Within the cell, several mechanisms exist to maintain homeostasis of the endoplasmic reticulum (ER). One of the primary mechanisms is the unfolded protein response (UPR). In this review, we primarily focus on the latest signal webs and regulation mechanisms of the UPR. The relationships among ER stress, apoptosis, and cancer are also discussed. Under the normal state, binding immunoglobulin protein (BiP) interacts with the three sensors (protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1α (IRE1α)). Under ER stress, misfolded proteins interact with BiP, resulting in the release of BiP from the sensors. Subsequently, the three sensors dimerize and autophosphorylate to promote the signal cascades of ER stress. ER stress includes a series of positive and negative feedback signals, such as those regulating the stabilization of the sensors/BiP complex, activating and inactivating the sensors by autophosphorylation and dephosphorylation, activating specific transcription factors to enable selective transcription, and augmenting the ability to refold and export. Apart from the three basic pathways, vascular endothelial growth factor (VEGF)-VEGF receptor (VEGFR)-phospholipase C-γ (PLCγ)-mammalian target of rapamycin complex 1 (mTORC1) pathway, induced only in solid tumors, can also activate ATF6 and PERK signal cascades, and IRE1α also can be activated by activated RAC-alpha serine/threonine-protein kinase (AKT). A moderate UPR functions as a pro-survival signal to return the cell to its state of homeostasis. However, persistent ER stress will induce cells to undergo apoptosis in response to increasing reactive oxygen species (ROS), Ca 2+ in the cytoplasmic matrix, and other apoptosis signal cascades, such as c-Jun N-terminal kinase (JNK), signal transducer and activator of transcription 3 (STAT3), and P38, when cellular damage exceeds the capacity of this adaptive response.

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Bacterium strain PJ3, isolated from wastewater and identified as Arthrobacter sp. bacterium based on its 16S rDNA gene, could use carbazole as the sole carbon, nitrogen and energy source. The genomic library of strain PJ3 was constructed and a positive clone JM109 (pUCW402) was screened out for the expression of dioxygenase by the ability to form yellow ring-fission product. A 2,3-dihydroxybiphenyl dioxygenase (23DHBD) gene of 933 bp was found in the 3360 bp exogenous fragment of pUCW402 by GenSCAN software and BLAST analysis. The phylogenetic analysis showed that 23DHBD from strain PJ3 formed a deep branch separate from a cluster containing most known 23DHBD in GenBank. Southern hybridization confirmed for the first time that the 23DHBD gene was from the genomic DNA of Arthrobacter sp. PJ3. In order to test the gene function, recombinant bacterium BL21 (pETW-8) was constructed to express 23DHBD. The expression level in BL21 (pETW-8) was highest compared with the recombinant bacteria JM109 (pUCW402) and strain PJ3. We observed that 23DHBD was not absolute specific. The enzyme activity was higher with 2,3-dihydroxybiphenyl as a substrate than with catechol. The substrate specificity assay suggested that 23DHBD was essential for cleavage of bi-cyclic aromatic compounds during the course of aromatic compound biodegradation in Arthrobacter sp. strain PJ3.2,3-dihydroxybiphenyl dioxygenase gene, Arthrobacter sp., phylogenetic tree, gene location, enzyme activity A number of plants synthesize an array of complex aromatic compounds and in some cases these substances or derived compounds may be released to the environment [1] . Aromatic compounds are thermally and chemically stable, persisting in the environment and accumulating as pollutants [2] . Mutations of microorganisms in the environment occur to alter their capacity to decompose these compounds into energy, carbon and nitrogen source to survive. Microbial degradation is thus an attractive means to remove aromatic compounds from the environment. Bacterial ring cleavage dioxygenases play a key role in degrading aromatic compounds for re-entry into the carbon cycle [3] and are of particular commercial interest because of their potential to effectively substitute chemical methods currently used in a variety of applications, especially environmental remediation of pollutants [4] .The major pathway for polychlorinated biphenyl (PCB) degradation is initiated by biphenyl dioxygenase, and the 3rd step is a meta-cleavage of the aromatic ring. This step is catalyzed by 2,3-dihydroxybiphenyl dioxygenase (23DHBD) which catalyzes the conversion of 2,3-dihydroxybiphenyl to 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) with the insertion of two atoms of oxygen [5] . 23DHBD has been found in various biphenyl-utilizing bacteria such as Beijerinckia sp. strain B1 [6] , Rhodococcus globerulus strain P6 [7] , and Sphingomonas sp. strain BN6 [8] .

The presence of actin in the nucleus as well as its functions in various nuclear processes has been made clear in the past few years. Actin is known to be a part of chromatin-remodeling complexes BAF, which are required for maximal ATPase activity of the Brg1 component of the BAF complex. Moreover, the essential roles of actin in transcription mediated by RNA polymerases I, II and III have been demonstrated recently. On the other hand, a myosin I isoform, which contains a unique NH2-terminal extension for nucleus localization, has been specifically localized in nucleus. As is well known, myosin I is an actin-binding protein and plays an important role in various cellular activities. Though actin and nuclear myosin I (NM I) have been implicated to play distinct roles in gene expression, there has been no evidence for the actin-myosin interaction that might be involved in gene transcription mediated by RNA polymerase II (RNAP II). Here we show evidence that both actin and NM I are associated with RNAP II in nucleus by using co-localization and co-IP assays, and they may act together on gene transcription. The antibodies against β-actin or NM I can block RNA synthesis in a eukaryotic in vitro transcription system with template DNA comprising the promoter and the coding region of human autocrine motility factor receptor (hAMFR) gene; the antibodies pre-adsorbed with purified actin and NM I have no effect in transcriptional inhibition, indicating that the inhibition of transcription by anti-actin and anti-NM I is specific. These results suggest a direct involvement of actin-myosin complexes in regulating tran- scription. It also implicates that actin and NM I may co-exist in a same complex with RNAP II and the interaction of RNAP II with actin and NM I functions in the RNAP II-mediated transcription.actin, nuclear myosin I, RNAP II, gene transcription RNAP II directed transcription is a complex and highly regulated process in which the chromatin remodeling, the formation of preinitiation complexes, the binding of transcription factors to regulatory regions of DNA and the recruitment of the RNAP II complex to the preinitiation complexes are the prerequisites for transcription initiation, and a huge number of proteins contribute to the process by orchestrated interplays. The presence of actin in nucleus as well as its functions in various nuclear processes such as nucleocytoplasmic transport, chromatin remodeling, transcription, and splicing has been well established in the past few years. Actin is known to be a part of chromatin remodeling complex BAF and required for the maximal ATPase activity of BRG1, a component of the BAF complex [1] . In G. tentans, actin binds to hrp65, a nuclear protein associated with mRNP complexes, and the binding is required for transcription on polytene chromosome [2] . Moreover, the incorporation of bromouridine-triphosphate into nascent transcription could be inhibited by both RNAi-mediated depletion of hnRNP U and disruption of the actin-hnRNP U complex [3] . Importantly, actin could be...