Molbio Lecture�Tuesday

Molbio Lecture�Tuesday - Molbio LectureTuesday...

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Unformatted text preview: Molbio LectureTuesday 11/03/2008 07:43:00 Transcription factors They can interact with a first protein to make it bond to the Basil machinery (co activator/connector proteins) and help to hold the Basil machinery in place Can function from quite a distance Can change the structure of chromatin by attaching acetyl groups o the histones o Co activator that can acetylate histones cdp/p300 for histone h4 binds to ctafwhich acetylated histone h3 o When acetylated, histones allow transcription to proceed o Competing reaction mediated by histone deacetylases Remove acetyl groups and shut downs transcriptional machinery Other levels of transcriptional control Nuclear receptorsinclude steroid receptors o Glucocorticoid receptors Act by increasing glucose Activate anti-inflammatory action o Vitamin D o Androgens o Estrogens o Thyroid hormones o Enter cells easilymeet receptors in cytoplasm, bind to correct receptor, change confirmation of receptormoves to nucleusbinds to binding site in the enhancer of genes that are meant to be activated by the specific hormone Modifications of mRNAs Capping o Necessary of initiation of translation o Added through a 5-5 phosphate linkagedifferent than other linkages bc of 3 phosphate groupsadded by guanilil transferase enzyme to the end of RNA to allow translational machinery to recognize messenger RNA o If cap is removed, RNA is rapidly degraded Polyadenylation o Sequence near the 3 end of an RNA transcript: 5AAUAAA3 Recognized by a complex of proteins that bind to sequence, reach down 30 nucleotides and cleave RNA Poly-A polymerase adds a stretch of As to end of nuclease For the initiation of translation and stability of mRNA Normal control mechanism for use/degradation of mRNA If it shortens up, it is degraded Splicing o Rich Roberts/Phil Sharp o Made of exonscuts out the introns and bind the exons together Ends of introns are marked by the GTAAGT sequence at the left end and AG at the right end GT (U)-AG rule Difficult to find introns o snRNPs: protein RNA complexes that mediate splicing 1. 5 exon is separated When it is cleaved, the 2 end of RNA bonds to the 5 end of itselfrapidly degraded when floating around 2. 5 is covalently joined to the 3 end o Why splice? You can change reading frames to recycle coding regions to make 2 proteins from the same general coding region (in bacteria) Accelerates evolution by allowing to produce new proteins by exon shuffling Exons are modules of specific functions...
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Molbio Lecture�Tuesday - Molbio LectureTuesday...

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