Quia - DNA, RNA, replication, protein synthesis, quiz
DNA, RNA and Protein Synthesis
DNA, RNA, replication, protein synthesis, quiz
The nucleoside analogue 5-FU is converted to severalactive metabolites, including fluorouridine triphosphate (FUTP),fluorodeoxyuridine triphosphate (FdUTP) and fluorodeoxyuridinemonophosphate (FdUMP), to exert its cytotoxic activity (). FUTP is largely incorporated intothe RNA strand, preventing the processing and function of varioustypes of RNA including mRNA, rRNA, tRNA and snRNA to exertanticancer effect of 5-FU ().Recently, several lines of evidence suggest that these metabolitesof 5-FU also interrupt DNA metabolism by misincorporation or enzymeinhibition (). For example, FdUMPdisturbs DNA replication by inhibiting the activity of thymidylatesynthetase (TS), through the depletion of dTMP. 5-FU may alsogenerate DNA damage, such as DNA single-strand breaks and/or DNAdouble strand breaks (DSBs) via the collapse of stalled replicationforks. Although the induction of DNA damage has been shown to playa role in the anticancer effect of 5-FU (–), themeans by which the metabolites of 5-FU exert their anticancereffects through the disturbance of DNA or RNA metabolism remainobscure ().
We next examined if RRM-1 is involved in thesynergic effect of the combinational treatment, since RRM-1 plays arole in the 5-FU-induced DNA damage in TE11 cells (). We performed a clonogenic assayof RRM-1-depleted cells after the 5-FU/CDDP treatment. As expected,the depletion of RRM-1 with siRNA significantly increased thesurvival of TE11 cells after the combinational treatment(p). Since RRM-1depletion did not affect the 5-FU or CDDP sensitivity of TE11( and , p=0.90), this finding suggests theinvolvement of RRM-1 in the synergic effect of the combinationregimen with 5-FU and CDDP in TE11 cells.
DNA / RNA Protein Synthesis Online Quiz - zeroBio
Next we investigated the survival of these cellsafter 5-FU treatment by a clonogenic assay, to determine whetherRRM-1 depletion is involved in 5-FU sensitivity. Representativedose-survival responses of 5-FU are depicted in . The Dm values for 5-FU wereestimated as 3.34 M in RRM-1 siRNA treated cells and 3.44M in control cells. Therefore, a significant change in 5-FUsensitivity by the depletion of RRM-1 was not observed. The reducedanticancer activity of 5-FU, through the lower induction of DNAdamage, might be compensated by the increased disturbance of RNAmetabolism by the depletion of RRM-1.
In spite of the requirement of RRM-1 for theinduction of DNA damage, the expression levels of RRM-1 did notaffect the survival of TE11 cells after 5-FU alone treatment(). Metabolites of 5-FU candisturb either DNA or RNA metabolisms (). RRM-1 depletion could lead toincreased conversion of 5-FU into 5-FUTP which contributes to theanticancer effect of 5-FU at several levels in RNA metabolism(). The misincorporation ofFUTP into RNA may inhibit the processing of pre-rRNA into maturerRNA (,). In addition, it may disrupt thepost-transcriptional modifications of tRNAs (,)and the assembly and activity of snRNA/protein complexes, thusinhibiting the splicing of pre-mRNAs (,).Therefore, the decreased induction of DNA damage by the depletionof RRM-1 after 5-FU treatment could be compensated by the increaseddisturbance of RNA metabolism, through the increased level of5-FUTP in TE11 cells. Still further investigation to clarify thedisturbance of RNA metabolism by the RRM-1 depletion is required,RRM-1 may play a key role in the regulation of the anticancereffect of 5-FU alone by disturbing either DNA or RNAmetabolism.
whereas DNA and RNA are composed of ___ different nucleotides ..
Forkhead box M1 (FOXM1), previously named HNF-3, HFH-11 or Trident, is a transcription factor of the Forkhead box (Fox) protein superfamily which is defined by a conserved winged helix DNA-binding domain. FOXM1 is a key regulator of both G1/S and G2/M phases of the cell cycle and mitotic spindle integrity. Besides its involvement in cell cycle transitions, it also plays an important role in angiogenesis, metastasis, apoptosis, DNA damage repair and tissue regeneration. The human FOXM1 gene consists of 10 exons of which two are alternatively spliced. These splice events give rise to three different splice variants named FOXM1a, -b and -c. FOXM1b and FOXM1c act as transactivators and can activate their target genes by two different mechanisms. They both activate through binding to conventional FOXM1 binding sites 5’-A(C/T)AAA(C/T)AA-3’ while FOXM1c can additionally activate genes by binding to the TATA-boxes. The splice variant FOXM1a is transcriptionally inactive due to disruption of the transactivation domain and might also cause dominant-negative effects as it has retained a functional DNA binding domain. FOXM1 is ubiquitously expressed in proliferating cells and has a positive effect on cell growth by promoting G1/S as well as G2/M-transition during the cell cycle. Its expression levels are shown to correlate with the proliferative state of a cell and are antagonistically regulated by proliferation and anti-proliferation signals. In quiescent or terminally differentiated cells FOXM1 levels are barely detectable. FOXM1 deficient cells show polyploidy, aneuploidy, defects in cytokinesis, chromosome missegregation as well as an increase in the number of DNA breaks. These findings suggest an important role of FOXM1 in the maintenance of genome stability and DNA damage repair. Additionally, cells exposed to DNA damaging radiation show an increase in FOXM1 protein levels indicating its involvement in DNA repair processes. Post-translational modifications play an important role in the regulation of FOXM1. The phosphorylation condition of FOXM1 determines its cellular localisation and activation state. Phosphorylation by Raf-MEK-ERK causes FOXM1 to translocate from the cytoplasm into the nucleus during late S-phase after which further phosphorylation steps take place. Hyperphosphorylation during G2-M phase correlates with increased transcriptional activity of FOXM1 which suggests phosphorylation as an important regulation step in the activation of the protein. Conserved putative phosphorylation sites indicate the involvement of various Cyclin-Cdk complexes as well as the mitogen-activated protein kinase (MAPK) cascade. Furthermore, phosphorylation by checkpoint kinase 2 in response to DNA damage was shown to increase FOXM1 stability and its transcriptional activity. The important roles of FOXM1 during cell cycle progression and DNA damage repair have given this transcription factor a crucial role within the development and progression of many cancers, including colorectal , lung , prostate , liver and breast cancer . A microarray study also shows that FOXM1 expression is elevated in carcinomas of the prostate, lung, ovary, colon, pancreas, stomach, bladder, liver, kidney and breast . In most human tumours FOXM1 levels are significantly higher while the expression level increases with tumour grade and is inversely correlated with patient survival.
For years, the exact means by which the DNA coded for structures, chemicals and other behaviors in living things was a mystery. Scientists now know which mRNA codons match each amino acid. This means that if you know the sequence of DNA or mRNA, you can figure out the sequence of amino acids that make a protein.
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DNA, RNA, Protein Synthesis Worksheet / Study Guide
This is a five page worksheet on DNA, RNA, and protein synthesis
Arnaudeau C, Lundin C and Helleday T: DNAdouble-strand breaks associated with replication forks arepredominantly repaired by homologous recombination involving anexchange mechanism in mammalian cells. J Mol Biol. 307:1235–1245.2001. :
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