3D1B

Tetragonal crystal structure of Tas3 C-terminal alpha motif

Summary for 3D1B

• Entry DOI: 10.2210/pdb3d1b/pdb
• Related: 3D1D
• Descriptor: RNA-induced transcriptional silencing complex protein tas3 (2 entities in total)
• Functional Keywords: all alpha motif, rits complex, immunoglobulin fold, cell cycle, chromosome partition, nucleus, rna-mediated gene silencing, nuclear protein
• Biological source: Schizosaccharomyces pombe (Fission yeast)
• Cellular location: Nucleus: O94687
• Total number of polymer chains: 3
• Total formula weight: 41822.81

Authors

Li, H.,Patel, D.J. (deposition date: 2008-05-05, release date: 2009-04-21, Last modification date: 2024-02-21)

Primary citation

Li, H.,Motamedi, M.R.,Yip, C.K.,Wang, Z.,Walz, T.,Patel, D.J.,Moazed, D.
An alpha motif at Tas3 C terminus mediates RITS cis spreading and promotes heterochromatic gene silencing.
Mol.Cell, 34:155-167, 2009

PubMed Abstract: RNA interference (RNAi) plays a pivotal role in the formation of heterochromatin at the fission yeast centromeres. The RNA-induced transcriptional silencing (RITS) complex, composed of heterochromatic small interfering RNAs (siRNAs), the siRNA-binding protein Ago1, the chromodomain protein Chp1, and the Ago1/Chp1-interacting protein Tas3, provides a physical tether between the RNAi and heterochromatin assembly pathways. Here, we report the structural and functional characterization of a C-terminal Tas3 alpha-helical motif (TAM), which self-associates into a helical polymer and is required for cis spreading of RITS in centromeric DNA regions. Site-directed mutations of key residues within the hydrophobic monomer-monomer interface disrupt Tas3-TAM polymeric self-association in vitro and result in loss of gene silencing, spreading of RITS, and a dramatic reduction in centromeric siRNAs in vivo. These results demonstrate that, in addition to the chromodomain of Chp1 and siRNA-loaded Ago1, Tas3 self-association is required for RITS spreading and efficient heterochromatic gene silencing at centromeric repeat regions.

PubMed: 19394293
DOI: 10.1016/j.molcel.2009.02.032

Experimental method

X-RAY DIFFRACTION (1.7 Å)