What Type Of Dna Error Is Repaired By The Dna Mismatch Repair System

The main difference  between mismatch repair and nucleotide excision repair is that mismatch repair (MMR) is responsible for the removal of base mismatches and small-scale insertion/deletion loops introduced during Deoxyribonucleic acid replication, whereas nucleotide excision repair (NER) is responsible for the removal of a variety of DNA damages that occur due to ultraviolet radiations.  Furthermore, cells undergo mismatch repair immediately after DNA synthesis while cells undergo nucleotide excision repair if Dna gets damaged.

Mismatch repair and nucleotide excision repair are ii mechanisms which prevent mutations and other permanent changes in the DNA  sequence.

Key Areas Covered

1. What is Mismatch Repair
     – Definition, Process, Importance
2. What is Nucleotide Excision Repair
     – Definition, Procedure, Importance
iii. What are the Similarities Between Mismatch Repair and Nucleotide Excision Repair
     – Outline of Common Features
4. What is the Difference Between Mismatch Repair and Nucleotide Excision Repair
     – Comparison of Central Differences

Fundamental Terms

Deoxyribonucleic acid Impairment, Deoxyribonucleic acid Repair, Mismatch Repair (MMR), Nucleotide Excision Repair (NER), Replication Errors

What is Mismatch Repair

Mismatch repair (MMR) is a DNA repair machinery that occurs but after Dna replication. Therefore , the main objective of this mechanism is to remove and replace mispaired bases, which are not fixed by proofreading. Moreover, it detects and corrects small insertions and deletions that occur due to the slips of the Dna polymerase.

Figure one: Mismatch Repair Machinery

Usually, the three proteins in the Eastward. coli mismatch repair system are MutS , MutL , and MutH . On the other hand, eukaryotes contain only the homologous of MutS  and MutL . In humans, MutS -homologous heterodimer, MSH2- MSH6 binds to the mismatch while MSH2-MSH6 and MSH2-MSH3 can bind to the insertions/deletions loop. Then, the newly-synthesized strand is degraded, removing the mismatch past the activity of EXO1. After that, resynthesis  of DNA and ligation complete the mismatch.

What is Nucleotide Excision Repair

Nucleotide excision repair (NER) is a DNA repair mechanism to remove and replace damaged nucleotides. Generally, this mechanism detects and corrects Deoxyribonucleic acid damages, which distort DNA double helix. That is; this pathway detects nucleotides and modifies with bulky chemic groups fastened to DNA such as chemicals in cigarette smoke. Furthermore, the nucleotide excision repair pathway fixes Dna amercement caused past UV radiation. Hither, UV radiation makes thymine and cytosine bases to react with their adjacent nucleotides. Yet, the resultant bonds distort the double helix, causing errors in Dna replication. Here, the most common type of these bonds are the thymine dimers, consisting of two thymine nucleotides reacted together.

Figure ii: Nucleotide Excision Repair

Moreover, the two subpathways of nucleotide excision repair are global genome repair (GGR), which repair amercement in the overall genome, and transcription-coupled repair (TCR), which specifically repair the transcribed strand of active genes. However, these two pathways use different factors for the initial recognition step. After that, the recruiting transcription factor, TFIIH has 2 domains with helicase action of opposite polarity to unwind the Deoxyribonucleic acid around the lesions. Then, the secondly binding transcription factors cut the harm from its three′ and 5′ ends. From that, a 24-32 nucleotides-long fragment is released. Finally, the repair is completed by DNA synthesis and ligation.

Similarities Between Mismatch Repair and Nucleotide Excision Repair

• Mismatch repair and nucleotide excision repair are two types of DNA repair mechanisms.
• The primary function of them is to forestall mutations and other permanent changes in the Deoxyribonucleic acid sequence.
• Enzymes acquit out both processes.

Difference Between Mismatch Repair and Nucleotide Excision Repair

Definition

Mismatch repair (MMR) refers to a Dna repair organization whereby one fellow member of a mismatched pair of bases is converted to the ordinarily matched base while nucleotide excision repair (NER) refers to the main pathway used by mammals to remove bulky DNA lesions such equally those formed past UV calorie-free.

Significance

Cells undergo mismatch repair immediately afterwards Dna synthesis while cells undergo nucleotide excision repair with the occurrence of DNA amercement.

Type of Repair

Mismatch repair replaces mismatches and insertion/deletion loops, which are non repaired by proofreading while nucleotide excision repair replaces DNA damages formed by UV radiations or chemicals in the cigarette fume.

Excision by

Exonuclease 1 excises mismatched Dna in the mismatch repair mechanism while the transcription factors, XPG and XPF-ERCC1 excise the damaged DNA in the nucleotide excision repair mechanism.

Conclusion

Mismatch repair is the mechanism of Deoxyribonucleic acid repair, replacing the mismatches and insertion/deletion loops incorporated during DNA replication. Generally, these mismatches are the escaped ones during proofreading. On the other mitt, nucleotide excision repair is another mechanism of Dna repair, which supercede the damaged Dna by UV radiation. Therefore, mismatch repair occurs simply after Dna replication. All the same, nucleotide excision repair mechanisms occur with the occurrence of DNA damages. The main office of both mechanisms is to prevent mutations and other permanent changes in DNA. Thus, the master difference betwixt mismatch repair and nucleotide excision repair is the type of repair.

 References:

i. Bit, O. "Dna Repair."Journal of Cell Science, vol. 117, no. four, 2004, pp. 515–517., doi:10.1242/jcs.00952.

Paradigm Courtesy:

1. "DNA mismatch repair Ecoli" By Kenji Fukui (CC By 4.0) via Eatables Wikimedia
two. "Nucleotide Excision Repair-journal.pbio.0040203.g001" Past Jill O. Fuss, Priscilla Yard. Cooper (CC BY 2.5) via Eatables Wikimedia

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