1.5 DNA repair mechanism
DNA double strand breaks (DBSs) and single-strand breaks (SSBs) occur every day in cells and they are mostly caused by ionizing radiation, ultraviolet light, reactive oxygen species, errors during DNA replication, enzymes during meiosis. The repair of these DSBs and SSBs is essential to maintain genomic fidelity and stability. In order to combat DBSs and SSBs, cells have developed multiple distinct DNA repair mechanisms which detect damaged DNA, signal its presence and promote the repair of the damage (Jackson and Bartek, 2009). One of these mechanisms is base excision repair (BER). BER is a multi-step process that corrects non-bulky damage to bases resulting from oxidation, methylation, deamination, or spontaneous loss of the DNA base itself. In BER, DNA glycosylase recognises the damaged base and mediates base removal before proliferating cell nuclear antigen (PCNA), polymerase β and DNA ligase I or DNA Ligase III complete the repair process (Jackson and Bartek, 2009, David et al., 2007). Nucleotide excision repair (NER) is perhaps the most flexible of the DNA repair pathways. NER recognises and repairs lesions which are caused by helical distortion of the DNA duplex and pyrimidine dimers (cyclobutane pyrimidine dimers and 6-4 photoproducts) which are caused by the UV component of sunlight. Other NER substrates include bulky chemical adducts, DNA intrastrand crosslinks, and some forms of oxidative damage. Two distinct NER pathways exist: transcription-coupled NER which focuses on lesion blocking transcriptions and global genome NER which surveys the entire genome for distorting damage (Jackson and Bartek, 2009, David et al., 2007 ). DNA mismatch repair (MMR) pathway plays an essential role in the correc...
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...ing proteins. The large protein kinase, consisting of 4128 amino acids (aa), has a molecular weight of 469 kDA (33, 85-87). DNA-PKcs associates with the Ku70/80 heterodimer and forms a catalytic active DNA-PK holoenzyme (Falck et al., 2005). The kinase activity of DNA-PKcs is activated upon interaction with a free DNA. The protein can bind to DNA fragments in absence of the Ku complex. However its kinase activity appears to be much lower (Hammarsten and Chu, 1998). DNA-PKcs mediates the synapsis and ligation of the two DNA fragments (Block et al., 2004; Kysela et al., 2005). The auto-phosphorylation of DNA-PKcs results in the remodelling of DNA-Pk (Block et al., 2004). Moreover, DNA-PK phosphorylates the histons H2AX and H1.This might indicate that DNA-PK modifies chromatin structure to facilitate the access of other DNA repair complexes to DSBs (Kysela et al., 2005
The IC50 values of LJI308 against RSK1, 2, and 3 were about0.004 - 0.013 mmol/L. 10 μMLJI308 could bind to nearly 100% of theRSK2. LJI308 boundtheN-terminiofRSK1, RSK3, and RSK4 to a similar extent. LJI308 inhibited S6K1 with an IC50 of 0.8 mM. In both MDA-MB-231 and H358 cell lines, 1 μM and 10 μM LJI308 exihibited an inhibitory effect on colony formation and cell growthwith a different sensitivity[1]. In HTRY-LT cell lines,treating withLJI308 (1-10 µM) after4 or 8 days decreased the cellviability by up to 90%; while little to no effect wasobserved in the non-tumorigenic HTRZ cells [2].
... Thus, the loss of BRCA1 can result in defective DNA damage repair, abnormal centrosome duplication, cell-cycle arrest, growth retardation, increased apoptosis, genetic instability and tumorigenesis2. The study of BRCA1 mutation in mice may be used for new therapeutic approaches, although the cause of the mutation in BRCA gene is unclear.
Tomida J, Itaya A, Shigechi T, Unno J, Uchida E, Ikura M, Masuda Y, Matsuda S, Adachi J, Kobayashi M, Meetei AR, Maehara Y, Yamamoto K, Kamiya K, Matsuura A, Matsuda T, Ikura T, Ishiai M and Takata M. 2013. A novel interplay between the Fanconi anemia core complex and ATR-ATRIP kinase during DNA cross-link repair. Nucleic Acids Res. 41: 6930-6941.
A permanent change in the DNA sequence which makes up a gene is what is referred to as gene mutation (Mahoney & Springer 2009). It is believed that gene mutation occurs in two ways: that is, it can be acquired in personal lifetime or inherited from a parent. Those that are passed from parents to the child are referred to as hereditary mutation. They acquire the name since they are present in the eggs and sperms or the germ cell. In this case, such kind of mutation is present all through one’s life in almost every cell in the body. A similarity in mutation and gene diversity is the change in the DNA sequence which makes both mutation and genetic diversity have related issues.
DNA methylation primarily occurs within sites in the DNA sequence known as CpG dinucleotides, which is a 2 base pair sequence involving a Cytosine bonded to a Guanine by a phosphodiester bond.
If DNA has been impacted by these free radical lesion, it most likely loses its ability to repair itself. In this case, it will require certain proteins to single out these damaged areas in order for the cell to restore itself to proper conditions. Smaller lesions can be reversed chemically, but the only thing that can be done for larger ones is to be completely removed. If this happens, the cell will require the help of repair enzymes that step in to replicate and restore the empty area.
In some organism PDK 2 activates AKT by phosphorylating it at S473 sequence in regulatory domain. Activated ATK further regulates many cellular downstream processes (Fig 2).
Yang, Q. (2009). Cellular senescence, telomere recombination and maintenance. Cytogenetic and Genome Research, 122(3-4), 211-8. Retrieved from http://search.proquest.com/docview/224206989?accountid=28496
Precise chromosomal DNA replication during S phase of the cell cycle is a crucial factor in the proper maintenance of the genome from generation to generation. The current “once-per-cell-cycle” model of eukaryotic chromosome duplication describes a highly coordinated process by which temporally regulated replicon clusters are sequentially activated and subsequently united to form two semi-conserved copies of the genome. Replicon clusters, or replication domains, are comprised of individual replication units that are synchronously activated at predetermined points during S phase. Bi-directional replication within each replicon is initiated at periodic AT-rich origins along each chromosome. Origins are not characterized by any specific nucleotide sequence, but rather the spatial arrangement of origin replication complexes (ORCs). Given the duration of the S phase and replication fork rate, adjacent origins must be appropriately spaced to ensure the complete replication of each replicon. Chromatin arrangement by the nuclear matrix may be the underpinning factor responsible for ORC positioning. The six subunit ORC binds to origins of replication in an ATP-dependent manner during late telophase and early G1. In yeast, each replication domain simply contains a single ORC binding site. However, more complex origins are characterized by an initiation zone where DNA synthesis may begin at numerous locations. A single round of DNA synthesis at each activated origin is achieved by “lic...
The patients in the Chen, et al., 2003 study suffered from damaged colonic epithelium because of “elevated levels of reactive oxygen species (ROS) and reduced oxidative defenses” (Chen et al., 2003). ROS are chemical species containing oxygen. This is another cause of genomic instability, in turn, this will lead to tumor formation and progression. Not only did the reactive oxygen species cause damage to the colonic epithelium but it also induces genetic damage to the DNA. The DNA received acute damage from base alterations, abasic sites, and strand breaks.
The use of Proteinase K and Homogenization Buffer (HB) is used to cause the cell to lyse, breaking down the lipid cell membrane, digesting unwanted proteins and removing contamination that might otherwise degrade the DNA. This allows for the DNA to become free floating.
Discoveries in DNA, cell biology, evolution, and biotechnology have been among the major achievements in biology over the past 200 years with accelerated discoveries and insight’s over the last 50 years. Consider the progress we have made in these areas of human knowledge. Present at least three of the discoveries you find to be the most important and describe their significance to society, heath, and the culture of modern life.
Free radicals are highly reactive atoms or polyatomic ions that have unpaired valence electrons. These unpaired electrons can bind to organic compounds, changing the structure of the substance (Halliwell, B.). In most cases, oxygen-free radicals (OFRs) and reactive oxygen species (ROSs) are byproducts of metabolism. OFRs originate from the metabolic process in mitochondria when oxygen molecules accept an extra electron (Raha, S. et al). While oxygen is necessary for respiration, OFRs can bind to cellular components like DNA bases or the deoxyribose backbone of DNA, which plays a key-role in the aging process and is also linked to the development of certain cancers (Valko, M. et al). The ability of OFRs and ROSs to bind to DNA causes breaks in the structure of DNA and is the reason why these
And this property of Endo V allows other proteins to complete the downstream repair process. So this study signifies that acts as a strong DNA repair protein. Also the activity of EndoV is not complete without a metal factor of Mg2+ that is responsible for the catalysis of this enzyme. Also the metal factor upon binding with DNA it actually shows 3’ and 5’ non-specific exonuclease activity. This was demonstrated using a 5’ and 3’ labeled inosine containing DNA and H2124D mutant, where the actual 3’ exonuclease activity was
DNA manipulation is one of the sensational topic that exist in our contemporary society. Manipulating DNA basically means changing the forms or the structure DNA of certain thing to change the traits genetically. Some people believe that manipulating DNA have multiple risks. However, I firmly believe that there are relatively more benefits than dangers, and I am going to inform about those benefits. First, changing DNA could stop the problem of famine.