Table lists the yeast strains and Table the plasmids used. Sherman 1991 and Ausubel et al. 1996 describe the methods used for growth, maintenance, and genetic manipulation of yeast, and Gietz and Schiestl 1995 describe the method used to transform yeast.
Temperature-sensitive myo2 strains were generated by replacing the 3′ region of the endogenous genomic MYO2 gene with mutagenized plasmid DNA. To construct a plasmid capable of integrating 3′ to MYO2, pJP10-2B (YCp50 containing MYO2) ( Johnston et al. 1991) was cut with SpeI and the resulting fragments circularized using T4 DNA ligase. The ligated DNA served as template for five cycles of amplification by PCR using Taq DNA polymerase and the oligonucleotide primers GATAATGAAATCGATATTATGGAAGA and CGGGATCCATTATCATACTATACTATTGACAAATACTTC. The ClaI-BamHI segment of the 1.7-kb product was inserted into pRS303 ( Sikorski and Hieter 1989). Destruction of the pRS303 SpeI site by cutting with SpeI (partial digest) and XbaI and religation produced the plasmid pRS303MYO2, containing the 201-bp ClaI-SpeI fragment of the MYO2 3′ untranslated region, followed by the 1,587-bp segment of MYO2 from the SpeI site at +3271 on, fused to the sequence GCACTAGA and the NotI site of pRS303.
pRS303MYO2 served as a template for PCR-based mutagenesis ( Cadwell and Joyce 1992), modified to reduce the mutation frequency. The reaction mix (1 mM dCTP, 1 mM dTTP, 0.2 mM dATP, 0.2 mM dGTP, 40 ng pRS303MYO2 cut with PvuII, 7 mM MgCl2, 0.5 mM primers, 50 mM KCl, 10 mM Tris-HCl, pH 8.3, 10 mg BSA, and 0.05% Tween 20; and after the mix had warmed up to 80°C, 0.3 mM MnCl2 and 5u Taq DNA polymerase) was subjected to six cycles of amplification and the EcoRI-NotI fragment of the PCR product was subcloned into the corresponding region of pRS303MYO2 to make libraries of mutagenized MYO2. When cut with SpeI and transformed into yeast, the library plasmids insert pRS303 (containing HIS3) into the ClaI site of the MYO2 3′ untranslated region, and replace the EcoRI-ClaI region of MYO2 with mutagenized sequence encoding amino acid residues 1119 to the COOH terminus.
Roughly 500 transformants at 30°C were replica-plated to 14 and 37°C to detect conditional-lethal mutants. Phloxine B included in plates at 10 mg/liter allowed easier identification of growth-arrested yeast ( Horn and Wilkie 1966). Because dead cells absorb this red dye, red marks correspond to the positions of temperature-sensitive colonies. Genomic DNA from each of the temperature sensitives was cut with SpeI and circularized to reconstitute versions of pRS303MYO2 containing mutations. Transformation of these plasmids relinearized with SpeI into the yeast strain PSY316 yielded the temperature-sensitive strains ABY532, 533, 534, 536, 537, 538, and 530. The temperature sensitivity could be complemented by transformation with pJP10-2B (MYO2 on a low copy number plasmid) or by mating with a MYO2 strain, but could not be complemented by mating with JP7B, a myo2-66 strain. ABY531, an isogenic MYO2 strain, was made by transformation of PSY316 with pRS303MYO2. An analogous series of plasmids made from pRS306 (containing URA3) allowed the construction of yeast strains containing myo2 alleles tagged with URA3. To make an isogenic myo2-66 strain, genomic DNA from JP7B transformed with pRS303MYO2 was cut with NcoI and religated, resulting in an integrating plasmid analogous to pRS303MYO2, but containing the full-length myo2-66 gene instead of the MYO2 fragment. This plasmid was cut with NcoI and transformed into PSY316 to construct ABY535. Diploid versions of these strains were made by transiently transforming with YCp50HO, a plasmid bearing HO ( Herskowitz and Jensen 1991).
Schott D., Ho J., Pruyne D, & Bretscher A. (1999). The Cooh-Terminal Domain of Myo2p, a Yeast Myosin V, Has a Direct Role in Secretory Vesicle Targeting. The Journal of Cell Biology, 147(4), 791-808.