PDBsum entry 3d1b

Nuclear protein

PDB id: 3d1b

Contents

Protein chains

111 a.a.

Waters ×394

PDB id:

3d1b

Name:

Nuclear protein

Title:

Tetragonal crystal structure of tas3 c-terminal alpha motif

Structure:

RNA-induced transcriptional silencing complex protein tas3. Chain: a, b, c. Fragment: unp residues 426-545. Synonym: rits protein tas3. Engineered: yes

Source:

Schizosaccharomyces pombe. Fission yeast. Organism_taxid: 4896. Gene: tas3, spbc83.03c. Expressed in: escherichia coli.

Resolution:

1.70Å R-factor: 0.207 R-free: 0.237

Authors:

H.Li,D.J.Patel

Key ref:

H.Li et al. (2009). An alpha motif at Tas3 C terminus mediates RITS cis spreading and promotes heterochromatic gene silencing. Mol Cell, 34, 155-167. PubMed id: 19394293

Date:

05-May-08 Release date: 21-Apr-09

Protein chains

O94687  (TAS3_SCHPO) -  RNA-induced transcriptional silencing complex protein tas3 from Schizosaccharomyces pombe (strain 972 / ATCC 24843)

Seq: 549 a.a.

Struc: 111 a.a.

Enzyme reactions

• Enzyme class: E.C.?

Mol Cell 34:155-167 (2009)

PubMed id: 19394293

An alpha motif at Tas3 C terminus mediates RITS cis spreading and promotes heterochromatic gene silencing.

H.Li, M.R.Motamedi, C.K.Yip, Z.Wang, T.Walz, D.J.Patel, D.Moazed.

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.