An open or closed case for HMGA

Senescence turns a chromatin-activating protein towards the dark side. Upon senescence induction, high mobility group A (HMGA) protein helps to make silent heterochromatin, report Masashi Narita, Scott Lowe, and colleagues (Cold Spring Harbor Laboratory, NY).

HMGA proteins promote open and active chromatin, are highly expressed in the early embryo, and can promote tumorigenesis. But the new results now show that HMGA is also found in senescent cells, which—in stark contrast to embryonic or tumor cells—no longer respond to mitogenic stimuli.

Senescent cells often form dense nuclear chromatin blobs called senescence-associated heterochromatic foci (SAHF), which the Lowe lab first described three years ago. While working to determine the chromatin components and epigenetic modifications that characterize SAHFs, they found that HMGA was upregulated in senescent cells. Its previously diffuse nuclear distribution in normal cells...