Regulation by p53
p53 functions primarily as a transcription factor, a protein that regulates the activity of other genes. Part of the reason that p53 can do so many things is that it controls the expression of many other genes.
A single p53 molecule is not really functional. To bind to DNA and activate other genes, it has to form a complex by joining with three other p53 molecules. The domain (protein region) where the four p53 molecules bind to one another is shown in yellow.
A close-up of the colored blobs from the previous image with the same series of colored rectangles of different lengths labeling various parts of the image. The red blob is labeled Transactivation, the green blob is labeled DNA binding, and the yellow blob is labeled Complexing.