Essential Features of a Non-processive Class V Myosin from Budding Yeast for ASH1 mRNA Transport

Myo4p, a single-headed and nonprocessive class V myosin in budding yeast, transports >20 different mRNAs asymmetrically to the bud. Here, we determine the features of the Myo4p motor that are necessary for correct localization of ASH1 mRNA to the daughter cell, a process that also requires the adapter protein She3p and the dimeric mRNA-binding protein She2p. The rod region of Myo4p, but not the globular tail, is essential for correct localization of ASH1 mRNA, confirming that the rod contains the primary binding site for She3p. The requirement for both the rod region and She3p can be bypassed by directly coupling the mRNA-binding protein She2p to Myo4p. ASH1 mRNA was also correctly localized when one motor was bound per dimeric She2p, or when two motors were joined together by a leucine zipper. Because multiple mRNAs are cotransported to the bud, it is likely that this process involves multiple motor transport regardless of the number of motors per zip code. Our results show that the most important feature for correct localization is the retention of coupling between all the members of the complex (Myo4p–She3p–She2p–ASH1 mRNA), which is aided by She3p being a tightly bound subunit of Myo4p.

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Pushing for answers: is myosin V directly involved in moving mitochondria?

The Journal of Cell Biology ◽

10.1083/jcb.200803064 ◽

2008 ◽

Vol 181 (1) ◽

pp. 15-18 ◽

Cited By ~ 8

Author(s):

Rajeshwari R. Valiathan ◽

Lois S. Weisman

Keyword(s):

Cell Division ◽

Light Chain ◽

Budding Yeast ◽

Myosin V ◽

Class V ◽

Mitochondrial Transport ◽

Direct Involvement ◽

Cell Biol ◽

Myosin Motors

In budding yeast, the actin-based class V myosin motors, Myo2 and Myo4, transport virtually all organelles from mother to bud during cell division. Until recently, it appeared that mitochondria may be an exception, with studies showing that the Arp2/3 complex is required for their movement. However, several recent studies have proposed that Myo2 has a direct involvement in mitochondria inheritance. In this issue, Altmann et al. (Altmann, K., M. Frank, D. Neumann, S. Jakobs, and B. Westermann. 2008. J. Cell Biol. 181:119–130) provide the strongest support yet that Myo2 and its associated light chain Mlc1 function directly and significantly in both mitochondria–actin interactions and in the movement of mitochondria from mother to bud. The conflicting functions of Arp 2/3 and Myo2 may be reconciled by the existence of multiple pathways involved in mitochondrial transport.

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Association of the class V myosin Myo4p with a localised messenger RNA in budding yeast depends on She proteins

Journal of Cell Science ◽

10.1242/jcs.112.10.1511 ◽

1999 ◽

Vol 112 (10) ◽

pp. 1511-1518 ◽

Cited By ~ 2

Author(s):

S. Munchow ◽

C. Sauter ◽

R.P. Jansen

Keyword(s):

Messenger Rna ◽

Budding Yeast ◽

Motor Protein ◽

Specific Protein ◽

Asymmetric Distribution ◽

Messenger Rnas ◽

Direct Role ◽

Mating Type Switching ◽

Type V ◽

Ash1 Mrna

Asymmetric distribution of messenger RNAs is a widespread mechanism to localize synthesis of specific protein to distinct sites in the cell. Although not proven yet there is considerable evidence that mRNA localisation is an active process that depends on the activity of cytoskeletal motor proteins. To date, the only motor protein with a specific role in mRNA localisation is the budding yeast type V myosin Myo4p. Myo4p is required for the localisation of ASH1 mRNA, encoding a transcriptional repressor that is essential for differential expression of the HO gene and mating type switching in budding yeast. Mutations in Myo4p, in proteins of the actin cytoskeleton, and in four other specific genes, SHE2-SHE5 disrupt the daughter-specific localisation of ASH1 mRNA. In order to understand if Myo4p is directly participating in mRNA transport, we used in situ colocalisation and coprecipitation of Myo4p and ASH1 mRNA to test for their interaction. Our results indicate an association of Myo4p and ASH1 mRNA that depends on the activity of two other genes involved in ASH1 mRNA localisation, SHE2 and SHE3. This strongly suggests a direct role of Myo4p myosin as a transporter of localised mRNAs, convincingly supporting the concept of motor-protein based mRNA localisation.

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A single molecule approach to mRNA transport by a class V myosin

RNA Biology ◽

10.4161/rna.29947 ◽

2014 ◽

Vol 11 (8) ◽

pp. 986-991 ◽

Cited By ~ 2

Author(s):

Thomas E Sladewski ◽

Kathleen M Trybus

Keyword(s):

Single Molecule ◽

Mrna Transport ◽

Class V

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Molecular architecture and dynamics of ASH1 mRNA recognition by its mRNA-transport complex

Nature Structural & Molecular Biology ◽

10.1038/nsmb.3351 ◽

2017 ◽

Vol 24 (2) ◽

pp. 152-161 ◽

Cited By ~ 24

Author(s):

Franziska Theresia Edelmann ◽

Andreas Schlundt ◽

Roland Gerhard Heym ◽

Andreas Jenner ◽

Annika Niedner-Boblenz ◽

...

Keyword(s):

Molecular Architecture ◽

Mrna Transport ◽

Ash1 Mrna ◽

Transport Complex

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The class V myosin motor protein, Myo2, plays a major role in mitochondrial motility in Saccharomyces cerevisiae

The Journal of Cell Biology ◽

10.1083/jcb.200709099 ◽

2008 ◽

Vol 181 (1) ◽

pp. 119-130 ◽

Cited By ~ 72

Author(s):

Katrin Altmann ◽

Martina Frank ◽

Daniel Neumann ◽

Stefan Jakobs ◽

Benedikt Westermann

Keyword(s):

Saccharomyces Cerevisiae ◽

Actin Cytoskeleton ◽

Molecular Mechanisms ◽

Budding Yeast ◽

Motor Protein ◽

Mitochondrial Morphology ◽

Direct Role ◽

Class V ◽

Myosin Motor ◽

Mitochondrial Motility

The actin cytoskeleton is essential for polarized, bud-directed movement of cellular membranes in Saccharomyces cerevisiae and thus ensures accurate inheritance of organelles during cell division. Also, mitochondrial distribution and inheritance depend on the actin cytoskeleton, though the precise molecular mechanisms are unknown. Here, we establish the class V myosin motor protein, Myo2, as an important mediator of mitochondrial motility in budding yeast. We found that mutants with abnormal expression levels of Myo2 or its associated light chain, Mlc1, exhibit aberrant mitochondrial morphology and loss of mitochondrial DNA. Specific mutations in the globular tail of Myo2 lead to aggregation of mitochondria in the mother cell. Isolated mitochondria lacking functional Myo2 are severely impaired in their capacity to bind to actin filaments in vitro. Time-resolved fluorescence microscopy revealed a block of bud-directed anterograde mitochondrial movement in cargo binding–defective myo2 mutant cells. We conclude that Myo2 plays an important and direct role for mitochondrial motility and inheritance in budding yeast.

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