BIOL 3510 1st Edition Lecture 5 Outline of Last Lecture I Nucleotides and the Composition of DNA II Genome III Chromosome packing IV Inside of the Nuclear Envelope Outline of Current Lecture I Intro to Transcription II Types of RNA III Bacterial Transcription IV Eukaryotic Transcription Current Lecture The Central Dogma Differences between RNA and DNA Nucleotide sugar is ribose Uses uracil instead of thymine Typically single stranded RNA molecules can fold into specific 3D shapes that have catalytic and structural functions Transcription produces an RNA molecule that is complementary to the template strand of DNA Polymerases catalyze the formation of phosphodiester bonds RNA polymerases mediate transcription Genes are transcribed by many RNA polymerases at the same time Types of RNA Produced in Cells Type of RNA Function Messenger RNAs mRNAs Code for proteins Ribosomal RNAs rRNAs Form the core of the ribosomes structure and catalyze protein synthesis microRNAs miRNAs Regulate gene expression These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute transferRNAs tRNAs Serve as adaptors between mRNA and amino acids during protein synthesis Other noncoding RNAs Used in RNA splicing gene regulation telomere maintenance and many other processes Bacterial Transcription The sigma factor subunit of RNA polymerase recognizes the promoter The DNA is unwound and transcription begins Specific sequences tell bacterial RNA polymerase where to start promoter and stop terminator transcription Eukaryotic transcription differs from prokaryotic transcription Three types of RNA polymerases transcribe different types of genes Type of Polymerase Genes Transcribed RNA polymerase I Most RNA genes RNA polymerase II All proteins including genes mRNA genes plus genes for other noncoding RNAs e g those in spicesosomes RNA polymerase III tRNA gene 5S rRNA gene Genes for many other small RNAs Transcription factors are needed to initiate transcription Initiation requires dealing with nucleosomes Eukaryotic transcription General transcription factors are required for RNA pol II initiation TFIID TPD 11 TAF subunits The TBP subunit of TFIID distorts the DNA double helix TFIIB recognizes the distorted DNA TFIIF stabilizes interaction between RNA pol II TFIID B TFIIE recruits TFIIH TFIIH unwinds DNA at start site phosphorylates RNA pol II CTD After phophorylation RNA pol II disassociates from the Tfs and enters elongation phase Eukaryotic RNAs are processed prior to export from the nucleus mRNAs are capped and polyadenylated The coding regions exons of eukaryotic genes are interrupted by introns Splicing removes the introns and is mediated splicesomes Splicesomes consist of multiple small nuclear ribonucleoproteins snRNPs which contain small nuclear RNAs snRNAs and proteins recognize specific RNA sequences Proteins initially bound to RNA pol II mediate RNA processing Alternative splicing increases protein diversity Only properly processed mRNAs are exported from the nucleus to the cytoplasm Proteins that recognize the mRNA modifications bind to the RNA and interact with the nuclear pore complex to allow export
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