2 History mRNA and tRNA worked out in the 1960s Purification of RNA lead to 23S, 16S, and 4S species and accounted for 85% of all RNAtRNA accounted for about 15% of all RNAHybridization experiments did not match DNAmRNA accounts for only 1-4% of RNA
3 Types of RNAmRNAtRNArRNAsnRNAsnoRNAsiRNAmicroRNA
4 Primary RNA mRNA (messenger RNA) rRNA (ribosomal RNA) Transcribed from DNAIs then translated into proteinrRNA (ribosomal RNA)Necessary for helping ribosomes make protein (catalysis)tRNA (transfer RNA)Mediates amino acid recognition with codons
5 Other RNA snRNA – small nuclear snoRNA – small nucleolar microRNA – microsiRNA – short interferingThese RNA species have a variety of functions and not all of them have been worked out yet.
6 RNA and RfamPfam is a database we discussed to determine groups of proteinsRfam is a similar database for families of RNA
7 tRNA and folding tRNA have a unique fold There are multiple websites to determine RNA folding
8 Ribosomal RNA Has a structural and functional role in ribosomes Prokaryotes: 70S which is 30S & 50S, which is 16S, 23S, 5SEukaryotes: 80S which is 45S which is 18S, 28S, and 5.8S
9 snRNA Found in nucleus Involved with splicing and telomer maintenance 5 classes U1, U2, U4, U5, U6
10 snoRNA Modify both rRNA and snRNA 2 Classes C/D Box – methylate rRNA H/ACA Box – convert uridine to peudouridine in rRNA
11 miRNA Recent discovery Small approximately 22 nucleotides Function to down regulate protein expression.
12 RNAi (siRNA) Double stranded RNA Small, artificial Degradation by RISC and DicerProtective mechanism for plants and animals
13 mRNA Coding RNA Central Dogma “one gene – one protein” No longer validAlternative splicing, regulation, introns, etc.Altered expression by:Region, development, environment, disease, gene activity
14 mRNA Key research areas mRNA expression database There is a DNA database, but is an mRNA database equally good?Potential problems with and mRNA databaseHow to measure mRNA expression
16 est database How to study mRNA Highly unstable, need to make cDNA Turn mRNA into DNA with reverse transcriptaseClone into a vectorSequnce (this is called an express sequence tag EST)ESTs can be isolated from specific cells at specific times under specific conditions.This can aid in finding when types of proteins MAY be expressed