Transcript Elongation Factor TFIIS Is Involved in Arabidopsis Seed Dormancy Marion Grasser 1 , Caroline M. Kane 2 , Thomas Merkle 3 , Michael Melzer 4 , Jeppe Emmersen 5 and Klaus D. Grasser 1 ⁎ 1 Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark 2 Molecular and Cell Biology, University of California, 408 Barker Hall, Berkeley, CA 94720-3202, USA 3 Genome Research, Faculty of Biology, University of Bielefeld, Universitätsstr. 25, D-33594 Bielefeld, Germany 4 Leibniz Institute of Plant Genetics and Crop Plant Research, Corrensstr. 3, D-06466 Gatersleben, Germany 5 Department of Health Science and Technology, Aalborg University, Fredrik Bajersvej 7, DK-9220 Aalborg, Denmark Received 16 October 2008; received in revised form 13 December 2008; accepted 22 December 2008 Available online 3 January 2009 Transcript elongation factor TFIIS promotes efficient transcription by RNA polymerase II, since it assists in bypassing blocks during mRNA synthesis. While yeast cells lacking TFIIS are viable, inactivation of mouse TFIIS causes embryonic lethality. Here, we have identified a protein encoded in the Arabidopsis genome that displays a marked sequence similarity to TFIIS of other organisms, primarily within domains II and III in the C-terminal part of the protein. TFIIS is widely expressed in Arabidopsis, and a green fluorescent protein–TFIIS fusion protein localises specifically to the cell nucleus. When expressed in yeast cells lacking the endogenous TFIIS, Arabidopsis TFIIS partially complements the sensitivity of mutant cells to the nucleotide analog 6-azauridine, which is a typical characteristic of transcript elongation factors. We have characterised Arabidopsis lines harbouring T-DNA insertions in the coding sequence of TFIIS. Plants homozygous for T-DNA insertions are viable, and genomewide transcript profiling revealed that compared to control plants, a relatively small number of genes are differentially expressed in mutant plants. TFIIS -/- plants display essentially normal development, but they flower slightly earlier than control plants and show clearly reduced seed dormancy. Plants with RNAi-mediated knockdown of TFIIS expression also are affected in seed dormancy. Therefore, TFIIS plays a critical role in Arabidopsis seed development. © 2008 Elsevier Ltd. All rights reserved. Edited by J. Karn Keywords: transcript elongation; RNA polymerase II; transcriptome; yeast complementation; nuclear localisation Introduction Transcription by RNA polymerase II (RNAPII) proceeds through multiple stages, including promoter recruitment, initiation, elongation, and termination. The vast majority of studies investigating the regula- tion of eukaryotic transcription have focused on the early stages of the transcription cycle (i.e., preinitiation and initiation). In the past few years, it has become apparent that mRNA synthesis is a dynamic and highly regulated step in gene expression that requires the concerted action of a variety of transcript elonga- tion factors. 1–3 One of the factors regulating transcript elongation is TFIIS, which was identified early as an activity that facilitated transcript elongation in vitro. 4 The ∼ 35-kDa TFIIS of yeast and mammals is a three- domain protein. Domain I has the least sequence conservation and comprises the N-terminal part of the protein that forms a four-helix bundle and is dis- pensable for transcription stimulation in vitro. The central domain II contains a well-defined three-helix bundle and (together with the linker region between *Corresponding author. E-mail address: kdg@bio.aau.dk. Abbreviations used: RNAPII, RNA polymerase II; 6-AU, 6-azauridine; daf, days after flowering; rtPCR, reverse-transcribed polymerase chain reaction; GFP, green fluorescent protein; GPD, glyceraldehyde-3-phosphate dehydrogenase; GO, gene ontology. doi:10.1016/j.jmb.2008.12.066 J. Mol. Biol. (2009) 386, 598–611 Available online at www.sciencedirect.com 0022-2836/$ - see front matter © 2008 Elsevier Ltd. All rights reserved.