Since our interview last year with Steve Henikoff, in which we discussed his Roadmap Epigenomics R21 grant, we’ve been itching to learn all the details of his new method for studying nucleosome turnover. On May 28, our wait was finally over with the debut of the CATCH-IT (covalent attachment of tags to capture histones and identify turnover) technique in the journal Science.
Henikoff and co-workers at Fred Hutchinson Cancer Research Center showed that it’s really possible to get a focused snapshot of the chromatin landscape in cells at different times. The CATCH-IT strategy involves metabolic labeling of newly synthesized histones with the methionine surrogate azidohomoalanine. Unlike previous methods, CATCH-IT doesn’t require transgenes or antibodies.
Here’s what the researchers found using CATCH-IT in Drosophila cells:
- Nucleosomes had quicker turnover at active gene bodies, replication origins, and epigenetic regulatory elements
- Turnover was faster at DNA sites for trithorax-group protein binding than at polycomb-group binding sites. These proteins add opposing marks to histones (trithorax = activating; polycomb = repressive).
- The speedy nucleosome turnover (multiple times per cell cycle) at regulatory sites challenges models for epigenetic inheritance that depend on stable histone marks.
We can’t wait to see what other findings pop up from this powerful new technique. CATCH all the details for yourself at Science, May 2010.