MYO4/YAL029C Summary Help

Standard Name MYO4 1
Systematic Name YAL029C
Alias FUN22 2 , SHE1 3
Feature Type ORF, Verified
Description Type V myosin motor involved in actin-based transport of cargos; required for mRNA transport, including ASH1 mRNA, and facilitating the growth and movement of ER tubules into the growing bud along with She3p; MYO4 has a paralog, MYO2, that arose from the whole genome duplication (4, 5 and see Summary Paragraph)
Name Description MYOsin 1
Chromosomal Location
ChrI:92270 to 87855 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All MYO4 GO evidence and references
  View Computational GO annotations for MYO4
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 5 genes
Classical genetics
Large-scale survey
117 total interaction(s) for 55 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 58
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 13
  • Co-crystal Structure: 2
  • Co-fractionation: 4
  • Co-localization: 2
  • Co-purification: 1
  • PCA: 3
  • Protein-RNA: 1
  • Reconstituted Complex: 11
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Growth Defect: 1
  • Dosage Rescue: 2
  • Phenotypic Enhancement: 2
  • Phenotypic Suppression: 1
  • Positive Genetic: 8
  • Synthetic Growth Defect: 3
  • Synthetic Rescue: 1

Expression Summary
Length (a.a.) 1,471
Molecular Weight (Da) 169,342
Isoelectric Point (pI) 7.63
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrI:92270 to 87855 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..4416 92270..87855 2011-02-03 1996-07-31
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 SGDIDS000000027

MYO2 encodes an essential class V myosin heavy chain and MYO4 encodes a second, non-essential, class V myosin (6, 1, 7, 8). Class V myosins are usually homodimers and function as molecular motors that in yeast transport distinct sets of cargo to polarized regions of the cell along actin cables (9, 4). Myo2p predominantly transports membrane-bound organelles, whereas Myo4p moves mRNAs (see below and MYO4). Through evolution Myo4p has lost features found in Myo2p and animal myosins, such as portions of the tail region required for the transport of membrane-bound organelles (9, 10). Still, Myo2p and Myo4p are more closely related to each other than any other myosin. Non-yeast homologs of MYO2 and MYO4 include the mouse dilute gene, chick brain M5a, and the human MYO5A (OMIM), which is mutant in some patients with Griscelli syndrome (9).

Class V myosins have a particular domain architecture and distinct modes of regulation. Myo2p and Myo4p have an N-teminal actin-binding motor domain and a globular C-terminal tail domain separated by a coiled-coil dimerization domain (9). C-terminal to the motor domain is a neck region that contains six IQ motifs that can bind calmodulin encoded by CMD1 (9, 11). Myosins are typically regulated by interactions with light chains. The myosin light chain encoded by MLC1 physically interacts with, and regulates Myo2p (12). The binding of the Myo2p tail by the kinesin-like protein Smy1p promotes the polarized localization of Myo2p and impacts Myo2p function (13, 10, 14, 15). While the light chain(s) that regulate Myo4p are yet to be defined, a novel motor-binding protein, She4p, may modulate Myo4p function (16). Myo2p is phosphorylated in vivo and the functional consequences of these modifications are complex (17).

Myo4p is required for the proper regulation of mating-type switching through its role in transporting ASH1 mRNA to the tip of the bud (3, 18, 19, 20). More recent studies indicate that Myo4p has a general role in transporting mRNAs to the bud-tip (21, 22). mRNAs associate with Myo4p via the She2p and She3p proteins. She3p is an adaptor protein that links Myo4p to its cargo. She2p binds to ASH1 and IST2 mRNAs, while She3p binds to both She2p and Myo4p (23, 24, 21). The ribonucleoprotein complexes are thought to translocate to the bud cortex along actin cables because perturbing actin cables with mutants or drugs disrupts the localization of ASH1 and IST2 mRNAs to the bud (19, 20, and 25).

Myo4p also plays a role in efficient inheritance of the cortical endoplasmic reticulum. She3p, but not She2p, is also required for this process suggesting that Myo4 interacts with its cargos through distinct adapter proteins (26).

Last updated: 2006-10-17 Contact SGD

References cited on this page View Complete Literature Guide for MYO4
1) Haarer BK, et al.  (1994) Identification of MYO4, a second class V myosin gene in yeast. J Cell Sci 107 ( Pt 4)():1055-64
2) Diehl BE and Pringle JR  (1991) Molecular analysis of Saccharomyces cerevisiae chromosome I: identification of additional transcribed regions and demonstration that some encode essential functions. Genetics 127(2):287-98
3) Jansen RP, et al.  (1996) Mother cell-specific HO expression in budding yeast depends on the unconventional myosin myo4p and other cytoplasmic proteins. Cell 84(5):687-97
4) Pruyne D, et al.  (2004) Mechanisms of polarized growth and organelle segregation in yeast. Annu Rev Cell Dev Biol 20:559-91
5) Byrne KP and Wolfe KH  (2005) The Yeast Gene Order Browser: combining curated homology and syntenic context reveals gene fate in polyploid species. Genome Res 15(10):1456-61
6) Johnston GC, et al.  (1991) The Saccharomyces cerevisiae MYO2 gene encodes an essential myosin for vectorial transport of vesicles. J Cell Biol 113(3):539-51
7) Espreafico EM, et al.  (1992) Primary structure and cellular localization of chicken brain myosin-V (p190), an unconventional myosin with calmodulin light chains. J Cell Biol 119(6):1541-57
8) Brown SS  (1997) Myosins in yeast. Curr Opin Cell Biol 9(1):44-8
9) Mermall V, et al.  (1998) Unconventional myosins in cell movement, membrane traffic, and signal transduction. Science 279(5350):527-33
10) Schott D, et al.  (1999) The COOH-terminal domain of Myo2p, a yeast myosin V, has a direct role in secretory vesicle targeting. J Cell Biol 147(4):791-808
11) Brockerhoff SE, et al.  (1994) The unconventional myosin, Myo2p, is a calmodulin target at sites of cell growth in Saccharomyces cerevisiae. J Cell Biol 124(3):315-23
12) Stevens RC and Davis TN  (1998) Mlc1p is a light chain for the unconventional myosin Myo2p in Saccharomyces cerevisiae. J Cell Biol 142(3):711-22
13) Lillie SH and Brown SS  (1994) Immunofluorescence localization of the unconventional myosin, Myo2p, and the putative kinesin-related protein, Smy1p, to the same regions of polarized growth in Saccharomyces cerevisiae. J Cell Biol 125(4):825-42
14) Beningo KA, et al.  (2000) The yeast kinesin-related protein Smy1p exerts its effects on the class V myosin Myo2p via a physical interaction. Mol Biol Cell 11(2):691-702
15) Pashkova N, et al.  (2005) A point mutation in the cargo-binding domain of myosin V affects its interaction with multiple cargoes. Eukaryot Cell 4(4):787-98
16) Wesche S, et al.  (2003) The UCS domain protein She4p binds to myosin motor domains and is essential for class I and class V myosin function. Curr Biol 13(9):715-24
17) Legesse-Miller A, et al.  (2006) Regulated phosphorylation of budding yeast's essential myosin V heavy chain, Myo2p. Mol Biol Cell 17(4):1812-21
18) Bobola N, et al.  (1996) Asymmetric accumulation of Ash1p in postanaphase nuclei depends on a myosin and restricts yeast mating-type switching to mother cells. Cell 84(5):699-709
19) Takizawa PA, et al.  (1997) Actin-dependent localization of an RNA encoding a cell-fate determinant in yeast. Nature 389(6646):90-3
20) Long RM, et al.  (1997) Mating type switching in yeast controlled by asymmetric localization of ASH1 mRNA. Science 277(5324):383-7
21) Takizawa PA, et al.  (2000) Plasma membrane compartmentalization in yeast by messenger RNA transport and a septin diffusion barrier. Science 290(5490):341-4
22) Shepard KA, et al.  (2003) Widespread cytoplasmic mRNA transport in yeast: identification of 22 bud-localized transcripts using DNA microarray analysis. Proc Natl Acad Sci U S A 100(20):11429-34
23) Bohl F, et al.  (2000) She2p, a novel RNA-binding protein tethers ASH1 mRNA to the Myo4p myosin motor via She3p. EMBO J 19(20):5514-24
24) Long RM, et al.  (2000) She2p is a novel RNA-binding protein that recruits the Myo4p-She3p complex to ASH1 mRNA. EMBO J 19(23):6592-601
25) Munchow S, et al.  (1999) Association of the class V myosin Myo4p with a localised messenger RNA in budding yeast depends on She proteins. J Cell Sci 112 ( Pt 10)():1511-8
26) Estrada P, et al.  (2003) Myo4p and She3p are required for cortical ER inheritance in Saccharomyces cerevisiae. J Cell Biol 163(6):1255-66