Transcription process

The purpose of this eornpuLer project is Lo examine several polynuclear aromatic hydrocarbons and to relate their electron density patterns to their carcinogenic activity. If nucleophilic binding to DN.A is a significant step in blocking the normal transcription process of DN.A, electron density in the hydrocarbon should be positively correlated to its carcinogenic potency. To begin with, we shall rely on clinical evidence that benzene, naphthalene, and phenanthrene... 

Goldman, D. S., Kiessling, A. A., and Cooper, G. M. (1988). Post-transcriptional processing suggests that c-mos functions as a maternal message in mouse eggs. Oncogene 3 159-162. 

S.-i. Kawano, S.-i. Tamaru, N. Fujita, and S. Shinkai, Sol-gel polycondensation of tetraethyl orthosilicate (TEOS) in sugar-based porphyrin organogels Inorganic conversion of a sugar-directed porphyrinic fiber library through sol-gel transcription processes, Chem. Eur. J., 10 (2004) 343-351. 

One way to control how much of something a cell uses or makes is to control the levels of the enzymes that are required to metabolize it (Fig. 5-7). Whether or not transcription happens is controlled by the binding of specific proteins to the DNA. When they bind to DNA, these proteins can either help or hinder the transcription process. Positive and negative refer only to the effect a protein has when it binds to the DNA. A positive effect is when the protein binds to the DNA and turns on the transcription of the gene. A negative effect is when the binding of the protein to the DNA turns off transcription. 

Current hypotheses indicate that B-cell transcriptional processes are disrupted, which prevent expression of B-cell surface markers and production of immunoglobulin messenger RNA. Alterations in the normal apoptotic pathways favor cell survival and proliferation. 

Figure 4.27 The post-transcriptional processing of yeast tRNATyr. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)...

Transcription Factors Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process. [NIH]... 

Heterogeneous nuclear RNA (huRNA or pre-mRNA), which is found only in the nucleus of eukaryotic cells. It represents precursors of mRNA, formed during its post-transcriptional processing. 

These three compounds exert many similar effects in nucleotide metabolism of chicks and rats [167]. They cause an increase of the liver RNA content and of the nucleotide content of the acid-soluble fraction in chicks [168], as well as an increase in rate of turnover of these polynucleotide structures [169,170]. Further experiments in chicks indicate that orotic acid, vitamin B12 and methionine exert a certain action on the activity of liver deoxyribonuclease, but have no effect on ribonuclease. Their effect is believed to be on the biosynthetic process rather than on catabolism [171]. Both orotic acid and vitamin Bu increase the levels of dihydrofolate reductase (EC 1.5.1.4), formyltetrahydrofolate synthetase and serine hydroxymethyl transferase in the chicken liver when added in diet. It is believed that orotic acid may act directly on the enzymes involved in the synthesis and interconversion of one-carbon folic acid derivatives [172]. The protein incorporation of serine, but not of leucine or methionine, is increased in the presence of either orotic acid or vitamin B12 [173]. In addition, these two compounds also exert a similar effect on the increased formate incorporation into the RNA of liver cell fractions in chicks [174—176]. It is therefore postulated that there may be a common role of orotic acid and vitamin Bj2 at the level of the transcription process in m-RNA biosynthesis [174—176]. 

For the genetic information stored in DNA to become effective, it has to be rewritten (transcribed) into RNA. DNA only serves as a template and is not altered in any way by the transcription process. Transcribable segments of DNA that code for a defined product are called genes. It is estimated that the mammalian genome contains 30 000-40 000 genes, which together account for less than 5% of the DNA. 

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