Participation of Xenopus Elr-type Proteins in Vegetal mRNA Localization during Oogenesis

Abstract

Directional transport of specific mRNAs is of primary biological relevance. In Xenopus oocytes, mRNA localization to the vegetal pole is important for germ layer formation and germ cell development. Using a biochemical approach, we identified Xenopus Elr-type proteins, homologs of the Hu/ELAV proteins, as novel components of the vegetal mRNA localization machinery. They bind specifically to the localization elements of several different vegetally localizing Xenopus mRNAs, and they are part of one RNP together with other localization proteins, such as Vg1RBP and XStaufen 1. Blocking Elr-type protein binding by either localization element mutagenesis or antisense morpholino oligonucleotide-mediated masking of their target RNA structures, as well as overexpression of wild type and mutant ElrB proteins, interferes with vegetal localization in Xenopus oocytes.

Heterogeneous Nuclear Ribonucleoprotein (hnRNP) F Is a Novel Component of Oligodendroglial RNA Transport Granules Contributing to Regulation of Myelin Basic Protein (MBP) Synthesis

“…Relative cDNA levels were quantified by real time-PCR using a onestep real time-PCR system and the TaqMan assays Mm01225301_m1, Mm00607939_s1, and Mm01266402_m1 (all Applied Biosystems). The relative enrichment of mRNAs in the hnRNP F-myc and control IPs was calculated as described before (30). In individual experiments the enrichment factor of MBP and ␤-actin mRNAs was normalized to the enrichment factor of phosphoglycerate kinase 1 mRNA.…”

Functional dissection of the RNA signal sequence responsible for vegetal localization ofXGrip2.1mRNA in Xenopus oocytes

“…2B). In contrast to XGrip2.1 and XDead end-LEs, the Vg1LE exhibits only weak binding activities for ElrA and B (similar differential binding activities to ElrA and B have previously been shown by comparative UV-crosslinking analysis 21 ). Binding activities of the Vg1LE to 40LoVe and VgRBP60 were to the formation of nuclear localization RNPs.…”

“…[35][36][37][38] Consistent with this observation, early pathway localization elements were shown to interact with Vg1RBP, VgRBP60 and ElrA/B in vitro, factors that are assigned to the late transport pathway and which may thus also be required for late localization of early pathway RNAs. 17,21,33 The ability of early pathway LEs to localize via the late pathway might reflect a mechanism that ensures the vegetal localization of early pathway RNAs that did not enter the early pathway on time. Conversely, localization elements from late pathway RNAs were also found to accumulate in the mitochondrial cloud after injection into stage I oocytes, and competition studies indicate that early and late pathway RNAs might compete for localization factors in vivo, with LEs from early pathway RNAs having higher affinities for these factors than the late pathway LEs.…”

“…[22][23][24] A structural reorganization of such localization RNPs occurs in the cytoplasm and includes the recruitment of cytoplasmic localization factors such as XStaufen 1/2, Prrp and ElrA/B. 18,21,22,25,26 The Plus-end directed transport of localization particles along microtubules is mediated by overlapping functions of Kinesin I and II motor proteins. 27,28 The anchoring of RNAs at the vegetal cortex depends on micro-and intermediate filaments as well as on localizing RNAs themselves, such as xlsirts and VegT, which are required to maintain the structural organization of cortical cytokeratin filaments.…”

DND1 (DND microRNA-mediated repression inhibitor 1)

“…Celf interacts with the late element (LE) of Dnd RNA. LE of Dnd mRNA also interacts with Elavl1 and Elav2 (Arthur et al, 2009).…”