Biology subjects

Schalch, T.

Publications and source records attributed to Schalch, T..

3 recordsLinked to original sources

bioRxiv2026

The HMD domain of the PAF complex primes Rad6-Bre1 E3 ligase complexes for H2B ubiquitination

Mono-ubiquitination of histone H2B (H2Bub) is deposited by Bre1-type E3 ubiquitin ligase complexes during transcription elongation and is critical for chromatin organization, DNA repair, and transcription regulation. In S. pombe, this activity is carried out by HULC, a complex of the Bre1 homologs Brl1 and Brl2 with Rhp6 and Shf1. While H2Bub deposition depends on recruitment of HULC to RNA Pol II by the Paf1 complex (PAF1C), the molecular basis for how PAF1C activates HULC has remained unclear. Using AlphaFold modelling, biochemical reconstitution, and functional assays, we define the architecture of HULC as a flexible 1:1:1:1 assembly in which Shf1 stabilizes an elongated coiled-coil hairpin that brings the RING and Rad6-binding domains into proximity. However, for full stimulation of HULC activity, we find that the HMD domain of the PAF1C subunit Prf1 stimulates ubiquitin transfer through a RING-binding region (RBR) that repositions the RING domains adjacent to Rhp6 in a catalytically competent configuration. These findings reveal an activation mechanism in which transcription-associated Prf1 primes HULC for ubiquitin transfer through the Prf1RBR, revealing a critical regulatory interface for H2B ubiquitination.

molecular biology↗

bioRxiv2022

Structural insights into the regulation of acetylation-dependent genome condensation

Histone modifications are deposited by chromatin modifying enzymes and read out by proteins that recognize the modified state. BRD4-NUT is an oncogenic fusion protein of the acetyl lysine reader BRD4 that binds to the acetylase p300 and enables formation of long-range intra- and interchromosomal interactions. We here examine how acetylation reading and writing enable formation of such interactions. We show that NUT contains an acidic transcriptional activation domain that binds to the TAZ2 domain of p300. We use NMR to investigate the structure of the complex and found that the TAZ2 domain has an autoinhibitory role for p300. NUT-TAZ2 interaction or mutations found in cancer that interfere with autoinhibition by TAZ2 allosterically activate p300. p300 activation results in a self-organizing, acetylation-dependent feed-forward reaction that enables long-range interactions by bromodomain multivalent acetyl-lysine binding. We discuss the implications for chromatin organisation, gene regulation and dysregulation in disease.

biochemistry↗

bioRxiv2020

SUV39 SET domains mediate crosstalk of heterochromatic histone marks

The SUV39 class of methyltransferase enzymes deposits histone H3 lysine 9 di- and trimethylation (H3K9me2/3), the hallmark of constitutive heterochromatin. How these enzymes are regulated to mark specific genomic regions as heterochromatic is poorly understood. Clr4 is the sole H3K9me2/3 methyltransferase in the fission yeast S. pombe and recent evidence suggests that ubiquitination of lysine 14 on histone H3 (H3K14ub) plays a key role in H3K9 methylation. However, the molecular mechanism of this regulation and its role in heterochromatin formation remains to be determined. Our structure-function approach shows that the H3K14ub substrate binds specifically and tightly to the catalytic domain of Clr4, and thereby stimulates the enzyme by over 250-fold. Mutations that disrupt this mechanism lead to a loss of H3K9me2/3 and abolish heterochromatin silencing similar to clr4 deletion. Comparison with mammalian SET domain proteins suggests that the Clr4 SET domain harbours a conserved sensor for H3K14ub, which mediates licensing of heterochromatin formation.

molecular biology↗