Processing and modification after RNA transcription.

networkRNA after transcription processing and modificationwhether primary or ceretony rRNAs are synthesized in a more complex primary transcript, and then processed into mature RNA molecules. However, the vast majority of primary nuclear bio transcription and translation are carried out simultaneously, and with the synthesis of
DNA
at the beginning of mRNA, the nucleoprotein body is attached to the mRNA and used as a template for the synthesis of
proteins
, so the mRNA of the primary nuclei cells does not have a special post-transcription process.
contrary, the transcription and translation of ethonuclear organisms are day-to-day in time and space, and the newly transcripted mRNA is a large molecular prescrole, i.e. in-nuclear unearmed RNA. Only about 10% of the hnRNA molecules are converted into mature mRNAs, and the rest are degraded during transcription processing.(i) the processing modification of mRNAthe mRNA produced by transcription in primary nuclear organisms is a polysethon, i.e. several structures
gene
, using common initiator and co-termination signal transcription to generate an mRNA, so this mRNA molecule encodes several different proteins. For example, the Z, Y, and A genes on lactose manipulators, transcription-generated mRNAs can be translated to produce three enzymes, semi-lactose glycosidease, which are transferred through enzymes and acetyl-.
there is no nuclear mold in the original nuclear organism, so transcription and translation is continuous, often transcription has not been completed, translation has begun, so the original nuclear organism transcription generated mRNA does not have a special process of transcription and post-processing modification.mRNA produced by transcription of urns of urns is monoso-inverse, i.e. an mRNA molecule is encoded as a protein molecule.processing modification of the machining of the nucleo-biological mRNA, including the modification of the 5' and 3' ends, as well as the cutting of the middle part.1. At the 5' end capmature end biomRNA, the 5' end of its structure has an m7G-PPNN structure, which is called methylbird glycoside hat. As shown in Figure 17-9. Bird glycoside is connected to the 5' end of the primary transcript by using the 5'-5' coking phosphoric acid bond.
When the 7th carbon atom on the bird glycoside is methylated to form m7G-PPNN, the hat formed at this time is called "cap 0", if the m7G-PPNmN is attached, the carbon "2" on the nuclear sugar Also methylation, the formation of m7G-PPNm, called "cap 1", if 5' end N1 and N2 in the two nuclear sugars are methylated, become m7G-PPNmPNm2, called "cap 2". It can be seen from the complexity of the formation of the true nuclear biological hat structure that the higher the degree of biological evolution, the more complex the hat structure.The importance of the -core biomRNA 5' end hat structure is that it is the necessary structure for the translation of mrNa, which signals the identification of mRNA by the rnatic glycogen, which may also increase the stability of the mRNA and protect the mRNa from 5'exoches
national acid
ases.2. At the 3' endmost of the posnel mRNA has a 3' polytail (A) and a poly (A) tail of about 200bp.polylysed (A) butcher's bar is not encoded by DNA, but is tweed and added to the nuclei. Catalyzed by polyA polymerase, the enzyme recognizes the free 3'-OH end of mRNa and adds about 200 A residues. . In recent years, it has been known that there is an AATAA sequence at one end of most of the myoker gene 3', which is the signal of the mRNa 3'-end plus polyA tail. By
nuclease
in this signal downstream 10-15 base outside the cut off phosphate phosphate phosphate bonds, in polyA polymerase catalysis, in 3'-OH one by one to introduce 100-200 A base.
questions about the function of polyA's tail, though extensively explored, are not entirely clear. It has been speculated that polyA may be related to the transfer of mRNA from the nuclei of cells to cytones, but a significant amount of mRNA without polyA butchers, such as histone mRNA, also enters the cytocyte through the nucleoblast.
also believe that this structure has some effect on the translation efficiency of the urn mRNA, and can stabilize the mRNA structure, maintaining a certain biological half-life. . 3. The splicing of mRNA pregeners (hnRNAs) the structural genes of primary nucleotides are continuous coding sequences, while the ebony genes are often fractured genes, i.e. the
nucleotides
sequences that encode a protein molecule are inserted into fragments Separated, the number of inclusions in an etonymical structure gene is often related to the size of the gene, for example, insulin is a very small protein, its structure gene has only two containing children, and some large proteins, its structural gene can have dozens of containing children. After a complex process, the internals are cut off and the encoded nucleotide fragments (Extron exons, also known as exons) are connected. The structure of the uterine organism has expressive activity of exons, but also contains non-expression activity of the inclusion of extratones, but the inclusion of subsethics is meaningless, more and more experiments have proved that there are many genes in which the inclusion of children involved in gene expression regulation, in transcription, exons and inclusions are transped into hnRNA.
In the nuclei of the cell hnRNA to cut off the inclusions, first under the action of the nucleic acid incision enzyme, and then under the action of the connective enzyme, the exon parts are connected, and become mature mRNA, this is the shearing effect, there are a few genes hnRNA does not need to be sheared, such as α-interferon gene, Figure 17-11 to the egg white protein gene as an example, introduced a typical transplication and processing process. mRNA stitching needs to have a conservative consistent order for stitching recognition at the splicing site, through the analysis of more than 100 kinds of myocyte genes, it is found that the external and endogenetic stitching part of the base sequence has a certain law.
gene region Exon Intron Exon egg white protein yuan 2 UAAG GU β GA β s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CAGUCUC Ig is contained in the sub-1 UCAG GUCA , GCAGGGGC SV40 virus early T
antigen
UAAG GUAA , UUAGAUUC
table line of the base of the stitching recognition plays an important role, such as the rabbit's β-bead protein stitching site GT to AT, the stitching reaction is affected.
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