Bleomycin Affects CellWallAnchorage ofMannoproteins inSaccharomyces cerevisiae

Bleomycin induces strand breakage inDNA through disruption ofglycosidic linkages. We investigated the ability ofbleomycin todamageyeastcell walls, whicharecomposed primarily ofcarbohydrate. Bleomycin treatment ofintact yeast cells facilitated enzymatic conversion ofyeasts tospheroplasts. Bleomycin treatment also altered anchorage ofmannoproteins tothecell wallmatrix inintact cells orisolated cell walls. Cellsurface mannoproteins were labelled with12.5, andtheir solubilization wasmonitored. Seventeen hourtreatments with bleomycin released some ofthelabeldirectly intotreatment supernatants andfacilitated extraction of mannoproteins bydithiothreitol andlytic enzymes.Bleomycin treatments asshort as10mincaused changes in extraction ofmannoproteins fromintact cells. Specifically, cell wallanchorage ofseveral mannoproteins was affected bythedrug.Therewere drug-induced changes inextractability ofmannoproteins withapparent molecular weights of96,000, 80,000, 61,000, 41,000,31,500, and21,000 (determined after deglycosylation with endo-N-acetylglucosaminidase H).Thesimilarity ofresults obtained inthepresenceandabsence ofcycloheximide, theappearanceofcell walleffects after only10minoftreatment, andthesimilarity ofeffects inintact cells andisolated cell walls areconsistent withdirect drug-induced damageandinconsistent withamechanism dependent on expression ofbleomycin-damaged genesor otherintracellular mediators. Theresults are consistent withbleomycin-mediated increases incellwallpermeability through disruption ofglycosidic cross-linking structures inthecell wall.