Mismatch Excision Repair in Eukaryotes

DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of bases that can arise during DNA replication and recombination, as well as repairing some forms of DNA damage.
Mismatch repair is strand-specific. During DNA synthesis the newly synthesised (daughter) strand will commonly include errors. In order to begin repair, the mismatch repair machinery distinguishes the newly synthesised strand from the template (parental). In gram-negative bacteria, transient hemimethylation distinguishes the strands (the parental is methylated and daughter is not). However, in other prokaryotes and eukaryotes, the exact mechanism is not clear. It is suspected that, in eukaryotes, newly synthesized lagging-strand DNA transiently contains nicks (before being sealed by DNA ligase) and provides a signal that directs mismatch proofreading systems to the appropriate strand. This implies that these nicks must be present in the leading strand, and evidence for this has recently been found.[3] Recent work has shown that nicks are sites for RFC-dependent loading of the replication sliding clamp, proliferating cell nuclear antigen (PCNA), in an orientation-specific manner, such that one face of the donut-shape protein is juxtaposed toward the 3'-OH end at the nick. Loaded PCNA then directs the action of the MutLalpha endonuclease to the daughter strand in the presence of a mismatch and MutSalpha or MutSbeta.
Examples of mismatched bases include a G/T or A/C pairing (see DNA repair). Mismatches are commonly due to tautomerization of bases during DNA replication. The damage is repaired by recognition of the deformity caused by the mismatch, determining the template and non-template strand, and excising the wrongly incorporated base and replacing it with the correct nucleotide. The removal process involves more than just the mismatched nucleotide itself. A few or up to thousands of base pairs of the newly synthesized DNA strand can be removed.

[@umerfarooqbiology7083]

I like it the repair mismatch animation please upload the series of DNA repair I hope you give us great knowledge....thanks shabir hussain..

[@michaeleisenberg7867]

What happens if it's the opposite strand that has the incorrect nucleotide?

[@hussainbiology]

Parental strand will never become one if not repaired at first place..
All daughter strands will become parental once repaired after Replication

[@michaeleisenberg7867]

@@hussainbiology I think I understand. During DNA replication the parental strand is methylated. It is then copied. It is assumed that the parental strand is correct. With the mismatch repair proteins any mistake in the daughter strand is repaired.
🧬 ✅
Shabir, Another solid video! Thank you so so much. I don't know if you have the energy to do a deep dive into just one of those proteins and show the active site and how any mineral co-factors are added during their construction. The molecular 🔬stuff is very interesting.
👏👏👏👏👏

[@hussainbiology]

@@michaeleisenberg7867 surely i will do

[@udaysharma2802]

Mahakal bless you my son keep doing jai shree ram