Overexpression of Gcs1-myc, but not Gcs1-zn-myc, caused dissociation of endogenous Arl1p from trans-Golgi. Gcs1-myc overexpression affected the distribution of Arl1p. Gcs1-mycpVT101U was transformed into gcs1 cells with or without GFP-Sft2pRS314. Mid-log phase cells overexpressing Gcs1-myc were stained with anti-myc, anti-GFP, affinity-purified anti-Arl1p, or affinity-purified anti-Arf1p antibody.