Topic: Histones

Histone tails, which extend from tightly-wrapped DNA-histone spools, are strings of amino acids that serve as targets for chemical processes that grant access to specific genes.

Histones are proteins that package and order DNA into complexes called nucleosomes, and by facilitating the ability of the cell’s transcription machinery to access specific segments of DNA they are believed to play an important role in gene regulation.

Histone tails, long flexible proteins that protrude from the tightly wrapped DNA-histone “spools,” are the key to turning individual genes on and off. According to a hypothesis proposed by Rockefeller’s C. David Allis and his colleagues, chemical modifications to specific amino acids on histone tails act like flags to direct the docking of other proteins that open up the DNA coils and provide access to genes. Chemical modifications of histones were first identified by Rockefeller scientist Vincent G. Allfrey in the early 1960s.

The ability of histones to “interpret” the genetic code may help explain why not all inheritable traits can be traced back to mutations in the DNA sequence. The study of non-DNA encoded heritable information, including histone modifications, is known as epigenetics, and it is a fast-growing field in biology. Rockefeller scientists have shown that histone modifications play roles in embryonic development and human diseases such as cancer, mental retardation and drug addictions.