Algae, Tree, Herbs, Bush, Shrub, Grasses, Vines, Fern, Moss, Spermatophyta, Bryophyta, Fern Ally, Flower, Photosynthesis, Eukaryote, Prokaryote, carbohydrate, vitamins, amino acids, botany, lipids, proteins, cell, cell wall, biotechnology, metabolities, enzymes, agriculture, horticulture, agronomy, bryology, plaleobotany, phytochemistry, enthnobotany, anatomy, ecology, plant breeding, ecology, genetics, chlorophyll, chloroplast, gymnosperms, sporophytes, spores, seed, pollination, pollen, agriculture, horticulture, taxanomy, fungi, molecular biology, biochemistry, bioinfomatics, microbiology, fertilizers, insecticides, pesticides, herbicides, plant growth regulators, medicinal plants, herbal medicines, chemistry, cytogenetics, bryology, ethnobotany, plant pathology, methodolgy, research institutes, scientific journals, companies, farmer, scientists, plant nutrition
Select Language:
 
   
 
 
Can't find? Try Deep Search with ePlantScience.com  
 
Share |
 
   
Main Menu
If navigation gets difficult, please click the main subject or sitemap to get the list of sub-categories
 
 
 
 
 
Related websites
 
 
 
 
 
 
 
 
Section: Genetics » Expression of Gene » RNA Processing
 
 
If you like this page, please click:  
 
 
  Ribozymes
 
     
 
Content
⇒ Expression of Gene : Protein Synthesis 3.  RNA Processing (RNA Splicing, RNA Editing and Ribozymes)
⇒ Addition of caps (m7G) and tails (polyA) for mRNA
⇒ Addition of methylated cap at the 5' end
⇒ Polyadenylation and the generation of 3' end
⇒ RNA splicing
⇒ Self-splicing of group I introns
⇒ Splicing of group II introns
⇒ Splicing of eukaryotic hnRNA through spliceosomes/snurposomes
⇒ Splicing of introns using RNA maturases or endonucleases
⇒ Yeast tRNA splicing by cutting and rejoining
⇒ Trans-splicing of transcripts in chloroplasts and mitochondria
⇒ Constitutive vs. alternative Splicing
⇒ RNA Editing and Guide RNA
⇒ Ribozymes 
Ribozymes (RNA Splicing, DNA Cleavage and RNA Amplification)
Till very recently, enzymatic catalysis was thought to be the exclusive domain of proteins. As shown above in this section, only in recent years it was shown that RNA molecules can cut, splice and assemble themselves without any outside help, thus extending the range of chemistry of enzymes. These RNA molecules working as enzymes, were called ribozymes. It has also been shown that enzymes can also be synthesized chemically, and are then described as chemzymes. For the work on RNA molecules working as ribozymes, two scientists (Thomas R. Cech of- University of Colorado, Boulder and Sidney Altaian of Yale University) were awarded Nobel Prize in 1989. This discovery of RNA molecules working as enzymes has also changed our thinking about origin of life. It is now believed that four billion years ago Earth was an 'RNA world' in which RNA molecules carried out all the processes of life without the help of either protein or DNA.

The discovery of ribozymes can be traced back to 1982, when Thomas Cech, was trying to understand how 'sequences' (including sequences derived from introns) are spliced out of RNA molecules during processing of hnRNA into mRNA, or precursor rRNA into rRNA in Tetrahymena. The discovery was made when it was found that removal of proteinaceous enzymes one by one from a cell free system did not alter the splicing ability of pre-ribosomal RNA. However, these RNA molecules acted only on themselves, not on other molecules. Later in 1983 and 1984, Sidney Altman, using ribonuclease P1 (it consists of RNA + protein and is E. coli RNA processing endonuclease for splicing of tRNA), demonstrated that catalytic activity of ribonuclease P1 resided only in RNA subunit, and protein only helped RNA to perform the enzymatic function. Self cleavage of viroid RNAs or virusoids (satellite RNAs) and catalytic activity of RNAase are other examples of ribozymes. Subsequently it was shown that ribozymes may also bring about (i) cleavage of DNA molecules, and (ii) selective amplification of RNA molecules.
 
     






     
     
 
 
     
 
Copyrights 2009 © ePlantScience.com