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CoTC element downstream of the polyadenylation site in the human b-globin mRNA is a ribozyme that cleaves itself This generates a free RNA 5’-end This cleavage is required for normal transcription termination It provides an entry site for Xrn2, a 5’3’ exonuclease that loads onto the RNA and chases RNA polymerase by degrading the RNA

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RNAs containing group II introns self-splice by a pathway using an A-branched lariat intermediate, like spliceosome lariats Secondary structures of the splicing complexes involving spliceosomal systems and group II introns are very similar

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An important transcription elongation facilitator is FACT (facilitates chromatin transcription) Composed of 2 subunits: Spt16 Binds to H2A-H2B dimers Has acid-rich C-terminus essential for these nucleosome remodeling activities SSRP1 binds to H3-H4 tetramers Facilitates transcription through a nucleosome by promoting loss of at least one H2...

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Signal transduction pathways begin with a signaling molecule interacting with a receptor on the cell surface This interaction sends the signal into the cell and frequently leads to altered gene expression Many signal transduction pathways rely on protein phosphorylation to pass the signal from one protein to another This leads to signal amplific...

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Assembly of the preinitiation complex on each kind of eukaryotic promoter begins with binding of assembly factor to promoter TBP is this factor with TATA-containing class II and class III promoters If TBP is not the first bound, it still becomes part of the growing preinitiation complex and serves an organizing function Specificity of TBP depend...

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These are position- and orientation-independent DNA elements that stimulate or depress, respectively, transcription of associated genes Are often tissue-specific in that they rely on tissue-specific DNA-binding proteins for their activities Some DNA elements can act either as enhancer or silencer depending on what is bound to it

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E. coli glnA gene is an example of a prokaryotic gene depending on an enhancer for its transcription Enhancer binds the NtrC protein interacting wit polymerase bound to the promoter at least 70 bp away Hydrolysis of ATP by NtrC allows formation of an open promoter complex The two proteins interact by looping out the DNA Phage T4 late enhancer ...

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When lysogen suffers DNA damage, SOS response is induced Initial event is seen in a coprotease activity in RecA protein Repressors are caused to cut in half, removing them from l operators Lytic cycle is induced Progeny phage can escape potentially lethal damage occurring in host

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Region that binds to the ligand is an aptamer An expression platform is another module in the riboswitch which can be: Terminator Ribosome-binding site Another RNA element that affects gene expression Operates by depressing gene expression Some work at the transcriptional level Others can function at the translational level

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Compare the sedimentation of transcripts made in presence and absence of r Without r, transcripts cosedimented with the DNA template – they hadn’t been released With r present in the incubation, transcripts sedimented more slowly – they were not associated with the DNA template It appears that r serves to release the RNA transcripts from the DNA...

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