title: Drosophila Symplekin localizes dynamically to the histone locus body and tricellular junctions.
abstract: The scaffolding protein Symplekin is part of multiple complexes involved in generating and modifying the 3' end of mRNAs, including cleavage-polyadenylation, histone pre-mRNA processing and cytoplasmic polyadenylation. To study these functions in vivo, we examined the localization of Symplekin during development and generated mutations of the Drosophila Symplekin gene. Mutations in Symplekin that reduce Symplekin protein levels alter the efficiency of both poly A(+) and histone mRNA 3' end formation resulting in lethality or sterility. Histone mRNA synthesis takes place at the histone locus body (HLB) and requires a complex composed of Symplekin and several polyadenylation factors that associates with the U7 snRNP. Symplekin is present in the HLB in the early embryo when Cyclin E/Cdk2 is active and histone genes are expressed and is absent from the HLB in cells that have exited the cell cycle. During oogenesis, Symplekin is preferentially localized to HLBs during S-phase in endoreduplicating follicle cells when histone mRNA is synthesized. After the completion of endoreplication, Symplekin accumulates in the cytoplasm, in addition to the nucleoplasm, and localizes to tricellular junctions of the follicle cell epithelium. This localization depends on the RNA binding protein ypsilon schachtel. CPSF-73 and a number of mRNAs are localized at this same site, suggesting that Symplekin participates in cytoplasmic polyadenylation at tricellular junctions.
authors.affiliation: a Department of Biology ; University of North Carolina ; Chapel Hill , NC USA.
authors.forename: Deirdre C
authors.initials: DC
authors.lastname: Tatomer
authors.forename: Lindsay F
authors.initials: LF
authors.lastname: Rizzardi
authors.forename: Kaitlin P
authors.initials: KP
authors.lastname: Curry
authors.forename: Alison M
authors.initials: AM
authors.lastname: Witkowski
authors.forename: William F
authors.initials: WF
authors.lastname: Marzluff
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Duronio
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000235:genetics; D004330:Drosophila; D029721:Drosophila Proteins / Q000096:biosynthesis* / Q000235:genetics; D004625:Embryo, Nonmammalian; D047108:Embryonic Development; D018507:Gene Expression Regulation, Developmental; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D045586:Intranuclear Inclusion Bodies / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D056489:Nucleoplasmins / Q000235:genetics; D026723:Polyadenylation / Q000235:genetics*; D020885:Ribonucleoprotein, U7 Small Nuclear / Q000235:genetics; D016196:S Phase / Q000235:genetics; D039221:mRNA Cleavage and Polyadenylation Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D029721:Drosophila Proteins; D006657:Histones; D056489:Nucleoplasmins; D020885:Ribonucleoprotein, U7 Small Nuclear; C541112:Sym protein, Drosophila; D039221:mRNA Cleavage and Polyadenylation Factors
keywords: CTD, RNA polymerase II C-terminal domain; Drosophila; HCC, histone cleavage complex; HDE, histone downstream element; HLB, histone locus body; Madm, MLF1-adaptor molecule; PAP, poly (A) polymerase; PAS, poly A signal; RNA processing, Symplekin; Rp49, ribosomal protein L32; SL, stem loop; SLBP, stem loop binding protein; Sym, Symplekin; cas, castor; gene expression; histone mRNA; nuclear bodies; sop, ribosomal protein S2; yps, ypsilon schachtel