GO:0032137 guanine/thymine mispair binding

Guanine/thymine mispair binding (GO:0032137) is a molecular function that describes the selective interaction of a protein with double-stranded DNA containing a G/T mispair. This activity is central to DNA mismatch recognition and repair pathways that maintain genomic integrity. The QuickGO definition states that it is the binding to a double-stranded DNA region containing a G/T mispair, and it is classified under the molecular_function aspect of the Gene Ontology. Researchers study this term because G/T mispairs are common mutagenic lesions that, if unrepaired, can lead to transition mutations and genome instability. Understanding which proteins bind G/T mispairs and how they do so is essential for mechanistic studies of DNA repair and for interpreting cancer genome data. The term is often used in annotation pipelines to describe proteins such as mismatch repair factors and DNA glycosylases that initiate repair at G/T sites. In this article, we review the definition, biological context, key genes, and experimental approaches for studying guanine/thymine mispair binding, with a focus on how CRISPR-based models can be used to test gene function.

In our own words, guanine/thymine mispair binding (GO:0032137) is the activity of a protein or protein complex that specifically recognizes and binds to a double-stranded DNA molecule in which a guanine base is paired with a thymine base instead of its normal cytosine partner. This binding event is a molecular recognition step that can initiate downstream processes such as DNA repair, mismatch correction, or transcriptional regulation. The term is defined in QuickGO as binding to a double-stranded DNA region containing a G/T mispair, and it is a child of the broader DNA binding term. It is important to note that this term describes the binding activity itself, not the catalytic steps that follow.

Guanine/thymine mispair binding is important because G/T mispairs are among the most frequent spontaneous DNA lesions, and their recognition is a critical checkpoint for maintaining genome stability. Proteins that bind G/T mispairs initiate repair pathways that prevent mutations, and defects in these proteins are associated with cancer and other genome instability disorders. Studying this molecular function helps researchers understand how cells detect and respond to DNA damage, and it provides a basis for developing therapeutic strategies that target DNA repair in cancer.

The following genes encode proteins that have been reported to bind G/T mispairs or are functionally associated with this activity, based on published literature and GO annotations.

The activity of guanine/thymine mispair binding is regulated at multiple levels, including post-translational modifications such as phosphorylation and ubiquitination, which can alter protein localization or affinity for damaged DNA. Additionally, the expression levels of genes encoding G/T binding proteins are controlled by transcription factors and microRNAs in response to DNA damage. The DNA damage response kinases ATM and ATR can phosphorylate downstream targets to modulate repair activity. Chromatin remodeling also plays a role by controlling access to G/T mispairs within nucleosomes.

Defects in proteins that bind G/T mispairs, such as MSH2 and MSH6, are associated with Lynch syndrome and other hereditary cancers. Loss of G/T mispair recognition leads to microsatellite instability and a mutator phenotype. Tumors with mismatch repair deficiency often show resistance to certain chemotherapies but may respond to immune checkpoint inhibitors. Studying G/T mispair binding can inform cancer diagnosis and treatment.

Mismatch repair proteins that recognize G/T mispairs have been implicated in triplet repeat expansion diseases, such as Huntington's disease and fragile X syndrome. The binding of these proteins to mispaired DNA during replication or repair can promote repeat instability. Understanding the molecular details of G/T mispair binding may suggest therapeutic strategies for these disorders.

Accumulation of DNA damage, including G/T mispairs, is a hallmark of aging. Reduced efficiency of G/T mispair binding and repair can contribute to age-related functional decline. Research on this molecular function may provide insights into interventions that promote healthy aging.

EMSA is a classic method to detect protein-DNA binding, including G/T mispair binding. A labeled DNA probe containing a G/T mispair is incubated with cell extracts or purified protein, and the formation of protein-DNA complexes is visualized on a gel. This method can be used to compare binding affinity between wild-type and mutant proteins.

SPR measures real-time binding kinetics between a protein and immobilized DNA containing a G/T mispair. It provides quantitative data on association and dissociation rates, which are useful for comparing mutants. SPR can be used to screen for small molecule inhibitors of G/T mispair binding.

Structural techniques can reveal the atomic details of how proteins recognize G/T mispairs. Crystal structures of DNA repair proteins bound to mismatched DNA have provided insights into specificity. Cryo-EM is increasingly used for large complexes.

CRISPR knockout and knock-in models allow researchers to test the role of specific genes in G/T mispair binding. Library screening can identify novel genes required for this function. These approaches are powerful for linking genotype to molecular phenotype.

Researchers studying guanine/thymine mispair binding-related genes often need to determine whether a candidate gene is causally involved in DNA repair, cancer predisposition, or genome stability. EDITGENE provides a comprehensive suite of CRISPR-based cell models and screening services to accelerate this research.

Guanine/thymine mispair binding (GO:0032137) is a fundamental molecular function that underlies DNA mismatch recognition and repair. It is essential for maintaining genome stability, and its dysregulation is linked to cancer and other diseases. Researchers can study this function using a variety of biochemical, structural, and CRISPR-based methods. EDITGENE offers a comprehensive suite of services to support these studies, from knockout cell lines to CRISPR library screening.