DNA Mismatch Repair System

This article discusses the DNA mismatch repair system, which is responsible for detecting and correcting mismatches that occur during DNA replication. It explains the process of how the system recognizes and removes incorrect bases, and highlights the importance of repairing errors in the daughter strand. The article also mentions the specific proteins involved in the repair process in E. coli and provides insights into the similarities between the mismatch repair systems in eukaryotes and prokaryotes.

Answer1: Genome
The DNA mismatch repair system detect mismatches that occur during DNA replication.
Enzymes system involve in detecting mismatches works in following manner:
1. Recognises mismatched base pairs.
2. Determine the bases in which mismatch occur.
3. Remove the incorrect bases and carry out repair synthesis.
The repair must be made in the daughter polynucleotide because it is in this newly synthesized
strand that the error has occurred; the parent polynucleotide has the correct sequence. When
mismatch errors occur during replication in E. coli, it is possible to distinguish the original
strand DNA. During the period while the newly synthesized strand awaits the introduction of
methyl groups, the two strands can be distinguished.There is a delay between DNA replication
and methylation of the daughter strand, and it is during this window of opportunity that the repair
system scans the DNA for mismatches and makes the required corrections in the
undermethylated, daughter strand.
In E. coli the long patch system involves three Mut proteins, coded by the mut genes.
These mut proteins are MutH, MutL and MutS. Recognition of the sequence GATC and of the
mismatch are specialized functions of the MutH and MutS proteins, respectively.The MutH
protein cleaves the unmethylated strand on the 5' side of the G in the GATC sequence. The
combined action of DNAhelicase II and exonuclease I then removes a segment of the new strand
between the cleavage site and a point just beyond the mismatch. The resulting gap is filled in by
DNA polymerase and the nick is sealed by DNA ligase. MMR in eukaryotes and most bacteria
directs the repair to the error-containing strand of the mismatched duplex by recognizing the
strand discontinuities. Since the accumulating evidences indicate similarities in MMR system in
both human(eukaryotes) and yeast (prokaryotes) [1].
Answer2: Gene Ontology: The SGD project provides comprehensive info concerning the yeast
ordination and its genes, proteins, and different encoded options. we have a tendency to|once we|
after we} hunt for mutL factor in SGD we found that for a system for the correction of errors
during which associate incorrect base, that cannot kind chemical element bonds with the
corresponding base within the parent strand, is incorporated into the girl strand. The match repair
system promotes genomic fidelity by repairing base-base mismatches, insertion-deletion loops
and heterologies generated throughout DNA replication and recombination. consistent with GO
term twenty two genes area unit categorize on the premise of organic process [2].
Answer3: hExoI interacts directly with hMSH2 in vitro. hExoI has been incontestable to
functionally complement a yeast exo1 mutant strain, and also the truncated version of hExoI,
termed HEX1 (or hExoIa), has each fiber and double-stranded 5′ → 3′ nuclease activity in vitro .

during this study, we have a tendency to examined the interactions of hExoI with different
human MutS and MutL homologs. Characterization of the interaction regions suggests a
mechanism for recognition, signal and excision of the injury. Our results support a job for hExoI
in downstream events related to MMR and/or different metabolic processes involving MMR
enzymes [3].
Answer4: Functional predictions for by experimentation uncharacterized genes have benefited
from the inclusion of S. cerevisiae GO annotations and therefore the GO term as integral parts of
practical prediction technique that analyze microarray and protein–protein interaction
information. Not astonishingly, practical predictions mistreatment two or three GO terms
uncover details concerning the expression information additional effectively than those using
annotations from just one GO vocabulary [4]. Additionally to using over one term, define the
relationships between GO terms outlined within the GO biological process with protein–protein
interactions improves the accuracy of the annotations. More recent ways have taken an
integrated approach, combining multiple sorts of experimental information to spot the functions
of proteins
References
1. Tran, H.T., Keen, J.D., Kricker, M., Resnick, M.A. and Gordenin, D.A., 1997.
Hypermutability of homonucleotide runs in mismatch repair and DNA polymerase
proofreading yeast mutants. Molecular and Cellular Biology, 17(5), pp.2859-2865.
2. Cherry, J.M., Adler, C., Ball, C., Chervitz, S.A., Dwight, S.S., Hester, E.T., Jia, Y., Juvik,
G., Roe, T., Schroeder, M. and Weng, S., 1998. SGD: Saccharomyces genome
database. Nucleic acids research, 26(1), pp.73-79.
3. Takahashi, M., Shimodaira, H., Andreutti-Zaugg, C., Iggo, R., Kolodner, R.D. and
Ishioka, C., 2007. Functional analysis of human MLH1 variants using yeast and in vitro
mismatch repair assays. Cancer research, 67(10), pp.4595-4604.
4. Marc, P., Devaux, F. and Jacq, C., 2001. yMGV: a database for visualization and data
mining of published genome-wide yeast expression data. Nucleic acids research, 29(13),
pp.e63-e63.