A new meiosis-specific cohesin complex implicated in the cohesin code for homologous pairingRAD21L is identified as a new meiosis-specific cohesin with a unique spatiotemporal distribution. RAD21L and REC8 have symmetrical, mutually exclusive localization on the not-yet-synapsed homologues, implying that cohesins could establish a code for homologue recognition.

Although parvulin (Par14/eukaryotic parvulin homolog), a peptidyl-prolyl cis-trans isomerase, is found associated with the preribosomal ribonucleoprotein (pre-rRNP) complexes, its roles in ribosome biogenesis remain undetermined. In this study, we describe a comprehensive proteomics analysis of the Par14-associated pre-rRNP complexes using LC-MS/MS and a knockdown analysis of Par14. Together with our previous results, we finally identified 115 protein components of the complexes, including 39 ribosomal proteins and 54 potential trans-acting factors whose yeast homologs are found in the pre-rRNP complexes formed at various stages of ribosome biogenesis. We give evidence that, although Par14 exists in both the phosphorylated and unphosphorylated forms in the cell, only the latter form is associated with the pre-40 S and pre-60 S ribosomal complexes. We also show that Par14 co-localizes with the nucleolar protein B23 during the interphase and in the spindle apparatus during mitosis and that actinomycin D treatment results in the exclusion of Par14 from the nucleolus. Finally we demonstrate that knockdown of Par14 mRNA decelerates the processing of pre-rRNA to 18 and 28 S rRNAs. We propose that Par14 is a component of the pre-rRNA complexes and functions as an rRNA processing factor in ribosome biogenesis. As the amino acid sequence of Par14 including that in the amino-terminal pre-rRNP binding region is conserved only in metazoan homologs, we suggest that its roles in ribosome biogenesis have evolved in the metazoan lineage.

Background: NFATc1 is a necessary and sufficient transcription factor for osteoclastogenesis. Results: JMJD5 negatively regulates NFATc1 protein level through its hydroxylase activity. Conclusion: JMJD5 is a novel osteoclastogenic repressor that induces the degradation of NFATc1 protein.Significance: This study revealed a novel mechanism that regulates NFATc1 activity during osteoclastogenesis.

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Cell cycle-dependent expression of canonical histone proteins enables newly synthesized DNA to be integrated into chromatin in replicating cells. However, the molecular basis of cell cycle-dependency in the switching of histone gene regulation remains to be uncovered. Here, we report the identification and biochemical characterization of a molecular switcher, HERS (histone gene-specific epigenetic repressor in late S phase), for nucleosomal core histone gene inactivation in Drosophila. HERS protein is phosphorylated by a cyclin-dependent kinase (Cdk) at the end of S-phase. Phosphorylated HERS binds to histone gene regulatory regions and anchors HP1 and Su(var)3-9 to induce chromatin inactivation through histone H3 lysine 9 methylation. These findings illustrate a salient molecular switch linking epigenetic gene silencing to cell cycle-dependent histone production.

The BTB domain is a highly conserved protein-protein interaction motif and functions in diverse cellular processes, including transcriptional regulation, ion channel assembly, cytoskeleton dynamics and apoptosis. Recently, it was reported that some BTB domain-containing proteins associate with Cullin-3 (Cul3), an E3 ubiquitin ligase, and act as an adaptor for Cul3 recognition of its substrate. However, the target substrates for the Cul3 ⁄ BTB protein E3 ubiquitin ligase complex are largely unknown. Here, we report the characterization of a novel Drosophila BTB protein, dKLHL18 ⁄ CG3571. By purification of a dKLHL18-associated complex, we identified CG10324, CG5808, l(2)37Cb and dCul3 ⁄ guftagu. Indeed, the physical association of dKLHL18 with these proteins was observed in insect S2 cells, and genetic interactions among the identified factors were also observed in thorax development. Moreover, transient overexpression of dKLHL18 increased the ubiquitinated protein levels of CG10324 and CG5808. These findings suggest that dKLHL18 is an adaptor for a dCul3 E3 ubiquitin ligase to accommodate CG10324, CG5808 and l(2)37Cb proteins for ubiquitination.

The maturation of primary microrRNAs (pri-miRNAs) to precursor miRNAs (pre-miRNAs) is mediated by the "microprocessor" complex minimally comprimising two core components, Drosha and DGCR8. However, the roles of RNA-binding proteins associated with these core units in the large Drosha complex remain to be defined. While signal-dependent regulation of miRNA biogenesis is assumed, such regulation remains to be described. here, we provide a short review based on our recent findings of hormonally-regulated pri-miRNA processing by nuclear estrogen receptor.

Multinucleation is indispensable to the bone-resorbing activity of mature osteoclasts. Nevertheless, little is known about the regulatory networks among multinuclei in a single mature osteoclast. For this reason, we purified osteoclastic factors from the nuclear envelope by two-dimensional gel electrophoresis. Two annexin family proteins and ferritin light chain 1 protein were identified as osteoclastic candidates.Key words: osteoclasts; multinucleation; nuclear envelope; two-dimensional gel electrophoresisOsteoclasts are macrophage-like bone-resorbing cells that differentiate from hematopoietic stem cells. Differentiation is triggered by the actions of several regulators, including a key cytokine, RANKL, and an important transcription factor, NFATc1.1,2) During maturation, precursor cells fuse to produce a giant cell with multiple nuclei. Fully mature osteoclasts bear approximately 20 nuclei.3) Multinucleation appears indispensable to the full function of mature osteoclasts in bone resorption. 4) It has been speculated that communication between nuclei is necessary for mature osteoclastic function. 5)However, the molecular basis of multinucleation and cellular communication among the nuclei within the same cell are not well understood.To address this point, we focused on nuclear envelope proteins, since cellular communication among multinuclei might be mediated by specific proteins on the nuclear surface. In the present study, we identified osteoclastic factors biochemically among nuclear envelope proteins of mouse macrophage-like leukemia monocyte Raw264 cells. This cell line differentiates to multinucleated osteoclasts (MOCs) on treatment with RANKL. Nuclear envelope extracts were prepared from precursors and MOCs following a previous report, as shown in schema 1 (Fig. 1A). 6) MOC formation was confirmed by expression of the cathepsin K (Ctsk) protein, a marker of mature osteoclasts. 7) Likewise, the purity of the cellular fractionation was confirmed by immunoblotting for the following marker proteins: a cytosolic marker (-tubulin) for S1, a nuclear marker (phosphorylated RNA polymerase II on serine 2 [RNAPII-Ser2P]) for S2, and a nuclear envelope marker (laminA) for S3 (Fig. 1B). Although nuclear envelope extracts (S3) of the precursor cells can be partially contaminated by nuclear extracts (S2) (Fig. 1B), 2D gel electrophoresis was performed with the S3 fraction from precursor cells (precursors) and differentiated cells (MOCs). Raw264 cells were treated with GST-RANKL (234 ng/ml, Oriental Yeast, Tokyo, Japan) for 6 d to induce differentiation to mature osteoclasts. A, Schema for the preparation of nuclear envelope extracts. B, Successful fractionation of the extracts was confirmed by immunoblotting with antibodies against the marker proteins: cytosolic extracts, --tubulin (sc-5286; Santa Cruz, Delaware, CA); nuclear extracts, -RNAPII-Ser2P (MMS-129R; Covance, Princeton, NJ); nuclear envelope extracts, -laminA (ab133A2; Abcam, Cambridge, MA). Ctsk (182-12G5; Cosmo Bio, Tokyo, Japan) was used as a MOC marker....