Key result
The Myo4p globular tail, together with an N-terminal linker region, is required for efficient She3p binding and proper ASH1 mRNA localization in yeast.
The Myo4p globular tail is essential for ASH1 mRNA localization and She3p binding in yeast, challenging previous studies that suggested it was not required.
Challenges prior yeast models of Myo4p function; leaves open conservation in mammalian mRNA transport.
Type V myosin (MyoV)-dependent transport of cargo is an essential process in eukaryotes. Studies on yeast and vertebrate MyoV showed that their globular tails mediate binding to the cargo complexes. In Saccharomyces cerevisiae, the MyoV motor Myo4p interacts with She3p to localize asymmetric synthesis of HO 1 (ASH1) mRNA into the bud of dividing cells. A recent study showed that localization of GFP-MS2-tethered ASH1 particles does not require the Myo4p globular tail, challenging the supposed role of this domain. We assessed ASH1 mRNA and Myo4p distribution more directly and found that their localization is impaired in cells expressing globular tail-lacking Myo4p. In vitro studies further show that the globular tail together with a more N-terminal linker region is required for efficient She3p binding. We also determined the x-ray structure of the Myo4p globular tail and identify a conserved surface patch important for She3p binding. The structure shows pronounced similarities to membrane-tethering complexes and indicates that Myo4p may not undergo auto-inhibition of its motor domain.
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Heuck et al. (2010) studied this question. Myo4p globular tail deletion vs. Wild-type Myo4p was evaluated on ASH1 mRNA and Myo4p distribution and She3p binding. The Myo4p globular tail, together with an N-terminal linker region, is required for efficient She3p binding and proper ASH1 mRNA localization in yeast.
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