messenger RNA

Examples of messenger RNA in the following topics:

• Antisense Agents

  • Antisense agents are short oligonucleotides that bind to target messenger RNA and inhibit protein synthesis.
  • Antisense agents are synthetic, single-stranded short sequences of DNA bases designed to hybridize to specific sequences of messenger RNA (mRNA) forming a duplex .
  • This DNA-RNA coupling attracts an endogenous nuclease, RNase H that destroys the bound RNA and frees the DNA antisense to rehybridize with another copy of mRNA.
  • When this agent binds to the pathogen DNA or messenger RNA, the biosynthesis of target proteins is disrupted.
  • Therefore, there are at least two ways in which antisense agents act to effectively reduce the amount of pathogenic protein being synthesized - RNase H based degradation of RNA and prevention of ribosomal assembly and translation.

• Northern Blots

  • Northern blots allow investigators to determine messenger RNA molecular weight and sample content.
  • The Northern blot is a technique used in molecular biology research to study gene expression in a sample, through detection of RNA (or isolated messenger RNA ).
  • The major difference is that RNA, rather than DNA, is analyzed in the Northern blot.
  • Eukaryotic mRNA can then be isolated through the use of oligo (dT) cellulose chromatography to isolate only those RNAs with a poly(A) tail.
  • RNA samples are then separated by gel electrophoresis.

• Unsticking Stuck Ribosomes

  • As a result it cannot eject the mRNA.
  • The proteins which freed the ribosome remain with the mRNA which targets the nonstop mRNA for recognition by RNA degradation pathway.
  • Trans-translation is a recently discovered pathway in E. coli, although it is not completely understood, it involves Transfer-messenger RNA (abbreviated tmRNA) which is a bacterial RNA molecule with dual tRNA-like and messenger RNA-like properties.
  • Subsequently, the ribosome moves from the 3' end of the truncated messenger RNA onto the tmRNA where it translates the codons of the tmRNA until the tmRNA stop codon is encountered.
  • A ribosome with its RNA binding sites, designated E, P, and A, is stuck near the 3' end of a broken mRNA.

• Ribosomes

  • The purpose of the ribosome is to translate messenger RNA (mRNA) into proteins with the aid of tRNA.
  • The purpose of the ribosome is to translate messenger RNA (mRNA) to proteins with the aid of tRNA.
  • One is for the mRNA; the other two are for the tRNA.
  • The binding sites for tRNA are the A site, which holds the aminoacyl-tRNA complex, and the P site, which binds to the tRNA attached to the growing polypeptide chain .
  • The 50S subunit contains the 23S and 5S rRNA while the 30S subunit contains the 16S rRNA.

• The Central Dogma: DNA Encodes RNA and RNA Encodes Protein

  • The central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein.
  • If the transcribed gene encodes a protein, the result of transcription is messenger RNA (mRNA), which will then be used to create that protein in the process of translation.
  • Transfer RNA, or tRNA, translates the sequence of codons on the mRNA strand.
  • Instructions on DNA are transcribed onto messenger RNA.
  • Ribosomes are able to read the genetic information inscribed on a strand of messenger RNA and use this information to string amino acids together into a protein.

• RNA Splicing

  • Alternative splicing can occur due to the different ways in which an exon can be excluded from or included in the messenger RNA.
  • The pattern of splicing and production of alternatively-spliced messenger RNA is controlled by the binding of regulatory proteins (trans-acting proteins that contain the genes) to cis-acting sites that are found on the pre-RNA.
  • Proteins that are translated from alternatively-spliced messenger RNAs differ in the sequence of their amino acids which results in altered function of the protein.
  • The splicing of messenger RNA is accomplished and catalyzed by a macro-molecule complex known as the spliceosome.
  • Equally as important are the silencers and enhancers that are found on the messenger RNAs, also known as cis-acting sites.

• Viral Replication and Gene Expression

  • Replication also involves synthesis of viral messenger RNA (mRNA) from "early" genes (with exceptions for positive sense RNA viruses), viral protein synthesis, possible assembly of viral proteins, then viral genome replication mediated by early or regulatory protein expression.
  • Viruses that replicate via RNA intermediates need an RNA-dependent RNA-polymerase to replicate their RNA, but animal cells do not seem to possess a suitable enzyme.
  • Therefore, this type of animal RNA virus needs to code for an RNA-dependent RNA polymerase.
  • No viral proteins can be made until viral messenger RNA is available; thus, the nature of the RNA in the virion affects the strategy of the virus: In plus-stranded RNA viruses, the virion (genomic) RNA is the same sense as mRNA and so functions as mRNA.
  • One of these includes RNA-dependent RNA polymerase (RNA replicase), which copies the viral RNA to form a double-stranded replicative form, in turn this directs the formation of new virions.

• RNA Regulation and Antisense RNA

  • Antisense RNAs are single-stranded RNA molecules that can bind and inhibit specific mRNA translation to protein.
  • There are specific types of RNA molecules that can be utilized to control gene regulation, including messenger RNAs (mRNAs), small RNAs such as microRNAs and lastly, antisense RNAs.
  • The following is a brief overview of antisense RNAs and their role in RNA regulation.
  • Antisense RNAs are single-stranded RNA molecules that exhibit a complementary relationship to specific mRNAs.
  • The antisense RNA can physically pair and bind to the complementary mRNA, thus inhibiting the ability of the mRNA to be processed in the translation machinery.

• Types of RNA

  • This intermediary is the messenger RNA (mRNA).
  • Instead, another type of RNA called transfer RNA (tRNA) needs to translate the information from the mRNA into a usable form.
  • The tRNA attaches to the mRNA, but with the opposite base pairings.
  • The ribosome acts like a giant clamp, holding all of the players in position, and facilitating both the pairing of bases between the messenger and transfer RNAs, and the chemical bonding between the amino acids.
  • These subunits do not carry instructions for making a specific proteins (i.e., they are not messenger RNAs) but instead are an integral part of the ribosome machinery that is used to make proteins from mRNAs.

• Processing of tRNAs and rRNAs

  • The tRNAs and rRNAs are structural molecules that have roles in protein synthesis; however, these RNAs are not themselves translated.
  • One contains just the pre-rRNA that will be processed into the 5S rRNA; the other spans the 28S, 5.8S, and 18S rRNAs.
  • The 60S subunit is composed of the 28S rRNA, 5.8S rRNA, 5S rRNA, and 50 proteins.
  • The anticodon is a three-nucleotide sequence, unique to each different tRNA, that interacts with a messenger RNA (mRNA) codon through complementary base pairing.
  • Describe how pre-rRNAs and pre-tRNAs are processed into mature rRNAs and tRNAs.