Abstract:
:Gene amplification may be visualized within a chromosome as a homogeneously stained region (HSR) and HSRs have rarely been reported in human tumor cells with identification of the amplified gene. A parental line and seven clones derived from KB cells resistant to methotrexate (MTX) contain dihydrofolate reductase (DHFR; tetrahydrofolate dehydrogenase; EC 1.5.1.3), ranging from 0.007 unit/mg in the parent to 0.369 unit/mg in clone 7A with a 13,000-fold increase in resistance to MTX. The enzyme is identical to DHFR from other human sources, including that from leukemic patients. A HSR localized to the long arm of chromosome 10(q26) is present in clones selected at or above 2.5 microM MTX. Increase in number of 10q per cell, increase in number of HSR, and increasing amounts of DHFR correlate well. The chromosome change is stable with time as is enzyme production even in the absence of selection by MTX. No clone has shown double minutes. The gene copy number is low. The stability and low gene copy in the presence of large HSRs differ from the pattern described for murine tumors. A human gene for DHFR may be associated with the long arm of chromosome 10.
journal_name
Proc Natl Acad Sci U S Aauthors
Wolman SR,Craven ML,Grill SP,Domin BA,Cheng YCdoi
10.1073/pnas.80.3.807subject
Has Abstractpub_date
1983-02-01 00:00:00pages
807-9issue
3eissn
0027-8424issn
1091-6490journal_volume
80pub_type
杂志文章abstract::Bacterial virulence factors are typically surface-associated or secreted molecules that in Gram-negative bacteria must cross the outer membrane (OM). Protein translocation across the bacterial OM is not well understood. To elucidate this process we studied P pilus biogenesis in Escherichia coli. We present high-resolu...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.6.3146
更新日期:1998-03-17 00:00:00
abstract::A 6.1-kilobase insertion into the rudimentary (r) gene was cloned and partially sequenced. The insertion consists of a 703-base-pair (bp) P element next to a 5.4-kilobase single-copy sequence. The normal position of the single-copy sequence is near the tip of the X chromosome. Upon insertion into the r gene, this chim...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.88.3.693
更新日期:1991-02-01 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.70.10.2879
更新日期:1973-10-01 00:00:00
abstract::Most simian-human immunodeficiency viruses (SHIVs) bearing envelope (Env) glycoproteins from primary HIV-1 strains fail to infect rhesus macaques (RMs). We hypothesized that inefficient Env binding to rhesus CD4 (rhCD4) limits virus entry and replication and could be enhanced by substituting naturally occurring simian...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1606636113
更新日期:2016-06-14 00:00:00
abstract::The mutagenic effect of low linear energy transfer ionizing radiation is reduced for a given dose as the dose rate (DR) is reduced to a low level, a phenomenon known as the direct DR effect. Our reanalysis of published data shows that for both somatic and germ-line mutations there is an opposite, inverse DR effect, wi...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.090099497
更新日期:2000-05-09 00:00:00
abstract::Unfolded RNase A is known to contain an equilibrium mixture of two forms, a slow-folding form (U(1)) and a fast-folding form (U(2)). If U(1) is produced after unfolding by the slow cis-trans isomerization of proline residues about X-Pro imide bonds, then the formation of U(1) should be catalyzed by strong acids. There...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.75.10.4764
更新日期:1978-10-01 00:00:00
abstract::Retroviral gene expression is inhibited in embryonal carcinoma (EC) cells. We have constructed a recombinant retroviral vector that is capable of expressing the neomycin-resistance (neo) gene in EC cells. The critical modification that permits expression of the neo gene is the insertion of a composite simian virus 40 ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.81.22.7137
更新日期:1984-11-01 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1214231110
更新日期:2012-12-26 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.94.2.599
更新日期:1997-01-21 00:00:00
abstract::Exposure of 3T3/A31 cells to serum-free medium, one type of apoptotic stimulus, causes a rapid increase in the sphingosine (Sph) level, which initiates a series of processes: (i) activation of caspase 3 through an enhanced "cascade" of caspases, (ii) release of the C-terminal-half kinase domain of PKCdelta (PKCdelta K...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0406536101
更新日期:2004-10-12 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0510078103
更新日期:2006-01-17 00:00:00
abstract::A codon-optimized mouse LINE-1 element, ORFeus, exhibits dramatically higher retrotransposition frequencies compared with its native long interspersed element 1 counterpart. To establish a retrotransposon-mediated mouse model with regulatable and potent mutagenic capabilities, we generated a tetracycline (tet)-regulat...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1302504110
更新日期:2013-07-16 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1418218112
更新日期:2015-01-13 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.151258398
更新日期:2001-07-31 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0709903105
更新日期:2008-04-08 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1704258114
更新日期:2017-09-05 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0911223107
更新日期:2010-04-27 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.72.8.3255
更新日期:1975-08-01 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.82.22.7706
更新日期:1985-11-01 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
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更新日期:2020-03-24 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
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更新日期:2020-07-21 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1711293115
更新日期:2018-01-30 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0405319101
更新日期:2004-11-16 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.71.12.4965
更新日期:1974-12-01 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.78.5.3133
更新日期:1981-05-01 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1320124110
更新日期:2013-12-03 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.202392199
更新日期:2002-10-01 00:00:00
abstract::A rigorous numerical test of a hypothetical mechanism of a molecular motor should model explicitly the diffusive motion of the motor's degrees of freedom as well as the transition rates between the motor's chemical states. We present such a Brownian dynamics, mechanochemcial model of the coarse-grain structure of the ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0908192106
更新日期:2009-10-27 00:00:00
abstract::We have isolated overlapping phage genomic clones covering an area of 26 kilobases that encodes the human alpha 2-plasmin inhibitor. The alpha 2-plasmin inhibitor gene contains 10 exons and 9 introns distributed over approximately 16 kilobases of DNA. To our knowledge, the number of introns is the highest yet reported...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.18.6836
更新日期:1988-09-01 00:00:00