Regulation of Mammalian Cell Growth and Survival By an RNA Polymerase II-Pausing Factor (Gene expression)

Many mammalian genes are occupied by paused RNA polymerase II (pol II) at promoter-proximal regions on both sides of transcription start sites (TSSs). However, the consequences of pol II pausing on gene expression and cell biology are not fully understood. Here we report that genetic ablation of the b subunit of mouse negative elongation factor (Nelf-b), a key pol II-pausing factor, results in slower progression at multiple cell cycle stages and increased apoptosis. Consistently, a whole-genome analysis indicates that growth and cell death-related genes are highly enriched among the direct target genes of Nelf-b. In particular, Nelf-b deletion increases pol II density in the promoter-distal region of stress response genes and their overall expression levels in the absence of any external stress signals. In addition, our work also reveals a previously unappreciated role of Nelf-b role in curbing TSS-upstream transcription of many mammalian genes. We suggest that Nelf-mediated pol II pausing balances the cellular needs for growth/survival and stress response by preventing excessive basal transcription of stress-induced genes. Immortalized mouse embryonic fibroblasts derived from a Nelf-b flox/- embryo were infected with control or Cre-epxressing retrovirus. Gene expression profile of control and knockout MEF at 7 days after virus infection were compared by using Illumina's mouse whole-genome gene expression BeadChIPs. There are two replicates for both control and knockout MEF samples.