11 Transcription Process Initiation, elongation and termination Structural features of a gene RNA polymerase Post transcriptional modification of mRNA Inhibitory drugs Define transcription Compare the process of transcription with that of DNA replication. Distinguish between the coding and template strand of DNA Describe the signals necessary for transcription Describe a promoter in terms of Position in a gene Numbering of nucleotides Sequence elements Bound proteins Describe the process of transcriptional initiation in terms of The effect on DNA structure The function of the sigma subunit Transcriptional regulation Distinguish between positive and negative forms of transcriptional control Describe the process of transcriptional termination both rho dependent and independent Identify the function of each RNA polymerase of eukaryotes Describe the structure of RNA polymerase II Describe how RNA polymerase II recognizes a promoter Describe two functions of TFIIH Describe the position and function of the TATA box Describe how the terminal nucleotide of a mature eukaryotic mRNA is generated Describe the mechanism of action of drugs that inhibit transcription including Actinomycin D, Rifampicin and Alpha amanitin.
DNA/RNA distinction – vicinal hydroxyls, RNA should be unstable in order to exercise control
Promoter includes sequence elements that bind RNA polymerase. Other control elements may be included within the promoter region that go by other names, such as operator Consensus sequences reflect evolutionary origin and also commonality in control. Two genes that are both needed under one set of circumstances may have very similar sequences in their promoters. This means their genes would transcribe RNA at similar times all other factors being equal.
Consensus sequences help locate where the subunits of RNA polymerase bind. Note AT rich region near where transcription bubble begins Torsion opens the local sequence at the AT rich region permitting sigma to bind and the helix to open near the start of transcription Consensus at –10 for proks resembles same for euks.
Sigma is carried by the holoenzyme, it does not locate the –10 and –35 regions on its own. RNA pol scans duplex DNA until a consensus sequence is reached that both the core enzyme and sigma recognize. They halt and form a closed complex. Then the duplex unwinds and an open complex forms – this Is the melted form with an initial bubble. Sigma is released and the core enzyme begins to polymerize at the +1 nucleotide
CAP binds DNA and locates a binding site for RNA polymerase. Increases eficiency of promotion. cAMP made in response to low glucose. Low glucose inacivates a negative control on adenylate cyclase. This makes cAMP and this binds the CAP binding site on the lac gene promoter. Lac is involved in converting lactose into galactose and glucose. Mutational effects?
To describe how an aminoacyl tRNA synthetase recognizes its cognate tRNA To describe the ribosomal structure of both prokaryotes and eukaryotes in terms of the ribosomal subunits and their rRNA’s To describe the requirements of initiation, elongation and termination in terms of Necessary factors Behavior of the ribosomal subunits Sequential steps of each process To differentiate between Prokaryotic and Eukaryotic protein synthesis
