Fission yeast Sop2p: a novel and evolutionarily conserved protein that interacts with Arp3p and modulates profilin function.
Profilins bind to monomeric actin and also interact with ligands such as phosphoinositide 4,5-bisphosphate, the proline-rich protein VASP and a complex of four to six polypeptides identified in Acanthamoeba that includes two actin-related proteins. Here, we report the identification and characterization of an essential gene from Schizosaccharomyces pombe, sop2+, a mutation in which rescues the temperature-sensitive lethality of a profilin mutation, cdc3-124. The sop2-1 mutant is defective for cell elongation and septation, suggesting that it is involved in multiple cortical actin-requiring processes. Consistent with a role in actin cytoskeletal function, negative interactions have been identified between sop2-1 and act1-48, a mutant allele of actin. Sop2p is a novel 377 amino acid polypeptide with similarity to proteins of the beta-transducin repeat family. Sop2p-related proteins have been identified by sequencing projects in diverse species, and we have isolated a human cDNA highly related to sop2+, SOP2 Hs, which functionally complements the sop2-1 mutation. Sop2p proteins from all species contain peptide sequences identical or highly similar to two peptide sequences from an Acanthamoeba beta-transducin repeat protein present in the profilin binding complex. Biochemical analyses demonstrate that Sop2p is present in a complex which also contains the actin-related protein, Arp3p. Immunofluorescence studies reveal the presence of Sop2p in (i) punctate structures distributed throughout the cell, (ii) cables that extend the length of the cell, and (iii) a medial band in a small percentage of septating cells. Collectively these data demonstrate the interaction of Sop2p with Arp3p, profilin and actin.
Balasubramanian
M K
MK
Howard Hughes Medical Institute and Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Feoktistova
A
A
McCollum
D
D
Gould
K L
KL
D000048:Acanthamoeba; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D017124:Conserved Sequence; D003285:Contractile Proteins; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D004330:Drosophila; D005800:Genes, Fungal; D005838:Genotype; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D051304:Profilins; D012441:Saccharomyces cerevisiae; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid
D000199:Actins; D002352:Carrier Proteins; D003285:Contractile Proteins; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D008840:Microfilament Proteins; D051304:Profilins; D029702:Schizosaccharomyces pombe Proteins; C491726:arc1 protein, S pombe