It is the first product of the DNA transcriptionby RNA polymerase.
Micro RNAs are now widely accepted as major players in the translational control of protein synthesis.
Initiation of Transcription in Eukaryotes
The transcription of each operon is initiated at a promoter region andcontrolled by a neighboring regulatory gene (an operator which binds to arepressor or an apoinducer, to repress or induce the transcription,respectively).
Furuichi Y (1981) Allosteric stimulatory effect of S‐adenosylmethionine on the RNA polymerase in cytoplasmic polyhedrosis virus. A model for the positive control of eukaryotic transcription. Journal of Biological Chemistry 256: 483–493.
The features of eukaryotic mRNA synthesis are ..
For polynucleotide synthesis to occur, the transcription machinery needs to move histones out of the way every time it encounters a nucleosome. This is accomplished by a special protein complex called , which stands for “facilitates chromatin transcription.” This complex pulls histones away from the DNA template as the polymerase moves along it. Once the pre-mRNA is synthesized, the FACT complex replaces the histones to recreate the nucleosomes.
The termination of transcription is different for the different polymerases. Unlike in prokaryotes, elongation by RNA polymerase II in eukaryotes takes place 1,000–2,000 nucleotides beyond the end of the gene being transcribed. This pre-mRNA tail is subsequently removed by cleavage during mRNA processing. On the other hand, RNA polymerases I and III require termination signals. Genes transcribed by RNA polymerase I contain a specific 18-nucleotide sequence that is recognized by a termination protein. The process of termination in RNA polymerase III involves an mRNA hairpin similar to rho-independent termination of transcription in prokaryotes.
Termination of eukaryotic mRNA transcription is less well ..
Feoktistova K, Tuvshintogs E, Do A and Fraser CS (2013) Human eIF4E promotes mRNA restructuring by stimulating eIF4A helicase activity. Proceedings of the National Academy of Sciences of the USA 110: 13339–13344.
Fabian MR, Sonenberg N and Filipowicz W (2010) Regulation of mRNA translation and stability by microRNAs. Annual Review of Biochemistry 79: 351–379.
Transcription Initiation of Eukaryotic mRNA Coding …
Transcription Initiation of Eukaryotic mRNA ..
The entire DNA sequence necessary for thesynthesis of a functional polypeptide or RNA molecule.
and commence accurate mRNA synthesis
RNA polymerase I is dedicated to the synthesis of only one type of RNA molecule(pre-rRNA).
the synthesis of a new RNA chain using the ..
The concentration of each tag sequence is proportional to the level ofits mRNA in the original sample.
Considered the 1st part of Protein Synthesis
Following the formation of the preinitiation complex, the polymerase is released from the other transcription factors, and elongation is allowed to proceed as it does in prokaryotes with the polymerase synthesizing pre-mRNA in the 5' to 3' direction. As discussed previously, RNA polymerase II transcribes the major share of eukaryotic genes, so this section will focus on how this polymerase accomplishes elongation and termination.
and the Transcription Initiation Complex molecule slows down
Transcription in eukaryotes involves one of three types of polymerases, depending on the gene being transcribed. RNA polymerase II transcribes all of the protein-coding genes, whereas RNA polymerase I transcribes rRNA genes, and RNA polymerase III transcribes rRNA, tRNA, and small nuclear RNA genes. The initiation of transcription in eukaryotes involves the binding of several transcription factors to complex promoter sequences that are usually located upstream of the gene being copied. The mRNA is synthesized in the 5' to 3' direction, and the FACT complex moves and reassembles nucleosomes as the polymerase passes by. Whereas RNA polymerases I and III terminate transcription by protein- or RNA hairpin-dependent methods, RNA polymerase II transcribes for 1,000 or more nucleotides beyond the gene template and cleaves the excess during pre-mRNA processing.
Protein Synthesis -Translation and Regulation
Chu C and Shatkin AJ (2008) Apoptosis and autophagy induction in mammalian cells by small interfering RNA knockdown of mRNA capping enzymes. Molecular Cell Biology 19: 5829–5836.
RNA synthesis (transcription) ..
In eukaryotes, the conserved promoter elements differ for genes transcribed by RNA polymerases I, II, and III. RNA polymerase I transcribes genes that have two GC-rich promoter sequences in the -45 to +20 region. These sequences alone are sufficient for transcription initiation to occur, but promoters with additional sequences in the region from -180 to -105 upstream of the initiation site will further enhance initiation. Genes that are transcribed by RNA polymerase III have upstream promoters or promoters that occur within the genes themselves.
Initiation of influenza virus mRNA synthesis by cap‐snatching
Furuichi Y, Muthukrishnan S, Tomasz J and Shatkin AJ (1976) Mechanism of formation of reovirus mRNA 5′‐terminal blocked and methylated sequence, m7GpppGmpC. Journal of Biological Chemistry 251: 5043–5053.
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