title: Seawi--a sea urchin piwi/argonaute family member is a component of MT-RNP complexes.
abstract: The piwi/argonaute family of proteins is involved in key developmental processes such as stem cell maintenance and axis specification through molecular mechanisms that may involve RNA silencing. Here we report on the cloning and characterization of the sea urchin piwi/argonaute family member seawi. Seawi is a major component of microtubule-ribonucleoprotein (MT-RNP) complexes isolated from two different species of sea urchin, Strongylocentrotus purpuratus and Paracentrotus lividus. Seawi co-isolates with purified ribosomes, cosediments with 80S ribosomes in sucrose density gradients, and binds microtubules. Seawi possesses the RNA binding motif common to piwi family members and binds P. lividus bep4 mRNA, a transcript that co-isolates with MT-RNP complexes and whose translation product has been shown to play a role in patterning the animal-vegetal axis. Indirect immunofluorescence studies localized seawi to the cortex of unfertilized eggs within granule-like particles, the mitotic spindle during cell division, and the small micromeres where its levels were enriched during the early cleavage stage. Lastly, we discuss how seawi, as a piwi/argonaute family member, may play a fundamentally important role in sea urchin animal-vegetal axis formation and stem cell maintenance.
authors.affiliation: Department of Biological Sciences, Rutgers University, 101 Warren Street, 135 Smith Hall, Newark, NJ 07102, USA.
authors.forename: Alexis J
authors.initials: AJ
authors.lastname: Rodriguez
authors.forename: Susan A
authors.initials: SA
authors.lastname: Seipel
authors.forename: Danielle R
authors.initials: DR
authors.lastname: Hamill
authors.forename: Daniele P
authors.initials: DP
authors.lastname: Romancino
authors.forename: Marta
authors.initials: M
authors.lastname: DI Carlo
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Suprenant
authors.forename: Edward M
authors.initials: EM
authors.lastname: Bonder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D018507:Gene Expression Regulation, Developmental; D015723:Gene Library; D008565:Membrane Proteins / Q000235:genetics; D008870:Microtubules / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000145:classification* / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012617:Sea Urchins / Q000145:classification / Q000196:embryology / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: C065555:Bep4 protein, Paracentrotus lividus; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D011506:Proteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins