DNA damage or UV irradiation leads to induction of synthesis of the BH3-only Puma protein which binds to Bak and Bax as well as to Bcl-2, allowing Bak and

Bax to form oligomeric pores.

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#Unit 3. Fundamental Processes

In Escherichia coli MMR system, MutL, in turn, activates MutH, an enzyme that causes an incision or nick on one strand near the site of the mismatch.

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#Unit 3. Fundamental Processes

Nicking is followed by the action of a specific helicase (UvrD) and one of three exonucleases.

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#Unit 3. Fundamental Processes

Eukaryotic cells also repair mismatches and do so using homologs to MutS (called MSH proteins for “MutS homologs”) and MutL (called MLH and PMS

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#Unit 3. Fundamental Processes

In BER, A DNA glycosylase recognizes a damaged base (in this case, a uracil) and cleaves between the base and deoxyribose in the backbone.

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n BER,  An AP endonuclease cleaves the phosphodiester backbone near the AP site

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#Unit 3. Fundamental Processes

In BER,  DNA polymerase I initiates repair synthesis from the free 3’ hydroxyl at the nick, removing (with its 5’-3’ exonuclease activity) and replacing a portion of the damaged strand.