2024-03-29T08:19:46Z
http://docs.lib.purdue.edu/do/oai/
oai:docs.lib.purdue.edu:ocspub-1001
2007-03-22T14:33:53Z
publication:ocs
publication:dp
publication:ocspub
The mitogenic function of hepatitis B virus X protein resides within amino acids 51 to 140 and is modulated by N- and C-terminal regulatory regions
Li, H
Chi, C Y
Lee, S
Andrisani, O M
The hepatitis B virus (HBV) X protein (pX) is implicated in hepatocarcinogenesis by an unknown mechanism. pX variants encoded by HBV genomes found integrated in genomic DNA from liver tumors of patients with hepatocellular carcinoma (HCC) generally lack amino acids 134 to 154. Since deregulation of mitogenic pathways is linked to oncogenic transformation, herein we define the pX region required for mitogenic pathway activation. A series of pX deletions was used to construct tetracycline-regulated pX-expressing cell lines. The activation of the mitogenic pathways by these pX deletions expressed in the constructed cell lines was measured by transient transreporter assays, effects on endogenous cyclin A expression, and apoptosis. Conditional expression of pX51-140 in AML12 clone 4 cell line activates the mitogenic pathways, induces endogenous cyclin A expression, and sensitizes cells to apoptosis, similar to wild-type (WT) pX. By contrast, pX1-115 is inactive, supporting the idea that amino acids 116 to 140 are required for mitogenic pathway activation. Moreover, this pX deletion analysis demonstrates that WT pX function is modulated by two regions spanning amino acids 1 to 78 and 141 to 154. The N-terminal X1-78, expressed via a retroviral vector in WT pX-expressing 4pX-1 cells, coimmunoprecipitates with WT pX, indicating this pX region participates in protein-protein interactions leading to pX oligomerization. Interestingly, pX1-78 interferes with WT pX in mediating mitogenic pathway activation, endogenous gene expression, and apoptosis. The C-terminal pX region spanning amino acids 141 to 154 decreases pX stability, determined by pulse-chase studies of WT pX and pX1-140, suggesting that increased stability of naturally occurring pX variants lacking amino acids 134 to 154 may play a role in HCC development.
2006-08-08T07:00:00Z
Article
https://docs.lib.purdue.edu/ocspub/2
oai:docs.lib.purdue.edu:ocspub-1002
2007-03-26T18:43:16Z
publication:dp
publication:engr
publication:ocs
publication:nanopub
publication:nano
publication:ocspub
publication:ece
publication:ecepubs
Ambipolar conduction in transistors using solution grown InAs nanowires with Cd doping
Hang, Qingling
Wang, Fudong
Buhro, William E
Janes, David B
Nanowire field effect transistors have been fabricated using Cd doped InAs nanowires synthesized using a solution-liquid-solid technique. Both n-channel and p-channel characteristics have been observed, which implies that the surface Fermi level is not pinned in the conduction band. The observation of a p channel is attributed to the passivation of surface states by surface ligands introduced during nanowire synthesis and to the effects of heavy acceptor doping. Devices in which the surface ligands are removed by O-2 plasma treatment exhibit only n-channel conduction, which would be consistent with surface Fermi level pinning in the conduction band. (c) 2007 American Institute of Physics.
SEMICONDUCTOR NANOWIRES; ACCUMULATION; SURFACES
2007-03-26T07:00:00Z
Article
https://docs.lib.purdue.edu/ocspub/3
oai:docs.lib.purdue.edu:ocspub-1003
2007-03-26T19:03:16Z
publication:dp
publication:ocs
publication:ocspub
Microfluidic cell fusion under continuous direct current voltage
Wang, Jun
Lu, Chang
The authors report a technique which produces cell-to-cell electrofusion using a common direct current power supply on a microfluidic platform. In the authors' method, the cells were first conjugated based on biotin-streptavidin interaction. The electrofusion was then conducted by flowing the linked cells through a simple microfluidic channel with geometric variation under continuous direct current voltage. This microfluidics-based technique offers processing at the level of single cell pairs with efficiency comparable to that of conventional electrofusion technique based on electrical pulses. (c) 2006 American Institute of Physics.
ELECTROFUSION; ELECTROPHORESIS; HYBRIDIZATION; DEVICE
2007-03-26T07:00:00Z
Article
https://docs.lib.purdue.edu/ocspub/4
oai:docs.lib.purdue.edu:ocspub-1004
2007-03-26T19:25:08Z
publication:dp
publication:ocs
publication:ocspub
Minimum length requirement of the flexible N-terminal translocation subdomain of colicin E3
Sharma, Onkar
Cramer, William A
The 315-residue N-terminal T domain of colicin E3 functions in translocation of the colicin across the outer membrane through its interaction with outer membrane proteins including the OmpF porin. The first 83 residues of the T domain are known from structure studies to be disordered. This flexible translocation subdomain contains the TolB box (residues 34 to 46) that must cross the outer membrane in an early translocation event, allowing the colicin to bind to the TolB protein in the periplasm. In the present study, it was found that cytotoxicity of the colicin requires a minimum length of 19 to 23 residues between the C terminus (residue 46) of the TolB box and the end of the flexible subdomain (residue 83). Colicin E3 molecules of sufficient length display normal binding to TolB and occlusion of OmpF channels in vitro. The length of the N-terminal subdomain is critical because it allows the TolB box to cross the outer membrane and interact with TolB. It is proposed that the length constraint is a consequence of ordered structure in the downstream segment of the T domain (residues 84 to 315) that prevents its insertion through the outer membrane via a translocation pore that includes OmpF.
ESCHERICHIA-COLI K-12; OUTER-MEMBRANE; CRYSTAL-STRUCTURE; CROSS-RESISTANCE; IMMUNITY PROTEIN; CELL ENTRY; OMPF PORIN; IN-VITRO; GROUP-A; DOMAIN
2007-03-26T07:00:00Z
Article
https://docs.lib.purdue.edu/ocspub/5
oai:docs.lib.purdue.edu:ocspub-1006
2007-03-26T19:48:45Z
publication:dp
publication:ocs
publication:ocspub
The maturation of mucus-secreting gastric epithelial progenitors into digestive-enzyme secreting zymogenic cells requires Mist1
Ramsey, Victoria G
Doherty, Jason M
Chen, Christopher C.
Stappenbeck, Thaddeus S
Konieczny, Stephen F
Mills, Jason C
Continuous regeneration of digestive enzyme (zymogen)-secreting chief cells is a normal aspect of stomach function that is disrupted in precancerous lesions ( e. g. metaplasias, chronic atrophy). The cellular and genetic pathways that underlie zymogenic cell (ZC) differentiation are poorly understood. Here, we describe a gene expression analysis of laser capture microdissection purified gastric cell populations that identified the bHLH transcription factor Mist1 as a potential ZC regulatory factor. Our molecular and ultrastructural analysis of proliferation, migration and differentiation of the gastric unit in Mist1(-/-) and control mice supports a model whereby wild-type ZC progenitors arise as neck cells in the proliferative (isthmal) zone of the gastric unit and become transitional cells (TCs) with molecular and ultrastructural characteristics of both enzyme-secreting ZCs and mucus-secreting neck cells as they migrate to the neck-base zone interface. Thereafter, they rapidly differentiate into mature ZCs as they enter the base. By contrast, Mist1(-/-) neck cells differentiate normally, but ZCs in the mature, basal portion of the gastric unit uniformly exhibit multiple apical cytoplasmic structural abnormalities. This defect in terminal ZC differentiation is also associated with markedly increased abundance of TCs, especially in late-stage TCs that predominantly have features of immature ZCs. Thus, we present an in vivo system for analysis of ZC differentiation, present molecular evidence that ZCs differentiate from neck cell progenitors and identify Mist1 as the first gene with a role in this clinically important process.
Bhlhb8; mucous neck cell; laser-capture microdissection; microarray; mouse; TRANSCRIPTION FACTOR MIST1; SEROUS EXOCRINE CELLS; MOUSE STOMACH; GASTROINTESTINAL-TRACT; PARIETAL-CELLS; NECK CELLS; CORPUS; DYNAMICS; CANCER; MICE
2007-03-26T07:00:00Z
Article
https://docs.lib.purdue.edu/ocspub/7
oai:docs.lib.purdue.edu:ocspub-1005
2007-03-26T19:35:14Z
publication:dp
publication:ocs
publication:ocspub
Acm1 is a negative regulator of the Cdh1-dependent anaphase-promoting complex/cyclosome in budding yeast
Martinez, Juan S
Jeong, Dah-Eun
Choi, Eunyoung
Billings, Brian M
Hall, Mark C
Cdh1 is a coactivator of the anaphase-promoting complex/cyclosome (APC/C) and contributes to mitotic exit and G(1) maintenance by facilitating the polyubiquitination and subsequent proteolysis of specific substrates. Here, we report that budding yeast Cdh1 is a component of a cell cycle-regulated complex that includes the 14-3-3 homologs Bmh1 and Bmh2 and a previously uncharacterized protein, which we name Acm1 (Apc/c(Cdh1) modulator 1). Association of Cdh1 with Bmh1 and Bmh2 requires Acm1, and the Acm1 protein is cell cycle regulated, appearing late in G(1) and disappearing in late M. In acm1 Delta strains, Cdh1 localization to the bud neck and association with two substrates, Clb2 and Hsl1, were strongly enhanced. Several lines of evidence suggest that Acm1 can suppress APC/C-Cdh1-mediated proteolysis of mitotic cyclins. First, overexpression of Acm1 fully restored viability to cells expressing toxic levels of Cdh1 or a constitutively active Cdh1 mutant lacking inhibitory phosphorylation sites. Second, overexpression of Acm1 was toxic in sic1 Delta cells. Third, ACM1 deletion exacerbated a low-penetrance elongated-bud phenotype caused by modest overexpression of Cdh1. This bud elongation was independent of the morphogenesis checkpoint, and the combination of acm1 Delta and hsl1 Delta resulted in a dramatic enhancement of bud elongation and G(2)/M delay. Effects on bud elongation were attenuated when Cdh1 was replaced with a mutant lacking the C-terminal IR dipeptide, suggesting that APC/C-dependent proteolysis is required for this phenotype. We propose that Acm1 and Bmh1/Bmh2 constitute a specialized inhibitor of APC/C-Cdh1.
APC-DEPENDENT PROTEOLYSIS; MITOTIC CYCLIN CLB2; SACCHAROMYCES-CEREVISIAE; CELL-CYCLE; S-PHASE; SUBSTRATE RECOGNITION; PHOSPHATASE CDC14; DESTRUCTION BOX; KINASE CDC28; COMPLEX
2007-03-26T07:00:00Z
Article
https://docs.lib.purdue.edu/ocspub/6