Heterochromatingets dynamic

The sleeping giant of the cell, heterochromatin, is really a bustling complex whose components turn over rapidly, say two groups led by Richard Festenstein (Imperial College, London) and Thierry Cheutin and Tom Misteli (National Cancer Institute [NCI], Bethesda, MD).

Both groups used fluorescence recovery after photobleaching (FRAP) to track the behavior of heterochromatin protein 1 (HP1). HP1 was not static but moving around, as Misteli puts it, in the “same sort of range” as transcription factors.

Although both groups found that HP1 was dynamic, Festenstein's mobility values were lower than those found by Misteli. Part of the difference may lie in varying bleaching and microscopy methods, but both researchers suggest the importance of the different cell types used. Festenstein looked in primary T cells—a resting cell type—and when he stimulated the T cell receptor to activate...