The role of the transcript elongation factors FACT and HUB1 in leaf growth and the induction of flowering

Abstract

In the cell nucleus, the packaging of the DNA into chromatin represses transcription by restricting the access of transcriptional regulators to their binding sites and inhibiting the progression of RNA polymerases during transcript elongation. To efficiently transcribe genes in the context of chromatin, eukaryotes have a variety of transcript elongation factors promoting transcription in vivo. The facilitates chromatin transcription (FACT) complex consisting of the SSRP1 and SPT16 proteins, is a histone chaperone that assists transcription by destabilising nucleosomes in the path of RNA polymerases. In a recent study, we report that Arabidopsis FACT is critically involved in different aspects of development including leaf growth and the transition to flowering. Moreover, FACT was found to interact genetically with HUB1 that mono-ubiquitinates histone H2B. Depending on the underlying process that is regulated by the two complexes, there appear to be different levels of interaction.

Figure 1

Rosette leaf size and shape of mutants in FACT, Elongator and HUB1 chromatin-related factors. The spt16-1 and ssrp1-2 mutants are in Col background and the elo3-1 and hub1-1 mutants are in Ler background. Twenty-four-day-old plants were grown on rockwool watered with Hyponex solution in growth chamber using conditions of 100 µmol/m⁻²sec⁻¹ cool white light intensity, 16 hrs light, 21°c and 60% relative humidity.