ATP-dependent DNA helicase Q4 is an enzyme that in humans is encoded by the RECQL4 gene. [5] [6] [7]
Mutations in RECQL4 are associated with the autosomal recessive disease Rothmund–Thomson syndrome, a disorder that has features of premature aging. [8] [9] In addition to the Rothmund–Thomson syndrome, RECQL4 mutations are also associated with RAPADILINO and Baller–Gerold syndromes. [10] There are two types of Rothmund Thomson syndrome and it is Type 2 that occurs in patients carrying deleterious mutations in both copies of the RECQL4 gene. This condition is associated with a high risk of developing osteosarcoma (malignant tumor of the bone). [11] RECQL4 gets its name from being homologous (sharing sequence) with other members of the RecQ helicase family. Two other genetic diseases are due to mutations in other RECQ helicases. Bloom syndrome is associated with mutations in the BLM gene and Werner syndrome is associated with mutations in the WRN gene. [12]
Double-strand breaks in DNA are potentially lethal to a cell and need to be repaired. Repair of double-strand breaks by homologous recombination (HR) is an important cellular mechanism for avoiding this lethality. RECQL4 has a crucial role in the first step of HR, referred to as end resection. [13] When RECQL4 is deficient, end resection, and thus HR, is reduced. Evidence suggests that other forms of DNA repair including non-homologous end joining, nucleotide excision repair and base excision repair also depend on RECQL4 function. [9] In the Rothmund-Thomson syndrome, the association of deficient RECQL4-mediated DNA repair and premature aging is consistent with the DNA damage theory of aging.
Werner syndrome (WS) or Werner's syndrome, also known as "adult progeria", is a rare, autosomal recessive disorder which is characterized by the appearance of premature aging.
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two hybridized nucleic acid strands, using energy from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases.
RecQ helicase is a family of helicase enzymes initially found in Escherichia coli that has been shown to be important in genome maintenance. They function through catalyzing the reaction ATP + H2O → ADP + P and thus driving the unwinding of paired DNA and translocating in the 3' to 5' direction. These enzymes can also drive the reaction NTP + H2O → NDP + P to drive the unwinding of either DNA or RNA.
Bloom syndrome is a rare autosomal recessive genetic disorder characterized by short stature, predisposition to the development of cancer, and genomic instability. BS is caused by mutations in the BLM gene which is a member of the RecQ DNA helicase family. Mutations in other members of this family, namely WRN and RECQL4, are associated with the clinical entities Werner syndrome and Rothmund–Thomson syndrome, respectively. More broadly, Bloom syndrome is a member of a class of clinical entities that are characterized by chromosomal instability, genomic instability, or both and by cancer predisposition.
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids. It is widely used by cells to accurately repair harmful breaks that occur on both strands of DNA, known as double-strand breaks (DSB), in a process called homologous recombinational repair (HRR). Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt during the course of evolution. Homologous recombination is also used in horizontal gene transfer to exchange genetic material between different strains and species of bacteria and viruses.
Werner syndrome ATP-dependent helicase, also known as DNA helicase, RecQ-like type 3, is an enzyme that in humans is encoded by the WRN gene. WRN is a member of the RecQ Helicase family. Helicase enzymes generally unwind and separate double-stranded DNA. These activities are necessary before DNA can be copied in preparation for cell division. Helicase enzymes are also critical for making a blueprint of a gene for protein production, a process called transcription. Further evidence suggests that Werner protein plays a critical role in repairing DNA. Overall, this protein helps maintain the structure and integrity of a person's DNA.
A DNA repair-deficiency disorder is a medical condition due to reduced functionality of DNA repair.
RAPADILINO syndrome is an autosomal recessive disorder characterized by:
Rothmund–Thomson syndrome (RTS) is a rare autosomal recessive skin condition.
Bloom syndrome protein is a protein that in humans is encoded by the BLM gene and is not expressed in Bloom syndrome.
Three prime repair exonuclease 1 is an enzyme that in humans is encoded by the TREX1 gene.
DNA excision repair protein ERCC-8 is a protein that in humans is encoded by the ERCC8 gene.
The human gene UBR1 encodes the enzyme ubiquitin-protein ligase E3 component n-recognin 1.
ATP-dependent DNA helicase Q5 is an enzyme that in humans is encoded by the RECQL5 gene.
The DNA damage theory of aging proposes that aging is a consequence of unrepaired accumulation of naturally occurring DNA damage. Damage in this context is a DNA alteration that has an abnormal structure. Although both mitochondrial and nuclear DNA damage can contribute to aging, nuclear DNA is the main subject of this analysis. Nuclear DNA damage can contribute to aging either indirectly or directly.
Synthetic lethality is defined as a type of genetic interaction where the combination of two genetic events results in cell death or death of an organism. Although the foregoing explanation is wider than this, it is common when referring to synthetic lethality to mean the situation arising by virtue of a combination of deficiencies of two or more genes leading to cell death, whereas a deficiency of only one of these genes does not. In a synthetic lethal genetic screen, it is necessary to begin with a mutation that does not result in cell death, although the effect of that mutation could result in a differing phenotype, and then systematically test other mutations at additional loci to determine which, in combination with the first mutation, causes cell death arising by way of deficiency or abolition of expression.
Fanconi anemia, complementation group M, also known as FANCM is a human gene. It is an emerging target in cancer therapy, in particular cancers with specific genetic deficiencies.
Progeroid syndromes (PS) are a group of rare genetic disorders that mimic physiological aging, making affected individuals appear to be older than they are. The term progeroid syndrome does not necessarily imply progeria, which is a specific type of progeroid syndrome.
Baller–Gerold syndrome (BGS) is a rare genetic syndrome that involves premature fusion of the skull bones and malformations of facial, forearm and hand bones. The symptoms of Baller–Gerold syndrome overlap with features of a few other genetics disorders: Rothmund–Thomson syndrome and RAPADILINO syndrome. The prevalence of BGS is unknown, as there have only been a few reported cases, but it is estimated to be less than 1 in a million. The name of the syndrome comes from the researchers Baller and Gerold who discovered the first three cases.
A cancer syndrome, or family cancer syndrome, is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Cancer syndromes often show not only a high lifetime risk of developing cancer, but also the development of multiple independent primary tumors.