Question

The electrophoretic mobility shift assay (EMSA) experiment demonstrated the very powerful technique for determining protein-DNA interactions. For this purpose the EMSA can be used qualitatively to

a. identify unknown DNA molecules.

b. detect DNA - RNA interactions.

c. identify specific transcriptional or co-transcriptional factors.

d. identify isoenzymes.

Answer 1

Electrophoretic mobility shift assay (EMSA) is a simple technique to identify DNA-protein or RNA-protein interactions. Molecules of different size, shape or charge will have different electrophoretic mobility in a non-denaturing gel. EMSA is based on the ability of a DNA-protein complex to migrate slowly in electrophoresis gel due to large size, creating a gel shift. Free nucleic acids will run faster on a gel. EMSA involves labeling the DNA probe, DNA–protein binding reaction, and analysis on a native polyacrylamide gel.

Transcription factors are proteins that bind to DNA-regulatory sequences (enhancers and silencers), present in 5’ -upstream region of target genes. They enhance transcription. Co-transcriptional factors are proteins that can bind to RNA. Pre-mRNA is converted to mature mRNA after capping, splicing, and poly adenylation. Several proteins are associated with RNA during co-transcriptional processing. These interactions can be detected by EMSA.

Right option is c. identity specific transcriptional or co-transcriptional factors.