#protein-DNA interactions

Transcript analysis

In a DNase I footprinting assay, a missing band indicates:

DNase I footprinting identifies precise binding sites of DNA-binding proteins. End-labeled DNA fragment is partially digested with DNase I, a non-specific endonuclease introducing single-strand nicks at random phosphodiester bonds, generating ladder when resolved on denaturing gel. Pre-incubation with DNA-binding protein protects phosphodiester backbone within contact region from cleavage, preventing production of corresponding fragments. Hence protected region appears as gap, or missing bands, footprint against background ladder. Position of gap defines recognition site, while flanking cleava

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details

DNA-Protein Interaction analysis

In DNase I footprinting, the absence of bands indicates:

In DNase I footprinting, limited digestion of labeled DNA normally generates ladder representing cleavage at every accessible phosphodiester bond. After denaturing gel electrophoresis, band pattern reflects random cuts. When DNA-binding protein occupies specific sequence, it sterically shields underlying backbone, preventing DNase I access and cleavage at those positions. Hence corresponding bands disappear, leaving clear window termed footprint. Location and length of absent bands map binding motif coordinates. This absence indicates protected protein-bound region, distinguishing sequence-spe

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details

DNA-Protein Interaction analysis

EMSA is used to study:

Electrophoretic Mobility Shift Assay is a classical in vitro method for analyzing DNA-protein interaction. A radiolabeled or fluorescent DNA probe containing putative binding site is incubated with purified protein or nuclear extract, then resolved on non-denaturing polyacrylamide gel. Free DNA migrates rapidly due to high negative charge. DNA bound to protein gains increased mass, reduced charge-to-mass ratio and conformational change, causing retarded mobility. Appearance of shifted band demonstrates specific physical association. Competitor DNA tests specificity, while titration estimates a

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details

Gene Tar getting

Which genome editing platform uses protein-DNA interactions to determine specificity?

Genome editing specificity can derive from protein-DNA contacts versus RNA-DNA base pairing. CRISPR Cas9 relies on guide RNA pairing and PAM. RNA interference uses small RNA-mRNA complementarity. Zinc finger nucleases use engineered arrays of Cys2His2 zinc finger domains, each recognizing three nucleotides via alpha helix contacting major groove. Tandem fingers create specific protein-DNA interface fused to FokI nuclease. Thus ZFN specificity is entirely determined by protein side chain interactions with DNA bases, requiring modular assembly and selection to achieve desired target without RNA

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details