High-copy suppressor analysis reveals a physical interaction between Sec34p and Sec35p, a protein implicated in vesicle docking.
A temperature-sensitive mutant, sec34-2, is defective in the late stages of endoplasmic reticulum (ER)-to-Golgi transport. A high-copy suppressor screen that uses the sec34-2 mutant has resulted in the identification of the SEC34 structural gene and a novel gene called GRP1. GRP1 encodes a previously unidentified hydrophilic yeast protein related to the mammalian Golgi protein golgin-160. Although GRP1 is not essential for growth, the grp1Delta mutation displays synthetic lethal interactions with several mutations that result in ER accumulation and a block in the late stages of ER-to-Golgi transport, but not with those that block the budding of vesicles from the ER. Our findings suggest that Grp1p may facilitate membrane traffic indirectly, possibly by maintaining Golgi function. In an effort to identify genes whose products physically interact with Sec34p, we also tested the ability of overexpressed SEC34 to suppress known secretory mutations that block vesicular traffic between the ER and the Golgi. This screen revealed that SEC34 specifically suppresses sec35-1. SEC34 encodes a hydrophilic protein of approximately 100 kDa. Like Sec35p, which has been implicated in the tethering of ER-derived vesicles to the Golgi, Sec34p is predominantly soluble. Sec34p and Sec35p stably associate with each other to form a multiprotein complex of approximately 480 kDa. These data indicate that Sec34p acts in conjunction with Sec35p to mediate a common step in vesicular traffic.
Kim
D W
DW
Howard Hughes Medical Institute and the Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Sacher
M
M
Scarpa
A
A
Quinn
A M
AM
Ferro-Novick
S
S
D000595:Amino Acid Sequence; D001324:Autoantigens / Q000737:chemistry; D002268:Carboxypeptidases / Q000378:metabolism; D002352:Carrier Proteins; D043402:Cathepsin A; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D013489:Suppression, Genetic; D033921:Vesicular Transport Proteins; D015003:Yeasts / Q000235:genetics*
D001324:Autoantigens; C112749:COG2 protein, S cerevisiae; D002352:Carrier Proteins; D005656:Fungal Proteins; C108388:GOLGA3 protein, human; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; C400547:RUD3 protein, S cerevisiae; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C040985:phosphatidylinositol receptors; D002268:Carboxypeptidases; D043402:Cathepsin A