Take our Survey

Reference: Hou Z, et al. (2009) Phylogenetic conservation and homology modeling help reveal a novel domain within the budding yeast heterochromatin protein Sir1. Mol Cell Biol 29(3):687-702

Reference Help

Abstract


The yeast Sir1 protein's ability to bind and silence the cryptic mating-type locus HMRa requires a protein-protein interaction between Sir1 and the Origin Recognition Complex (ORC). A domain within the C-terminal half of Sir1, the Sir1OIR (ORC Interaction Region) and the conserved Bromo-Adjacent Homology (BAH) domain within Orc1, the largest subunit of ORC, mediate this interaction. The structure of the Sir1OIR-Orc1BAH complex is known. Sir1OIR and Orc1BAH interacted with a high affinity in vitro, but the Sir1OIR did not inhibit Sir1-dependent silencing when overproduced in vivo, suggesting other regions of Sir1 helped it bind HMRa. Comparisons of diverged Sir1 proteins revealed two highly conserved regions, N1 and N2, within Sir1's poorly characterized N-terminal half. An N-terminal portion of Sir1 (residues 27-149; Sir1(27-149)) is similar in sequence to the Sir1OIR; homology modeling predicted a structure for Sir1(27-149) in which N1 formed a sub-module similar to the known Orc1BAH-interacting surface on Sir1. Consistent with these findings, 2-hybrid assays indicated that the Sir1 N-terminus could interact with BAH-domains. Amino acid substitutions within or near N1 or N2 reduced full-length Sir1's ability to bind and silence HMRa and to interact with Orc1BAH in a 2-hybrid assay. Purified recombinant Sir1 formed a large protease-resistant structure within which the Sir1OIR domain was protected, and Orc1BAH bound Sir1OIR more efficiently than full-length Sir1 in vitro. Thus the Sir1 N-terminus exhibited both positive and negative roles in the formation of a Sir1-ORC silencing complex. This functional duality might contribute to Sir1's selectivity for silencer-bound ORCs in vivo.

Reference Type
Journal Article
Authors
Hou Z, Danzer JR, Mendoza L, Bose ME, Muller U, Williams B, Fox CA
Primary Lit For
Additional Lit For
Review For

Interaction Annotations


Increase the total number of rows showing on this page by using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small "i" buttons located within a cell for an annotation to view further details about experiment type and any other genes involved in the interaction.

Interactor Interactor Type Assay Annotation Action Modification Phenotype Source Reference

Gene Ontology Annotations


Increase the total number of rows showing on this page using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table.

Gene Gene Ontology Term Qualifier Aspect Method Evidence Source Assigned On Annotation Extension Reference

Phenotype Annotations


Increase the total number of rows showing on this page using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small "i" buttons located within a cell for an annotation to view further details.

Gene Phenotype Experiment Type Mutant Information Strain Background Chemical Details Reference

Regulation Annotations


Increase the total number of rows displayed on this page using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; to filter the table by a specific experiment type, type a keyword into the Filter box (for example, “microarray”); download this table as a .txt file using the Download button or click Analyze to further view and analyze the list of target genes using GO Term Finder, GO Slim Mapper, SPELL, or YeastMine.

Regulator Target Experiment Assay Construct Conditions Strain Background Reference