Novel Form of JARID2 is Required to Regulate Differentiation in Keratinocytes.

Polycomb repressive complex-2 (PRC2) is a group of proteins that play important role during development and in cell differentiation. PRC2 is a histone-modifying complex that catalyses methylation of lysine 27 of histone H3 (H3K27me3) at differentiation genes leading to their transcriptional repression. JARID2 is a co-factor of PRC2 and is important for targeting PRC2 to chromatin as well as modulating its activity. Here, we show that in many human cells, including human epidermal keratinocytes, JARID2 predominantly exists as a novel low molecular weight form, which lacks the N-terminal PRC2-interacting domain (?N-JARID2). We show that ?N-JARID2 is a cleaved product of full-length JARID2 spanning the C-terminal conserved region consisting of jumonji domains. JARID2 knockout in keratinocytes results in up-regulation of cell cycle genes and repression of many epidermal differentiation genes. Surprisingly, repression of epidermal differentiation genes in JARID2-null keratinocytes can be relieved by expression of ?N-JARID2 suggesting that this form promotes activation of these genes and has opposing function to that of PRC2 in regulation of differentiation. We propose that a switch from expression of full-length JARID2 to ?N-JARID2 is important for the up-regulation of genes during differentiation. Overall design: RNA-seq analysis of Wildtype and JARID2-null keratinocytes (HaCaTs) on day 0 and day 3 of calcium induced differentiation.

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Al-Raawi D, Jones R, Wijesinghe S, Halsall J, Petric M, Roberts S, Hotchin NA, Kanhere A