Effect of UV irradiation on Sulfolobus acidocaldarius and involvement of the general transcription factor TFB3 in the early UV response

Abstract

Exposure to UV light can result in severe DNA damage. The alternative general transcription factor (GTF) TFB3 has been proposed to play a key role in the UV stress response in the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. Reporter gene assays confirmed that tfb3 is upregulated 90–180 min after UV treatment. In vivo tagging and immunodetection of TFB3 confirmed the induced expression at 90 min. Analysis of a tfb3 insertion mutant showed that genes encoding proteins of the Ups pili and the Ced DNA importer are no longer induced in a tfb3 insertion mutant after UV treatment, which was confirmed by aggregation assays. Thus, TFB3 plays a crucial role in the activation of these genes. Genome wide transcriptome analysis allowed a differentiation between a TFB3-dependent and a TFB3-independent early UV response. The TFB3-dependent UV response is characterized by the early induction of TFB3, followed by TFB3-dependent expression of genes involved in e.g. Ups pili formation and the Ced DNA importer. Many genes were downregulated in the tfb3 insertion mutant confirming the hypothesis that TFB3 acts as an activator of transcription. The TFB3-independent UV response includes the repression of nucleotide metabolism, replication and cell cycle progression in order to allow DNA repair.

Early Response of Sulfolobus acidocaldarius to Nutrient Limitation

“…However, in contrast to Eukaryotes most Archaea encode multiple GTFs. S. acidocaldarius encodes for one TBP ( saci_1336 ), three TFBs [TFB1 ( saci_0866 ), TFB2 ( saci_1341 ) and TFB3 ( saci_0665 )] and one TFE with α- and β- subunit ( saci_0652 and saci_1342 , respectively) (Bell and Jackson, 2000; Blombach et al, 2015; Feng et al, 2018; Schult et al, 2018). Upon nutrient depletion, transcript levels of TFB1, TFB2 , and TFEβ were elevated (Supplementary Table S2) whereas the transcription of TBP, TFB3 , and TFEα was not affected.…”

Phosphorylation of the Archaeal Holliday Junction Resolvase Hjc Inhibits Its Catalytic Activity and Facilitates DNA Repair in Sulfolobus islandicus REY15A

“…It recognizes and binds to the promoter regions of DDR and Tfb3 genes and activates or represses their expression (Sun et al, 2018). Tfb3 upregulates a subset of gene expression including mre11-herA-nurA-rad50 operon, ups , and ced gene transfer system, while represses those in DNA replication initiation, genome segregation, and cell division (Feng et al, 2018; Schult et al, 2018). However, many details of the network await investigation.…”

The cutting edge of archaeal transcription

“…TFB3, a TFB paralogue in Sulfolobus that is induced by UV-radiation and DNA damage, cannot replace the canonical TFB homologue, but rather appears to activate transcription in conjunction with canonical TFB in trans via a mechanism that is still poorly understood [41]. Recent insights into the genes under direct control of TFB3 provide now a basis for functional studies into the molecular mechanism of transcription activation by TFB3 [42,43].…”