High impact information on MYO4

• We describe the identification of five genes, called SHE1-SHE5, that encode cytoplasmic proteins required for mother-specific HO expression [1].
• She1p, which is identical to the minimyosin Myo4p, and She3p are not, however, mother-specific proteins [1].
• ASH1 encodes a zinc finger protein whose preferential accumulation in daughter cell nuclei at the end of anaphase depends on She1p/Myo4p [2].
• These serve as tracks for the transport of secretory vesicles, the segregation of the trans Golgi network, the vacuole, peroxisomes, endoplasmic reticulum, mRNAs for cell fate determination, and microtubules that orient the nucleus in preparation for mitosis, all by myosin-Vs encoded by the MYO2 and MYO4 genes [3].
• This localization depends on the actin cytoskeleton and five She proteins, one of which is a type V myosin motor, Myo4 [4].

Biological context of MYO4

• The amino acid sequence of CaMYO2 shows 60% identity and 77% homology with MYO2 and 54% identity and 70% homology with MYO4 of budding yeast Saccharomyces cerevisiae, suggesting that CaMYO2 is the only class V myosin in C. albicans [5].
• To identify additional localized mRNAs, we immunoprecipitated the RNA transport components She2p, She3p, and Myo4p and performed DNA microarray analysis of their associated RNAs [6].
• Alterations of MYO4 or MYO2 indicate that neither the motor domains nor tails of these myosins are required to confer the overexpression phenotype, whereas the neck region may be required [7].
• However, overexpression of MYO4 or MYO2 results in several morphological abnormalities, including the formation of short strings of unseparated cells in diploid strains, or clusters of cells in haploid strains [7].

Anatomical context of MYO4

• Subcellular fractionation experiments demonstrate a cosegregation of ER and She2p, which is independent of Myo4p, She3p, or polysomes [8].
• Myo2p and Myo4p constitute respective class V myosins as the heavy chain and, like class V myosins in other organisms, function as actin-based motors for polarized distribution of organelles and intracellular molecules [9].

Other interactions of MYO4

• Consistently, inhibition of nuclear mRNA export results in nuclear accumulation of She2p and cytoplasmic Myo4p mislocalization [10].
• The yeast class V myosins, Myo2p and Myo4p, are nonprocessive actin-based motors [11].

Analytical, diagnostic and therapeutic context of MYO4

• Video microscopy demonstrated that She1p/Myo4p moved particles to the bud tip at 200-440 nm/sec [12].
• A phylogenetic tree was constructed from a sequence alignment by the neighbor-joining method, using Megalign (DNAStar, Madison, WI); the resulting phylogenetic tree showed that squid MyoV is more closely related to vertebrate MyoV (mouse dilute, chicken dilute, rat myr6, and human myo5a) than Drosophila and yeast (myo2, and myo4) myosins V [13].

References