title: The yeast homologue of the microtubule-associated protein Lis1 interacts with the sumoylation machinery and a SUMO-targeted ubiquitin ligase.
abstract: Microtubules and microtubule-associated proteins are fundamental for multiple cellular processes, including mitosis and intracellular motility, but the factors that control microtubule-associated proteins (MAPs) are poorly understood. Here we show that two MAPs-the CLIP-170 homologue Bik1p and the Lis1 homologue Pac1p-interact with several proteins in the sumoylation pathway. Bik1p and Pac1p interact with Smt3p, the yeast SUMO; Ubc9p, an E2; and Nfi1p, an E3. Bik1p interacts directly with SUMO in vitro, and overexpression of Smt3p and Bik1p results in its in vivo sumoylation. Modified Pac1p is observed when the SUMO protease Ulp1p is inactivated. Both ubiquitin and Smt3p copurify with Pac1p. In contrast to ubiquitination, sumoylation does not directly tag the substrate for degradation. However, SUMO-targeted ubiquitin ligases (STUbLs) can recognize a sumoylated substrate and promote its degradation via ubiquitination and the proteasome. Both Pac1p and Bik1p interact with the STUbL Nis1p-Ris1p and the protease Wss1p. Strains deleted for RIS1 or WSS1 accumulate Pac1p conjugates. This suggests a novel model in which the abundance of these MAPs may be regulated via STUbLs. Pac1p modification is also altered by Kar9p and the dynein regulator She1p. This work has implications for the regulation of dynein's interaction with various cargoes, including its off-loading to the cortex.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Annabel
authors.initials: A
authors.lastname: Alonso
authors.forename: Sonia
authors.initials: S
authors.lastname: D'Silva
authors.forename: Maliha
authors.initials: M
authors.lastname: Rahman
authors.forename: Pam B
authors.initials: PB
authors.lastname: Meluh
authors.forename: Jacob
authors.initials: J
authors.lastname: Keeling
authors.forename: Nida
authors.initials: N
authors.lastname: Meednu
authors.forename: Harold J
authors.initials: HJ
authors.lastname: Hoops
authors.forename: Rita K
authors.initials: RK
authors.lastname: Miller
mesh_terms: D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008938:Mitosis; D025842:SUMO-1 Protein / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D058207:Sumoylation; D025801:Ubiquitin / Q000235:genetics; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: C488173:Bik1 protein, S cerevisiae; D002352:Carrier Proteins; D008869:Microtubule-Associated Proteins; C464019:NIS1 protein, S cerevisiae; D025842:SUMO-1 Protein; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D004722:Endoribonucleases; C499539:PAC1 protein, S cerevisiae; C506745:ULS1 protein, S cerevisiae; D004265:DNA Helicases