-
Categories
-
Pharmaceutical Intermediates
-
Active Pharmaceutical Ingredients
-
Food Additives
- Industrial Coatings
- Agrochemicals
- Dyes and Pigments
- Surfactant
- Flavors and Fragrances
- Chemical Reagents
- Catalyst and Auxiliary
- Natural Products
- Inorganic Chemistry
-
Organic Chemistry
-
Biochemical Engineering
- Analytical Chemistry
- Cosmetic Ingredient
-
Pharmaceutical Intermediates
Promotion
ECHEMI Mall
Wholesale
Weekly Price
Exhibition
News
-
Trade Service
the mRNA generated by transcription in primary nuclear organisms is polyseid That is, several structuresgene, using a common promoter and a common termination signal to transcription to produce an mRNA, so this mRNA molecule encodes several differentprotein . For example, the Z, Y, and A genes on lactose manipulators, transcription-generated mRNAs can be translated to produce three enzymes, semi-lactose glycosidease, through enzymes and acetyl-basedtransferase.
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 post-transcription processing modification process.
mRNA produced by transcription of a urn of urns is a monoso-inverse, i.e. an mRNA molecule is encoded as a protein molecule.
processing modification of the nuclear biomRNA, including the modification of the 5' and 3' ends, as well as the cutting of the middle part.
1. At the 5th end of the cap
mature ethyre biomRNA, the 5' end of its structure has an m7G-PPNN structure, the structure is called methyl bird 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 this kernel 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 mRNA as a starting point for translation, providing signals to the identification of mRNA by the rnapometum, which may also increase the stability of mRNA and protect mRNA from the attack of 5 exoches nucleic acidase.
2. At the 3' end
most of the posnel mRNAs have a 3' polytail (A) and a poly (A) tail of about 200bp.
polylysed (A) butchers are not encoded byDNA, but are tweed and added to the nuclei. Catalyzed by polyA polymerase, the enzyme is able to identify the free 3'-OH end of mRNA, and adds about 200 A residues.
known in recent years that there is an AATAA sequence at the 3' end of most poon genes, which is a signal of mRNA 3'-end plus polyA tail. By nuclease in this signal downstream 10-15 base off the cutting off of phosphate phosphate diesyl bonds, in polyA polymerase catalysis, in 3'-OH one by one the introduction of 100-200 A base.
questions about the function of polyA tails, 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. It is also thought that this structure has some effect on the translation efficiency of the urn mRNA, and can stabilize the mRNA structure and maintain a certain biological half-life.
3.mRNA pregenes (hnRNA)
The structural genes of the primary nucleus are continuously encoded sequences, while the energies of the urn are often fractured genes, i.e. coded one The protein molecule's >nucleotide sequence is separated by multiple insertions, and the number of inclusions in an ebony biostruct structure gene is often related to the size of the gene, for example, insulin is a very small protein, and its structural gene has only two inclusions.
some very large proteins, and there can be dozens of containing children in their structural genes. 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 inclusions, but the inclusion of subsethics is meaningless, more and more experiments have proved that there are many genes in the gene inclusions involved in gene expression regulation, in transcription, exons and inclusions are transped into hnRNA.
In the nuclei of the cell hnRNA for shearing, first under the action of nucleic acid incision enzymes to cut off the inclusions, 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 do not need to be sheared, such as α-interferon gene.
mRNA stitching, need to be in the stitching site for stitching identification of a conservative consistent order, through the analysis of more than 100 kinds of ethyrial cell genes, found that the external and inner mlicing part of the base sequence has a certain law (see Table 17-4).
17-4 contains the base order of the transcription product of the inner element at its splicing
| gene region> | "middle>Exon | Intron | Exon |
| "middle" egg white protein in the yuan 2 | UAAG GUGA | .s. s. s. s. s. s. s. > | < >
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.
mRNA splicing reaction requires the involvement of small molecule RNA in the nucleus in a complex they form with proteins called small RNA protein particles, and SnRNA is named U1, U2, U3, U4, U5, and U6RNA, respectively.
U2RNA in SnRNA is highly complementary to the UACUA sequence near the end-right splicing site of the inner organ, forming a ring structure that is identified by a specific enzyme to remove the ring structure and complete the stitching process.
the nucleus mRNA premeditation in the cutting process, can also form a cassette-like structure, in the containing sub sequence often has a branch of the adenosine residue, its 2'-OH can automatically attack the inclusion of 5' end and exon 1 connected phosphate phosphate bonds, cut open the exosome 1, and the original 3', 5'- adenosine bond connected to the two adjacent nucleotide residues.
Plus this 3', 5' - phosphate deester bond connection, there is a zip at the adenosine, has been cut off the exon 1 3'-OH attack containing the end of the exon 3' and the exon 2 between the 3', 5'-phosphate deester bond, after the key break, the inclusion in the form of a casing can be sectioned down, at this time exon 1 and exon 2 can be connected.
, regardless of the stitching process, stitching must be extremely accurate, otherwise it can lead to transmission of genetic information disorders, synthetic proteins may lose their normal function. Large areas of southern China are high-risk areas of β-thalassemia due to a hemoglobin disease caused by partial or complete inhibition of the synthesis of the β-globin chain.
experiments showed that the point ef of nucleotides in the β-globulin gene meta-1 changed the base sequence of the normal stitching site, resulting in stitching of the wrong part. Although mature mRNA can be translated, the product is not normal β-bead protein, resulting in changes in hemoglobin-level structure and function.
.
