NE102 Lecture Notes 2

Their correct destination question how might you

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their correct destination QUESTION: How might you identify specific nucleotide sequences that target an mRNA  for localization?
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Protein Sorting pt. 1 19:00 Mutate  Xlerk  and inject into cells and look for localization Xlerk  mRNA mutated at “CAC” sequences in the 3’ UTR failed to localize Localization of proteins to INTRACELLULAR COMPARTMENTS takes place co- & post- translationally POST-TRANSLATIONAL IMPORT Two fundamental steps Translation of proteins on “free” ribosomes Proteins are identified and imported directly into their correct compartments (nucleus &  mitochondria) QUESTION: How do cells identify proteins destined for the nucleus or for the  mitochondria? Genes evolved to encode common amino acid sequence tags that target proteins to  common compartments.  Nuclear localization signals (NLS) : Sequences that target proteins to the nucleus Were identified in studies of the transcription factor T antigen How do you examine where T antigen localize? ICC. QUESTION: How might you use this experimental design to identify the T antigen NLS? Mutate the gene and transfect to cell Pyruvate kinase = Cytoplasmic metabolic enzyme Restriction endonucleases were used to cut the T antigen NLS out and “fuse” it to  pyruvate kinase The T antigen NLS induced nuclear localization of pyruvate kinase Other nuclear proteins share one critical feature = several basic amino acids QUESTION: How do NLS’s direct nuclear import? Importins:  a family of proteins that bind NLS’s & transport proteins into nucleus QUESTION: How do importins transport proteins specifically into the nucleus? Through the nuclear pore complex
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Protein Sorting pt. 2 19:00 Localization of proteins to INTRACELLULAR COMPARTMENTS takes place after (and  sometimes during) their translation.
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Protein Sorting pt. 2 19:00 (2) Post-translational import (3) Sorting via the “secretory pathway” POST-TRANSLATIONAL IMPORT Translation of proteins on “free” ribosomes Proteins are identified and imported directly into their correct compartments (nucleus &  mitochondria) QUESTION: How do cells identify proteins destined for the nucleus? Genes evolved to encode common amino acid sequence tags that target proteins to  common compartments. Nuclear localization signals (NLS) : Sequences that target proteins to the nucleus QUESTION: How do NLS’s direct nuclear import? Importins  = a family of proteins that bind NLS’s & transport proteins into the nucleus QUESTION: How do importins transport proteins specifically into the nucleus?
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