Biology subjects

Blombach, F.

Publications and source records attributed to Blombach, F..

3 recordsLinked to original sources

bioRxiv2026

A TFIIB paralog drives cyclic transcription to orchestrate the archaeal cell cycle

Cyclic transcription is a hallmark of the cell cycle. While transcriptional waves in eukaryotes are driven by oscillations in cyclin-dependent kinase (CDK) activity, many archaea have an ordered cell cycle despite lacking CDKs. Here in exploring how cyclic transcription is achieved in Sulfolobus acidocaldarius, we show that TFB2, a paralog of eukaryotic TFIIB, is cyclically expressed, associated with the promoters of division genes (including tfb2 itself), contains a cyclin-box and is degraded as cells exit division. Furthermore, a dominant-negative TFB2 mutant interferes with division gene expression and cytokinesis. These data identify TFB2 as a central player in the circuitry orchestrating the orderly cell cycle in Sulfolobus and, despite the absence of CDKs, reveal parallels between the regulatory logic of archaeal cell division and eukaryotic mitosis.

cell biology↗

bioRxiv2023

Cbp1-Cren7 chromatinization of CRISPR arrays favours transcription from leader- over cryptic promoters

CRISPR arrays form the physical memory of CRISPR adaptive immune systems by incorporating foreign DNA as spacers that are often AT-rich and derived from viruses. As promoter elements such as the TATA-box are AT-rich, CRISPR arrays are prone to harbouring cryptic promoters. Sulfolobales harbor extremely long CRISPR arrays spanning several kilobases, a feature that is accompanied by the CRISPR-specific transcription factor Cbp1. Aberrant Cbp1 expression modulates CRISPR array transcription, but the molecular mechanisms underlying this regulation are unknown. Here, we characterise the genome-wide Cbp1 binding at nucleotide resolution and characterise the binding motifs on distinct CRISPR arrays, as well as on unexpected non-canonical binding sites associated with transposasons. Cbp1 recruits Cren7 forming together chimeric chromatin-like structures at CRISPR arrays. We dissect Cbp1 function in vitro and in vivo and show that the third HTH domain is responsible for Cren7 recruitment, and that Cbp1-Cren7 chromatinization plays a dual role in the transcription of CRISPR arrays. It suppresses spurious transcription from cryptic promoters within CRISPR arrays but enhances CRISPR RNA transcription directed from their cognate promoters in their leader region. Our results show that Cbp1-Cren7 chromatinization drives the productive expression of long CRISPR arrays.

microbiology↗

bioRxiv2020

Promoter-proximal elongation regulates transcription in archaea

Recruitment of RNA polymerase and initiation factors to the promoter is the only known mechanisms for transcription activation and repression in archaea. Whether any of the subsequent steps towards productive transcription elongation is involved in regulation is not known. We characterised how the basal transcription machinery is distributed along genes in the archaeon Sulfolobus solfataricus. We discovered a distinct early elongation phase where RNA polymerases sequentially recruit the elongation factors Spt4/5 and Elf1 to form the transcription elongation complex (TEC) before the TEC escapes into productive transcription. TEC escape is rate-limiting for transcription output during exponential growth. Oxidative stress causes changes in TEC escape that correlate with changes in the transcriptome. Our results thus establish that TEC escape contributes to the basal promoter strength and facilitates transcription regulation. Impaired TEC escape coincides with the accumulation of initiation factors at the promoter and recruitment of termination factor aCPSF1 to the early TEC. This suggests two possible mechanisms for how TEC escape limits transcription, physically blocking upstream RNA polymerases during transcription initiation and premature termination of early TECs.

molecular biology↗