BSCI-1510 Lecture Notes - Lecture 17: Nucleotide Excision Repair, Dna Repair, Dna Mismatch Repair
9 May 2016
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Document Summary
Dna repair: spontaneous alterations or lesion happen in dna and can be catastrophic, good thing for dna repair systems that can excise the damaged section, nucleotide excision repair (ner) Transcription-coupled pathway: template strands of genes that are being actively transcribed are preferentially repaired. Global genomic pathway: corrects dna strands in remainder of the genome. Tfiih, huge protein that helps initiate transcription. Xpb and xpd act as helicases and unwrap the lesioned part of the duplex in preparation for excision by a pair of endonucleases. The segment between the incisions is released and the gap is filled by dna polymerase and sealed by dna ligase: base excision repair. Removes altered nucleotides generated by reactive chemicals present in diet, ber. Initiated by dna glycosylase that recognizes alteration and removes the altered base by cleavage of the glycosidic bond holding the base to the sugar. Dna glycosylases are specific for a particular type of altered base and there are several of them.
