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We investigated the spatial variation in the stress fields of Kyushu Island, southwestern Japan. Kyushu Island is characterized by active volcanoes (Aso, Unzen, Kirishima, and Sakurajima) and a shear zone (western extension of the median tectonic line). Shallow earthquakes frequently occur not only along active faults but also in the central region of the island, which is characterized by active volcanoes. We evaluated the focal mechanisms of the shallow earthquakes on Kyushu Island to determine the relative deviatoric stress field. Generally, the stress field was estimated by using the method proposed by Hardebeck and Michael (2006) for the strike-slip regime in this area. The minimum principal compression stress (σ3), with its near north-south trend, is dominant throughout the entire region. However, the σ 3 axes around the shear zone are rotated normal to the zone. This result is indicative of shear stress reduction at the zone and is consistent with the right-lateral fault behavior along the zone detected by a strain-rate field analysis with global positioning system data. Conversely, the stress field of the normal fault is dominant in the Beppu-Shimabara area, which is located in the central part of the island. This result and the direction of σ3 are consistent with the formation of a graben structure in the area.

Chaperonin containing TCP-1 (CCT) is a large multisubunit complex that mediates protein folding in eukaryotic cells. CCT participates in the folding of newly synthesized polypeptides, including actin, tubulin, and several cell cycle regulators; therefore, CCT plays an important role in cytoskeletal organization and cell division. Here we identify the chaperonin CCT as a novel physiological substrate for p90 ribosomal S6 kinase (RSK) and p70 ribosomal S6 kinase (S6K). RSK phosphorylates the ␤ subunit of CCT in response to tumor promoters or growth factors that activate the Ras-mitogen-activated protein kinase (MAPK) pathway. CCT␤ Ser-260 was identified as the RSK site by mass spectrometry and confirmed by site-directed mutagenesis. RSK-dependent Ser-260 phosphorylation was sensitive to the MEK inhibitor UO126 and the RSK inhibitor BID-1870. Insulin weakly activates RSK but strongly activates the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway and utilizes S6K to regulate CCT␤ phosphorylation. Thus, the Ras-MAPK and PI3K-mTOR pathways converge on CCT␤ Ser-260 phosphorylation in response to multiple agonists in various mammalian cells. We also show that RNA interference-mediated knockdown of endogenous CCT␤ causes impaired cell proliferation that can be rescued with ectopically expressed murine CCT␤ wild-type or phosphomimetic mutant S260D, but not the phosphorylation-deficient mutant S260A. Although the molecular mechanism of CCT␤ regulation remains unclear, our findings demonstrate a link between oncogene and growth factor signaling and chaperonin CCT-mediated cellular activities.The molecular mass ϳ90-kDa ribosomal S6 kinases (RSK) 4 and molecular mass ϳ70-kDa ribosomal S6 kinases (S6K) are distinct families of Ser/Thr kinases that regulate diverse cellular processes. RSK is activated by extracellular-signal-regulated kinase (ERK) in the Ras-mitogen-activated protein kinase (MAPK) pathway (1, 2). RSK phosphorylates a variety of proteins, including transcription factors, immediate-early gene products, translational regulators, enzymes, and structural proteins, that potentially link it to many biological processes such as cell proliferation, cell differentiation, and survival (3). S6K acts as a downstream mediator of mammalian target of rapamycin (mTOR) in the phosphoinositide 3-kinase (PI3K) pathway and/or the Ras-MAPK pathway, and regulates cell growth. A number of S6K substrates identified so far include factors involved in the regulation of mRNA translation, highlighting an important role of S6K in protein synthesis (4). Recent studies have revealed that RSK and S6K collaboratively regulate various biological processes, including translational control.Translational control is modulated by various extracellular stimuli. Signaling pathways regulate efficient assembly of components of the translational machinery and also stimulate ribosome biogenesis to facilitate efficient protein synthesis (5-7). The PI3K-mTOR pathway plays a critical role in this process, whereas the Ras-MAPK path...