During backtracking, the 3′-end of the nascent RNA is displaced from the polymerase active core. Diverse circumstances may halt and cause subsequent backtracking of RNAPII.
In eukaryotes, RNA polymerase II (RNAPII) is responsible for transcription of most mRNAs. However, recent results have shown that elongation is also precisely regulated ( 1–3). Traditionally, it was considered that transcription is regulated at the initiation step. Transcriptional regulation plays a key role in stress responses.
Plants have sophisticated mechanisms for the adaptation to external factors and for balancing their development and stress responses accordingly. TFIIS accumulation during heat occurs in evolutionary distant species, including the unicellular alga Chlamydomonas reinhardtii, dicot Brassica napus and monocot Hordeum vulgare, suggesting that the vital role of TFIIS in stress adaptation of plants is conserved.Įnvironmental changes continuously affect growth and reproduction of organisms. Contrary to expectations of being constantly present to support transcription, we show that TFIIS is dynamically regulated. Transcriptome changes indirectly cause proteotoxic stress and deterioration of cellular pathways, including photosynthesis, which finally leads to lethality. By employing a transcriptome analysis, we unravel that the absence of TFIIS makes transcriptional reprogramming sluggish, and affects expression and alternative splicing pattern of hundreds of heat-regulated transcripts. TFIIS activity is required for thermal adaptation throughout the whole life cycle of plants, ensuring both survival and reproductive success. Here, we show that, although TFIIS seems unnecessary under optimal conditions in Arabidopsis, its absence renders plants supersensitive to heat tfIIs mutants die even when exposed to sublethal high temperature. However, little is known about TFIIS regulation or its roles during stress responses. Elongation factor TFIIS (transcription factor IIS) is structurally and biochemically probably the best characterized elongation cofactor of RNA polymerase II.
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