BNR1/YIL159W Summary Help

Standard Name BNR1 1
Systematic Name YIL159W
Feature Type ORF, Verified
Description Formin; nucleates the formation of linear actin filaments, involved in cell processes such as budding and mitotic spindle orientation which require the formation of polarized actin cables, functionally redundant with BNI1 (2 and see Summary Paragraph)
Name Description BNi1 Related 1
Chromosomal Location
ChrIX:41825 to 45952 | ORF Map | GBrowse
Gene Ontology Annotations All BNR1 GO evidence and references
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 3 genes
Classical genetics
Large-scale survey
175 total interaction(s) for 112 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 9
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 1
  • Protein-peptide: 1
  • Reconstituted Complex: 9
  • Two-hybrid: 50

Genetic Interactions
  • Dosage Rescue: 20
  • Negative Genetic: 30
  • Phenotypic Enhancement: 19
  • Phenotypic Suppression: 3
  • Positive Genetic: 6
  • Synthetic Growth Defect: 5
  • Synthetic Haploinsufficiency: 1
  • Synthetic Lethality: 10
  • Synthetic Rescue: 10

Expression Summary
Length (a.a.) 1,375
Molecular Weight (Da) 156,850
Isoelectric Point (pI) 7.94
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIX:41825 to 45952 | ORF Map | GBrowse
Last Update Coordinates: 1994-12-10 | Sequence: 1994-12-10
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..4128 41825..45952 1994-12-10 1994-12-10
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000001421

The S. cerevisiae genome encodes two genes that are members of the formin family, BNI1 and BNR1, which assemble linear actin cables in the bud and bud neck, respectively (3). Formins are a conserved family of proteins that promote the assembly of actin filaments, a function that is necessary for remodeling of the actin cytoskeleton during such processes as budding, mating, cytokinesis, endocytosis, and in higher cells, cell adhesion and migration. The hallmark of formin proteins is the presence of two highly conserved FH (formin homology) domains: the FH1 domain, containing polyproline motifs that mediate binding to profilin, which in turn binds actin monomers; and the FH2 domain, which nucleates actin assembly (reviewed in 4 and 5). Bni1p and Bnr1p are classified in the diaphanous-related formin (DRF) group of metazoan formins, named for the founding Drosophila gene diaphanous (dia) (6). The FH2 domains of Bni1p and Bnr1p are distinct from those of the metazoan groups, containing a yeast-specific insert that is not found in other organisms (7). In addition to FH1 and FH2 domains, DRFs also contain a regulatory Rho-binding domain (RBD) and a Dia-autoregulatory-domain (DAD) (reviewed in 5). Null mutations in either BNI1 or BNR1 do not impair cell viability, but the double bni1 bnr1 mutant is inviable, indicating that formins play an essential role in S. cerevisiae (8).

A model for formin-mediated actin assembly proposes the following sequence of events (reviewed in 9). Activated Rho protein binds to the formin RBD and releases the formin from a conformation in which it is autoinhibited, due to interaction between its amino and carboxy termini, to a conformation that exposes the FH1 and FH2 domains. The FH1 domain interacts with profilin-bound actin monomers, "delivering" them to the FH2 domain, which is dimeric in structure and thus may interact with two actin monomers to stabilize a dimeric actin form, prior to polymerization to form actin cables. The FH2 domain remains associated with the growing end of the filament to protect it from interaction with capping proteins (an FH2 function termed "processive capping").

Consistent with the model, Bnr1p interacts with GTP-bound Rho4p and is thus a potential target (1). Bud14p has also been identified as a regulator of BNR1; Bud14p inhibits the Bnr1p FH2 domain, and displaces Bnr1p from growing ends (10). Bnr1p localizes exclusively to the bud neck, and localization depends on the bud neck-localized septins Cdc3p, Cdc10p, Cdc11p, Cdc12p, and Shs1p (11, 12). At this locale, Bnr1p assembles actin cables that extend from the bud neck into the mother cell and therefore help stabilize the mother-bud axis (3). In vitro experiments have demonstrated that Bnr1p nucleating activity is 10-fold stronger than Bni1p activity, likely due to the fact that Bnr1p has a higher affinity for filament ends than Bni1p; in addition, Bnr1p binds to the sides of actin filaments and bundles them, whereas Bni1p does not (13). Haploid bnr1 null mutant cells exhibit a random budding pattern but grow well at 23, 30, and 37 degrees Celsius (1).

Last updated: 2010-04-23 Contact SGD

References cited on this page View Complete Literature Guide for BNR1
1) Imamura H, et al.  (1997) Bni1p and Bnr1p: downstream targets of the Rho family small G-proteins which interact with profilin and regulate actin cytoskeleton in Saccharomyces cerevisiae. EMBO J 16(10):2745-55
2) Dong Y, et al.  (2003) Formin-dependent actin assembly is regulated by distinct modes of Rho signaling in yeast. J Cell Biol 161(6):1081-92
3) Pruyne D, et al.  (2004) Stable and dynamic axes of polarity use distinct formin isoforms in budding yeast. Mol Biol Cell 15(11):4971-89
4) Goode BL and Eck MJ  (2007) Mechanism and function of formins in the control of actin assembly. Annu Rev Biochem 76():593-627
5) Evangelista M, et al.  (2003) Formins: signaling effectors for assembly and polarization of actin filaments. J Cell Sci 116(Pt 13):2603-11
6) Castrillon DH and Wasserman SA  (1994) Diaphanous is required for cytokinesis in Drosophila and shares domains of similarity with the products of the limb deformity gene. Development 120(12):3367-77
7) Higgs HN and Peterson KJ  (2005) Phylogenetic analysis of the formin homology 2 domain. Mol Biol Cell 16(1):1-13
8) Vallen EA, et al.  (2000) Roles of Hof1p, Bni1p, Bnr1p, and myo1p in cytokinesis in Saccharomyces cerevisiae. Mol Biol Cell 11(2):593-611
9) Moseley JB, et al.  (2006) Formin proteins: purification and measurement of effects on actin assembly. Methods Enzymol 406():215-34
10) Chesarone M, et al.  (2009) Displacement of formins from growing barbed ends by bud14 is critical for actin cable architecture and function. Dev Cell 16(2):292-302
11) Kikyo M, et al.  (1999) An FH domain-containing Bnr1p is a multifunctional protein interacting with a variety of cytoskeletal proteins in Saccharomyces cerevisiae. Oncogene 18(50):7046-54
12) Buttery SM, et al.  (2007) Yeast Formins Bni1 and Bnr1 Utilize Different Modes of Cortical Interaction during the Assembly of Actin Cables. Mol Biol Cell 18(5):1826-38
13) Moseley JB and Goode BL  (2005) Differential activities and regulation of Saccharomyces cerevisiae formin proteins Bni1 and Bnr1 by Bud6. J Biol Chem 280(30):28023-33