Showing papers by "Andreas G. Ladurner published in 2008"

The FACT Spt16 “peptidase” domain is a histone H3–H4 binding module

Abstract: The FACT complex is a conserved cofactor for RNA polymerase II elongation through nucleosomes. FACT bears histone chaperone activity and contributes to chromatin integrity. However, the molecular mechanisms behind FACT function remain elusive. Here we report biochemical, structural, and mutational analyses that identify the peptidase homology domain of the Schizosaccharomyces pombe FACT large subunit Spt16 (Spt16-N) as a binding module for histones H3 and H4. The 2.1-A crystal structure of Spt16-N reveals an aminopeptidase P fold whose enzymatic activity has been lost. Instead, the highly conserved fold directly binds histones H3-H4 through a tight interaction with their globular core domains, as well as with their N-terminal tails. Mutations within a conserved surface pocket in Spt16-N or posttranslational modification of the histone H4 tail reduce interaction in vitro, whereas the globular domains of H3-H4 and the H3 tail bind distinct Spt16-N surfaces. Our analysis suggests that the N-terminal domain of Spt16 may add to the known H2A-H2B chaperone activity of FACT by including a H3-H4 tail and H3-H4 core binding function mediated by the N terminus of Spt16. We suggest that these interactions may aid FACT-mediated nucleosome reorganization events.

Repression of RNA polymerase II transcription by a Drosophila oligopeptide.

Abstract: Background: Germline progenitors resist signals that promote differentiation into somatic cells. This occurs through the transient repression in primordial germ cells of RNA polymerase II, specifically by disrupting Ser2 phosphorylation on its Cterminal domain. Methodology/Principal Findings: Here we show that contrary to expectation the Drosophila polar granule component (pgc) gene functions as a protein rather than a non-coding RNA. Surprisingly, pgc encodes a 71-residue, dimeric, alphahelical oligopeptide repressor. In vivo data show that Pgc ablates Ser2 phosphorylation of the RNA polymerase II C-terminal domain and completely suppresses early zygotic transcription in the soma. Conclusions/Significance: We thus identify pgc as a novel oligopeptide that readily inhibits gene expression. Germ cell repression of transcription in Drosophila is thus catalyzed by a small inhibitor protein.

PARP: a transferase by any other name.

Abstract: A recent report shows that several 'poly-ADP-ribose-polymerases' may function exclusively as a family of endogenous mono-ADP-ribosyltransferases, providing a new, molecularly less complex and broadened cellular role for this elusive post-translational modification.