The nuclear exosome subunit, HEN2, acts independently from the core exosome to stimulate cold induced transcription at a subset of genes

Regulation of gene expression is at the frontier of plant response to various external stimuli including stress. RNA polymerase-based transcription and post-transcriptional degradation of RNA play vital roles in this regulation. Here, we show that Hua Enhancer 2 (Hen2), a component of nuclear exosome targeting (NEXT) complex, also influences RNAPII transcription elongation in cold. Our results demonstrate that hen2 is cold sensitive and undergoes significant transcriptional changes when exposed to cold. We found an accumulation of 5' fragments from a subset of genes (including C-repeat binding factors 1-3 (CBF1-3)) does not carry over to their 3' ends. This accumulation was not observed in other NEXT complex members or sop2 (an exosome mutant), highlighting HEN2's unique role. We further used RNAPII associated nascent RNA to confirm the 5' end accumulation is a result of lower transcription of these genes in hen2 mutant. Taken together our data points to a unique role of HEN2 in maintaining RNAPII transcription dynamics especially highlighted under cold stress.