microRNA

Examples of microRNA in the following topics:

• Cancer and Post-Transcriptional Control

  • Recently, several groups of researchers have shown that specific cancers have altered expression of microRNAs (miRNAs) . miRNAs bind to the 3' UTR or 5' UTR of RNA molecules to degrade them.
  • Overexpression of these miRNAs could be detrimental to normal cellular activity.
  • An increase in many miRNAs could dramatically decrease the RNA population leading to a decrease in protein expression.
  • Overexpression of miRNAs could be detrimental to normal cellular activity because miRNAs bind to the 3' UTR of RNA molecules to degrade them.
  • Specific types of miRNAs are only found in cancer cells.

• 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.

• Verrucomicrobia

  • Support for this superphylum has been found by examining the RNA polymerase protein RpoB.
  • rpoB is the gene that encodes the β subunit of bacterial RNA polymerase.
  • Cavalier-Smith has postulated that the Verrucomicrobia belong in the clade Planctobacteria in the larger clade Gracilicutes. 16S rRNA data corroborate that view.
  • RNA polymerase II (also called RNAP II and Pol II) is an enzyme found in eukaryotic cells.
  • It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA.

• Initiation of Transcription in Eukaryotes

  • RNA polymerase I synthesizes all of the rRNAs except for the 5S rRNA molecule.
  • RNA polymerase II is located in the nucleus and synthesizes all protein-coding nuclear pre-mRNAs.
  • RNA polymerase II is responsible for transcribing the overwhelming majority of eukaryotic genes, including all of the protein-encoding genes which ultimately are translated into proteins and genes for several types of regulatory RNAs, including microRNAs (miRNAs) and long-coding RNAs (lncRNAs).
  • This polymerase transcribes a variety of structural RNAs that includes the 5S pre-rRNA, transfer pre-RNAs (pre-tRNAs), and small nuclear pre-RNAs.
  • Not all miRNAs are transcribed by RNA Polymerase II, RNA Polymerase III transcribes some of them.

• DNA and RNA

  • This intermediary is the messenger RNA (mRNA).
  • Other types of RNA—like rRNA, tRNA, and microRNA—are involved in protein synthesis and its regulation.
  • DNA and RNA are made up of monomers known as nucleotides.
  • DNA contains A, T, G, and C whereas RNA contains A, U, G, and C.
  • The pentose sugar in DNA is deoxyribose and in RNA it is ribose.

• 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.
  • In bacteria, multiple tRNAs are often transcribed as a single RNA.
  • Describe how pre-rRNAs and pre-tRNAs are processed into mature rRNAs and tRNAs.

• Small Regulatory RNAs

  • Small regulatory RNAs encompass a specific class of RNAs that affect gene regulation.
  • Antisense RNAs are used to bind to complementary mRNAs and inhibit protein translation.
  • The antisense RNAs are categorized as small regulatory RNAs due to their small size.
  • Small regulatory RNAs encompass many RNAs involved in house-keeping processes as well.
  • The antisense RNA can bind to the mRNA and inhibit translation.

• Sources of Essential Nutrients

  • There are two categories of essential nutrients: macro-nutrients (which are needed in large amounts) and micro-nutrients (which are needed in trace or small amounts).
  • Micro-nutrients help enzyme function and maintain protein structure.
  • Another essential nutrient, nitrogen, is part of the structure of protein, DNA, RNA, and ATP.

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

• Micro-hydro power stations

  • Micro-hydro stations use natural water fl ows from rivers and streams to produce hydroelectricity.
  • Micro-hydro stations are particularly viable in areas where industrialists during the 18th and 19th centuries built now-unused weirs to turn water wheels that powered looms and other industrial machinery.
  • To read more about micro-hydro stations visit www.energysavingtrust.org.uk/Generate-your-own-energy/Hydroelectricity or www.absak.com/library/micro-hydro-power-systems.