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Messenger ribonucleic acid (mRNA) is used in protein synthesis in animals and plants. Precursor mRNA, or pre-mRNA, is the first transcript from a gene that codes proteins. Sometimes called immature mRNA, it is basically mRNA that has yet to be spliced. Pre-mRNA is an important part of the process that copies the common macromolecule DNA, which contains the genetic information for living organisms.
As part of the ongoing process of ribonucleic acid (RNA) production, pre-mRNA exists for only a brief period of time. It is the phase between a gene that has been transcribed into mRNA and the protein into which it will be translated. Splicing removes unnecessary parts so that it can become mRNA.
The main elements involved in splicing are introns, exons and specific enzymes. Pre-mRNA contains both introns and exons. Introns are sections that do not contain information necessary for coding proteins. The introns must be removed through splicing to produce a functional mRNA molecule containing only exons. Exons contain the information that will then be used in protein production.
Enzymes perform a sort of cut-and-paste function. They form a spliceosome made of ribonucleoproteins and other proteins. The spliceosome cuts the introns out of the pre-mRNA sequence and then connects the remaining exons so that there are no gaps in the code. Introns tend to be much longer than exons, so a strand will be significantly longer than the RNA strand that will result after splicing.
This process occurs within the cell nucleus and must be very precise. Any disruption in the splicing process can cause or modify diseases in the human body. Viruses such as the influenza virus have been known to interfere with or even inhibit pre-mRNA splicing, which then inhibits the formation of necessary proteins. Binding proteins are also factor in controlling and regulating pre-mRNAs. They can trigger significant changes that then activate other processes.
Genes produce pre-mRNA, which has the same components as mRNA, such as phosphates and ribose sugar. It also contains the nucleobases uracil, adenine, guanine and cytosine. Successful translation of pre-mRNA into RNA enables RNA to move outside of the nucleus, where it is translated into protein. RNA is a single-stranded molecule that helps create double-stranded DNA.
Molecular biologists have explored ways to manipulate pre-mRNA to affect gene expression and cloning processes. Splicing occurs naturally within cells. It also can be controlled in a laboratory.