scholarly journals Characterization of DNA end joining in a mammalian cell nuclear extract: junction formation is accompanied by nucleotide loss, which is limited and uniform but not site specific.

1994 ◽  
Vol 14 (1) ◽  
pp. 170-180 ◽  
Author(s):  
A L Nicolás ◽  
C S Young
Keyword(s):  
Mammalian Cell ◽  
Mammalian Cells ◽  
Nuclear Extract ◽  
Major Effect ◽  
Cell Nuclei ◽  
Site Specific ◽  
Preferential Formation ◽  
Nuclear Extracts ◽  
Dna Substrates ◽  
Molecular And Biochemical Mechanisms

Mammalian cells have a marked capacity to repair double-strand breaks in DNA, but the molecular and biochemical mechanisms underlying this process are largely unknown. A previous report has described an activity from mammalian cell nuclei that is capable of multimerizing blunt-ended DNA substrates (R. Fishel, M.K. Derbyshire, S.P. Moore, and C.S.H. Young, Biochimie 73:257-267, 1991). In this report, we show that nuclear extracts from HeLa cells contain activities which preferentially join linear plasmid substrates in either a head-to-head or tail-to-tail configuration, that the joining reaction is covalent, and that the joining is accompanied by loss of sequence at the junction. Sequencing revealed that there was a loss of a uniform number of nucleotides from junctions formed from any one type of substrate. The loss was not determined by any simple site-specific mechanism, but the number of nucleotides lost was affected by the precise terminal sequence. There was no major effect on the efficiency or outcome of the joining reaction with substrates containing blunt ends or 3' or 5' protruding ends. Using a pair of plasmid molecules with distinguishable restriction enzyme sites, we also observed that blunt-ended DNA substrates could join with those containing protruding 3' ends. As with the junctions formed between molecules with identical ends, there was uniform loss of nucleotides. Taken together, the data are consistent with two models for the joining reaction in which molecules are aligned either throughout most of their length or by using small sequence homologies located toward their ends. Although either model can explain the preferential formation of head-to-head and tail-to-tail products, the latter predicts the precise lossof nucleotides observed. These activities are found in all cell lines examined so far and most likely represent an important repair activity of the mammalian cell.

Characterization of DNA end joining in a mammalian cell nuclear extract: junction formation is accompanied by nucleotide loss, which is limited and uniform but not site specific

1994 ◽  
Vol 14 (1) ◽  
pp. 170-180
Author(s):  
A L Nicolás ◽  
C S Young
Keyword(s):  
Mammalian Cell ◽  
Mammalian Cells ◽  
Nuclear Extract ◽  
Major Effect ◽  
Cell Nuclei ◽  
Site Specific ◽  
Preferential Formation ◽  
Nuclear Extracts ◽  
Dna Substrates ◽  
Molecular And Biochemical Mechanisms

Mammalian cells have a marked capacity to repair double-strand breaks in DNA, but the molecular and biochemical mechanisms underlying this process are largely unknown. A previous report has described an activity from mammalian cell nuclei that is capable of multimerizing blunt-ended DNA substrates (R. Fishel, M.K. Derbyshire, S.P. Moore, and C.S.H. Young, Biochimie 73:257-267, 1991). In this report, we show that nuclear extracts from HeLa cells contain activities which preferentially join linear plasmid substrates in either a head-to-head or tail-to-tail configuration, that the joining reaction is covalent, and that the joining is accompanied by loss of sequence at the junction. Sequencing revealed that there was a loss of a uniform number of nucleotides from junctions formed from any one type of substrate. The loss was not determined by any simple site-specific mechanism, but the number of nucleotides lost was affected by the precise terminal sequence. There was no major effect on the efficiency or outcome of the joining reaction with substrates containing blunt ends or 3' or 5' protruding ends. Using a pair of plasmid molecules with distinguishable restriction enzyme sites, we also observed that blunt-ended DNA substrates could join with those containing protruding 3' ends. As with the junctions formed between molecules with identical ends, there was uniform loss of nucleotides. Taken together, the data are consistent with two models for the joining reaction in which molecules are aligned either throughout most of their length or by using small sequence homologies located toward their ends. Although either model can explain the preferential formation of head-to-head and tail-to-tail products, the latter predicts the precise lossof nucleotides observed. These activities are found in all cell lines examined so far and most likely represent an important repair activity of the mammalian cell.

scholarly journals Serine/threonine phosphatase 1 modulates the subnuclear distribution of pre-mRNA splicing factors.

1996 ◽  
Vol 7 (10) ◽  
pp. 1559-1572 ◽  
Author(s):  
T Misteli ◽  
D L Spector
Keyword(s):  
Rna Polymerase Ii ◽  
Mammalian Cell ◽  
Cell Nucleus ◽  
Nuclear Extract ◽  
Mrna Splicing ◽  
Splicing Factors ◽  
Cell Nuclei ◽  
Nuclear Speckles ◽  
Permeabilized Cells

HeLa cell nuclei were permeabilized and reconstituted with nuclear extract to identify soluble nuclear factors which play a role in the organization of pre-mRNA splicing factors in the mammalian cell nucleus. Permeabilized nuclei reconstituted with nuclear extract were active in transcription and DNA replication and nuclear speckles containing pre-mRNA splicing factors were maintained over several hours independent of soluble nuclear components. The characteristic rounding up of nuclear speckles in response to inhibition of RNA polymerase II seen in vivo was reproduced in permeabilized cells and was strictly dependent on a catalytic activity present in the nuclear extract. By inhibitor titration experiments and sensitivity to inhibitor 2, this activity was identified as a member of the serine/threonine protein phosphatase 1 family (PP1). Interference with PP1 activity affected the distribution of pre-mRNA splicing factors in transcriptionally active, permeabilized cells, and excess PP1 activity caused increased dephosphorylation of SR proteins in nuclear speckles. These data show that the dynamic reorganization of the mammalian cell nucleus can be studied in permeabilized cells and that PP1 is involved in the rounding up of speckles as well as the overall organization of pre-mRNA splicing factors in the mammalian cell nucleus.

scholarly journals Site-Specific Glycosylation of Recombinant Viral Glycoproteins Produced in Nicotiana benthamiana

2021 ◽  
Vol 12 ◽  
Author(s):  
Emmanuel Margolin ◽  
Joel D. Allen ◽  
Matthew Verbeek ◽  
Michiel van Diepen ◽  
Phindile Ximba ◽  
...  
Keyword(s):  
Mammalian Cell ◽  
Nicotiana Benthamiana ◽  
Mammalian Cells ◽  
Large Scale ◽  
Molecular Farming ◽  
Marburg Virus ◽  
Viral Envelope ◽  
Scale Production ◽  
Site Specific ◽  
Viral Glycoproteins

There is an urgent need to establish large scale biopharmaceutical manufacturing capacity in Africa where the infrastructure for biologics production is severely limited. Molecular farming, whereby pharmaceuticals are produced in plants, offers a cheaper alternative to mainstream expression platforms, and is amenable to rapid large-scale production. However, there are several differences along the plant protein secretory pathway compared to mammalian systems, which constrain the production of complex pharmaceuticals. Viral envelope glycoproteins are important targets for immunization, yet in some cases they accumulate poorly in plants and may not be properly processed. Whilst the co-expression of human chaperones and furin proteases has shown promise, it is presently unclear how plant-specific differences in glycosylation impact the production of these proteins. In many cases it may be necessary to reproduce features of their native glycosylation to produce immunologically relevant vaccines, given that glycosylation is central to the folding and immunogenicity of these antigens. Building on previous work, we transiently expressed model glycoproteins from HIV and Marburg virus in Nicotiana benthamiana and mammalian cells. The proteins were purified and their site-specific glycosylation was determined by mass-spectrometry. Both glycoproteins yielded increased amounts of protein aggregates when produced in plants compared to the equivalent mammalian cell-derived proteins. The glycosylation profiles of the plant-produced glycoproteins were distinct from the mammalian cell produced proteins: they displayed lower levels of glycan occupancy, reduced complex glycans and large amounts of paucimannosidic structures. The elucidation of the site-specific glycosylation of viral glycoproteins produced in N. benthamiana is an important step toward producing heterologous viral glycoproteins in plants with authentic human-like glycosylation.

scholarly journals Defective Brca2 influences topoisomerase I activity in mammalian cells.

2003 ◽  
Vol 50 (1) ◽  
pp. 139-144 ◽  
Author(s):  
Iwonna Rahden-Staroń ◽  
Maria Szumiło ◽  
Emilia Grosicka ◽  
Maria Kraakman van der Zwet ◽  
Małgorzata Z Zdzienicka
Keyword(s):  
Mammalian Cells ◽  
Topoisomerase I ◽  
Chinese Hamster ◽  
Brca2 Gene ◽  
Nuclear Extract ◽  
Chinese Hamster Cell ◽  
V79 Cells ◽  
Cell Mutant ◽  
Relaxation Activity ◽  
Nuclear Extracts

The Chinese hamster cell mutant V-C8 is defective in the Brca2 gene (Kraakman-van der Zwet et al., 2002, Cell Biol.; 22: 669). Here we report that V-C8 cells were 10-fold more sensitive to camptothecin, an inhibitor of topoisomerase I, than the parental V79 cells. The level of the relaxation activity of topoisomerase I in nuclear extracts was also lower (4-fold) in V-C8 than V79 cells, in spite of the fact that the level of the topoisomerase I protein was the same in these cells. The survival of V-C8 cells in the presence of camptothecin, the sensitivity of V-C8 topoisomerase I to camptothecin, and the level of the relaxation activity in V-C8 nuclear extract were almost completely restored by transfection of V-C8 cells with the murine Brca2 gene or by the transfer of human chromosome 13 providing the BRCA2 gene. These results indicate that the observed changes in the topoisomerase I activity in V-C8 are due to the defective function of the Brca2 gene.

Site-Specific Identification of Lysine Acetylation Stoichiometries in Mammalian Cells

2016 ◽  
Vol 15 (3) ◽  
pp. 1103-1113 ◽  
Author(s):  
Tong Zhou ◽  
Ying-hua Chung ◽  
Jianji Chen ◽  
Yue Chen
Keyword(s):  
Mammalian Cells ◽  
Lysine Acetylation ◽  
Site Specific ◽  
Specific Identification

Detection and characterization of a factor which rescues spliceosome assembly from a heat-inactivated HeLa cell nuclear extract

1991 ◽  
Vol 11 (7) ◽  
pp. 3425-3431
Author(s):  
P Delannoy ◽  
M H Caruthers
Keyword(s):  
Heat Treatment ◽  
Hela Cell ◽  
Nuclear Extract ◽  
Mrna Splicing ◽  
Splicing Factor ◽  
Nuclear Extracts ◽  
Small Nuclear Rnas ◽  
A Minor ◽  
Cell Nuclear Extract

Mild heat treatment of HeLa cell nuclear extracts (NE) selectively inhibits pre-mRNA splicing. Heat-inactivated extracts can be complemented by a small amount of untreated NE. Utilizing this complementation assay and a combination of ion-exchange, affinity, and hydrophobic chromatography, a heat reversal factor (HRF) was purified from NE that is required to rescue pre-mRNA splicing from a heat-inactivated extract. This activity in its most purified form consistently copurified in a fraction containing two 70-kDa proteins and a minor polypeptide of approximately 100 kDa. It was free of the major small nuclear RNAs, sensitive to protease, and required to rescue spliceosome formation from a heat-inactivated nuclear extract. These results suggest that this factor is a protein that may be an important component in pre-mRNA splicing, or alternatively, it may be involved in renaturation of a heat-sensitive splicing factor.

scholarly journals Identification and Characterization of ART-27, a Novel Coactivator for the Androgen Receptor N Terminus

2002 ◽  
Vol 13 (2) ◽  
pp. 670-682 ◽  
Author(s):  
Steven M. Markus ◽  
Samir S. Taneja ◽  
Susan K. Logan ◽  
Wenhui Li ◽  
Susan Ha ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Transcriptional Activation ◽  
Mammalian Cells ◽  
Hybrid Approach ◽  
Independent Manner ◽  
Activation Domains ◽  
Cell Library ◽  
Nuclear Extracts ◽  
N Terminus ◽  
Transcriptional Activation Domains

The androgen receptor (AR) is a ligand-regulated transcription factor that stimulates cell growth and differentiation in androgen-responsive tissues. The AR N terminus contains two activation functions (AF-1a and AF-1b) that are necessary for maximal transcriptional enhancement by the receptor; however, the mechanisms and components regulating AR transcriptional activation are not fully understood. We sought to identify novel factors that interact with the AR N terminus from an androgen-stimulated human prostate cancer cell library using a yeast two-hybrid approach designed to identify proteins that interact with transcriptional activation domains. A 157-amino acid protein termed ART-27 was cloned and shown to interact predominantly with the AR153–336, containing AF-1a and a part of AF-1b, localize to the nucleus and increase the transcriptional activity of AR when overexpressed in cultured mammalian cells. ART-27 also enhanced the transcriptional activation by AR153–336 fused to the LexA DNA-binding domain but not other AR N-terminal subdomains, suggesting that ART-27 exerts its effect via an interaction with a defined region of the AR N terminus. ART-27 interacts with AR in nuclear extracts from LNCaP cells in a ligand-independent manner. Interestingly, velocity gradient sedimentation of HeLa nuclear extracts suggests that native ART-27 is part of a multiprotein complex. ART-27 is expressed in a variety of human tissues, including sites of androgen action such as prostate and skeletal muscle, and is conserved throughout evolution. Thus, ART-27 is a novel cofactor that interacts with the AR N terminus and plays a role in facilitating receptor-induced transcriptional activation.

Sign in / Sign up

Export Citation Format

Share Document