05-P002 Developmental functions of the PcG gene Yy1 in the mouse

During healing of a skin wound, cells that are normally dormant must turn on hundreds of genes in order to proliferate, migrate, and repair the defect. The Polycomb family of proteins epigenetically silence target genes and so downregulation of their expression is a potential mechanism for unsilencing repair genes. Quantitative RT-PCR, western blotting, and immunostaining of invitro epithelial scratch wounds and invivo mouse skin wounds reveal that the Polycombs Eed and Ezh2 are downregulated during repair. How is their expression regulated? JNK signalling, which is well known to be activated during wound healing, is reported to decrease polycomb expression in other settings. We have manipulated this pathway during invitro and invivo repair to establish whether wound-triggered JNK activation is responsible for Polycomb downregulation. Blocking JNK signalling resulted in an increase of Eed protein levels, whilst the converse, enhancement of JNK signalling, led to a more marked downregulation of Eed during repair. Chromatin immunoprecipitation (ChIP) experiments, to reveal direct interaction between components of the AP-1 complex and eed promoter, showed that there is increased binding of Fos and Jun to the eed promoter during the tissue repair process, both in the invitro assay and during the invivo wound response.