PerspectiveCell Biology

When the Beginning Marks the End

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Science  19 Feb 2010:
Vol. 327, Issue 5968, pp. 966-967
DOI: 10.1126/science.1187274

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Acetylation of the amino terminus (Nt-acteylation) of a protein is one of the most common modifications, occurring in about 50% of yeast proteins and more than 80% of human proteins (1). It is catalyzed by N-terminal acetyltransferases, occurs predominantly on a nascent polypeptide chain as it is synthesized, and seems to be irreversible. So far, the biological role of Nt-acetylation has been enigmatic; only in a few cases has it been reported to affect protein functionality [for instance, nonacetylated actin is less efficient at assembling microfilaments (2)]. Controlling the activity of individual proteins cannot, however, explain the massive Nt-acetylation of bulk proteins. On page 973 in this issue, Hwang et al. (3) demonstrate that acetylation of the amino terminus of a protein can function as a degration signal (degron), revealing an entirely unexpected role of acetylation in protein turnover and possibly homeostasis.