cells. What are the possible mechanisms in regulating the expression of this gene? O Transcription: focusing on transcription initiation described on p 222 of the text book. (5 points) 2 Processing: 5,capping(addition of a m'G to the 5'end of the rna pol II transcript catalyzed by mRNA guanyltransferase/capping enzyme )(1.5 point), intron splicing(removal of intron by splicesome that contains 5 snRNAs and many proteins. First step-cleavage at 5 splice site and the conserved A being linked to the 5'-end of the intron, second step-3'cleavage and exon ligation) (2 points), 3'cleavage and polyadenylation(First-assembly of the recognition complex on the polyadenylation site, second-poly (A) polymerase/PAP cleaves the transcript at this site, third -PAP adds up to 250 A residues to the 3'end of the transcript)(1.5 point) Translation: Initiation, elongation and termination(p276, 278)(5 points) 4 Regulation: Firstly, regulation can occur at the transcription level, for example, through interaction of the transcription factors with the promoter or URE to activate or repress the transcription(2.5 point ) Secondly, regulation can occur at the post-transcription level, for example, alternative transcription or alternative poly (A) site(2.5 points) 2 (20 points): A bacterium is found to metabolize a rare sugar produced by a plant that the is, if you want to finish this course with a satisfied score, you must figure out the roblem bacteria grow on. However, the bacteria prefer glucose as the energy source. The regulatory mechanism that the bacteria used to determine the sugar choice use northern blot to analyze the expression of fun3 and use dN A footprinting to analye The gene involving in the rare sugar metabolism has been identified as fun3. You c the binding of proteins to the control elements of fiun3 gene. The following table shows the experimental results Glucose Rare sugar Levels of Binding of proteins presence presence fun3 RNA Protein a binds to the promoter region Protein C binds upstream of the promoter Protein a binds to the promoter region ++ Protein b binds to the promoter region Protein C binds upstream of the promoter Protein b binds to the promoter region Questions 1. Please propose a mechanism to explain the above results. You should focus on the question"How does the expression of fin3 gene is tightly regulated so that it is only highly expressed when the rare sugar is the only carbon source". You must answer what proteins A, B and C are( 8 points) Protein A-repressor, protein B-RNA polymerase, protein C-CRP/CAPcells. What are the possible mechanisms in regulating the expression of this gene? ① Transcription: focusing on transcription initiation described on p222 of the text book. (5 points) ② Processing: 5’ capping (addition of a m7G to the 5’ end of the RNA pol II transcript catalyzed by mRNA guanyltransferase/capping enzyme ) (1.5 point), intron splicing (removal of intron by splicesome that contains 5 snRNAs and many proteins. First step- cleavage at 5’ splice site and the conserved A being linked to the 5’-end of the intron, second step-3’cleavage and exon ligation) (2 points), 3’cleavage and polyadenylation (First-assembly of the recognition complex on the polyadenylation site, second-poly(A) polymerase/PAP cleaves the transcript at this site, third- PAP adds up to 250 A residues to the 3’end of the transcript) (1.5 point). ③ Translation: Initiation, elongation and termination (p276, 278) (5 points) ④ Regulation: Firstly, regulation can occur at the transcription level, for example, through interaction of the transcription factors with the promoter or URE to activate or repress the transcription (2.5 point). Secondly, regulation can occur at the post-transcription level, for example, alternative transcription or alternative poly(A) site (2.5 points). 2 (20 points): A bacterium is found to metabolize a rare sugar produced by a plant that the bacteria grow on. However, the bacteria prefer glucose as the energy source. The problem is, if you want to finish this course with a satisfied score, you must figure out the regulatory mechanism that the bacteria used to determine the sugar choice. The gene involving in the rare sugar metabolism has been identified as fun3. You can use northern blot to analyze the expression of fun3 and use DNA footprinting to analyze the binding of proteins to the control elements of fun3 gene. The following table shows the experimental results Glucose presence Rare sugar presence Levels of fun3 RNA Binding of proteins - - - Protein A binds to the promoter region Protein C binds upstream of the promoter + - - Protein A binds to the promoter region - + +++ Protein B binds to the promoter region Protein C binds upstream of the promoter + + + Protein B binds to the promoter region Questions: 1. Please propose a mechanism to explain the above results. You should focus on the question “How does the expression of fun3 gene is tightly regulated so that it is only highly expressed when the rare sugar is the only carbon source”. You must answer what proteins A, B and C are. (8 points) Protein A-repressor, protein B-RNA polymerase, protein C-CRP/CAP