The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The core pluripotency factors (Oct4, Sox2, and Nanog), the Myc network, and the chromatin-modifying complexes such as PRC2 ensure the pluripotency and self-renewal of ES cells (ESC). How these factors coordinate with one another remains poorly understood. We report that Utf1, a target of Oct4 and Sox2, is a new bivalent chromatin component that buffers poised states of bivalent genes. By limiting PRC2 loading and Histone 3 lysine-27 trimethylation, Utf1 sets proper activation thresholds for bivalent genes. It also promotes nuclear tagging of mRNAs transcribed from insufficiently silenced bivalent genes for cytoplasmic degradation through mRNA de-capping. Whereas these opposing functions of Utf1 allow proper execution of ESC pluripotency, the mRNA pruning function also ensures rapid cell proliferation by blocking the Myc-Arf feedback regulation. Thus, Utf1 is an important regulator that couples the core pluripotency factors with Myc and PRC2 networks to promote proliferation and pluripotency execution of ESCs.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.

The densities of RNA-seq reads (in reads per kilo-bases per million reads, RPKM) were normalized to the library size and the number of sites in 20bp sliding windows along the genome.