantly decreased SBDS protein expression, with two of these not diagnosed by DNA sequencing alone. Four patients with ADH5/ALDH2 deficiency showed significantly reduced ADH5 protein expression. To perform a large-scale rapid IBMFS screening, targeted proteomic analysis was performed on 417 samples from patients with IBMFS-related hematological disorders (n = 390) and healthy controls (n = 27). SBDS and ADH5 protein expressions were significantly reduced in SDS and ADH5/ALDH2 deficiency, respectively. The clinical application of this first integrated proteogenomic analysis would be useful for the diagnosis and screening of IBMFS, where appropriate clinical screening tests are lacking.
Topics: Humans; Bone Marrow Failure Disorders; Proteogenomics; Male; Female; Bone Marrow Diseases; Child; Adult; Adolescent; Child, Preschool; Anemia, Diamond-Blackfan; Young Adult; Fanconi Anemia; Proteomics; Infant; Shwachman-Diamond Syndrome; Dyskeratosis Congenita
PubMed: 38740980
DOI: 10.1038/s41375-024-02263-1