Introduction:
Protein binding regions of DNA refer to specific regions of DNA where proteins bind in order to regulate gene expression, DNA replication, and other cellular processes. Identifying these protein binding regions is crucial for understanding gene regulation and the underlying mechanisms of various cellular processes.

Foot Printing Technique:
The technique used to identify protein binding regions of DNA is called "foot printing." It involves the use of a DNAse enzyme to determine the regions of DNA that are protected by protein binding. This technique is also known as DNase I footprinting.

Procedure:
1. Isolation of DNA-Protein Complex: First, the DNA-protein complex is isolated from cells or tissues. This can be done by treating the cells with a crosslinking agent to fix the DNA-protein interactions.

2. DNase I Digestion: The isolated DNA-protein complex is then treated with DNase I, an enzyme that cleaves DNA at specific sites. However, the DNA regions protected by protein binding remain undigested.

3. Stopping the Digestion: The DNase I digestion is stopped by adding an appropriate stop solution, which inhibits further cleavage of DNA.

4. DNA Fragmentation and Analysis: The DNA is then extracted and fragmented using a restriction enzyme or by denaturation and re-annealing. The fragments are separated by gel electrophoresis, resulting in a ladder-like pattern of DNA fragments.

5. Visualization and Interpretation: The gel is stained with a DNA-specific dye, such as ethidium bromide, and visualized under UV light. The protected regions of DNA, where proteins were bound, appear as "footprints" or gaps in the DNA ladder pattern.

Advantages of Foot Printing:
- Foot printing is a sensitive and specific technique for identifying protein binding regions of DNA.
- It provides information about the precise location and sequence specificity of protein-DNA interactions.
- Foot printing can be used to study the binding of various proteins, including transcription factors, nucleosomes, and DNA repair proteins.

In conclusion, foot printing is a technique used to identify protein binding regions of DNA by treating the DNA-protein complex with DNase I and analyzing the resulting DNA fragments. This technique provides valuable insights into the mechanisms of gene regulation and other cellular processes.