Ingenious mechanism to ensure robust Polycomb silencing

Press Release

Division of Neurogenetics

Mbf1 ensures Polycomb silencing by protecting E(z) mRNA from degradation by Pacman

Kenichi Nishioka, Xian-Feng Wang, Hitomi Miyazaki, Hidenobu Soejima, Susumu Hirose

Development 2018 145:dev162461 DOI:10.1242/dev.162461

Pressrelease (In Japanese only)

Under stress conditions, the coactivator Multiprotein-bridging factor 1 (Mbf1) translocates from the cytoplasm into the nucleus to induce stress-response genes. However, its role in the cytoplasm, where it is mainly located, has remained elusive. Here, we show that Drosophila Mbf1 associates with E(z) mRNA and protects it from degradation by the exoribonuclease Pacman, thereby ensuring Polycomb silencing. This mechanism would also allow flexibility in Polycomb silencing, as Mbf1 protein expression declines upon differentiation.

In addition to E(z) mRNA, Mbf1 binds to mRNAs of various stress-response genes. Therefore, Mbf1 appears to contribute to various types of stress defense as both a nuclear coactivator and as a cytoplasmic mRNA-stabilizing protein. It is intriguing that Mbf1 contributes to the same biological function through different subcellular localisation.


Mbf1 binds to E(z) mRNA and protects it from degradation by Pacman. Polycomb silencing represses expression of the pacman gene. Therefore, Mbf1 ensures robust Polycomb silencing.

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