DNA primase activity from human lymphocytes. Synthesis of oligoribonucleotides that prime DNA synthesis.

Unfractionated or T-cell-enriched human lymphocytes can be stimulated to undergo DNA synthesis and mitosis by the addition of polyclonal cell activators such as the plant lectins phytohaemagglutinin and concanavalin A (ConA). Under conventional culture conditions stimulated cells cease proliferating only a few days after the first cells have initiated DNA synthesis. Cytochalasin B (CB), which is non-mitogenic per se, causes a prolongation of the period during which ConA stimulates DNA synthesis from normally 3–5 days to more than 3 weeks. The CB-induced prolongation of cell proliferation is clearly stage-specific in the sense that the CB effects are exerted after an initial period of 24 h and do not come into effect until 48 h after onset of ConA stimulation. In contrast, CB exerts a slight suppressive action on DNA synthesis between 24 h (when activated cells initiate DNA synthesis) and 48 h after onset of stimulation. These two separate effects of CB, i.e. augmentation of lymphocyte stimulation 48 h after stimulation, and suppression of stimulation before this point of time, are relatively independent of the concentration of CB.

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The effects of phorbol ester and Ca ionophore on c-fos and c-myc expression and on DNA synthesis in human lymphocytes are not directly related

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(87)91130-2 ◽

1987 ◽

Vol 148 (1) ◽

pp. 435-442 ◽

Cited By ~ 13

Author(s):

Alain Pompidou ◽

Marisol Corral ◽

Paule Michel ◽

Nicole Defer ◽

Jacques Kruh ◽

...

Keyword(s):

Dna Synthesis ◽

Phorbol Ester ◽

Human Lymphocytes

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The protein synthetic surge in response to mitogen triggers high glycolytic enzyme levels in human lymphocytes and occurs prior to DNA synthesis

Biochemical Medicine and Metabolic Biology ◽

10.1016/0885-4505(90)90073-a ◽

1990 ◽

Vol 44 (3) ◽

pp. 282-291 ◽

Cited By ~ 6

Author(s):

Trygve O. Tollefsbol ◽

Harvey Jay Cohen

Keyword(s):

Dna Synthesis ◽

Human Lymphocytes ◽

Glycolytic Enzyme

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Damage by Dichlorvos of Human Lymphocyte DNA

Tumori Journal ◽

10.1177/030089168006600403 ◽

1980 ◽

Vol 66 (4) ◽

pp. 425-430 ◽

Cited By ~ 5

Author(s):

Paolo Perocco ◽

Angela Fini

Keyword(s):

Dna Synthesis ◽

Human Lymphocyte ◽

Tritiated Thymidine ◽

Human Lymphocytes ◽

Ultraviolet Rays ◽

Thymidine Uptake ◽

Short Term ◽

In Vitro System ◽

Tritiated Thymidine Uptake

The action of dichlorvos (2.2-dichlorovinyldimethyl phosphate) was studied with a short-term in vitro system which utilizes human lymphocytes. The parameters studied were the action exerted by the pesticide on scheduled (semiconservative) and unscheduled (reparative) DNA synthesis measured as tritiated thymidine uptake. The results obtained show that dichlorvos affects semiconservative DNA synthesis, damages human lymphocyte DNA inducing low reparative synthesis, and interferes with DNA repair processes after damage exerted by ultraviolet rays.

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Primer release is the rate-limiting event in lagging-strand synthesis mediated by the T7 replisome

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1604894113 ◽

2016 ◽

Vol 113 (21) ◽

pp. 5916-5921 ◽

Cited By ~ 8

Author(s):

Alfredo J. Hernandez ◽

Seung-Joo Lee ◽

Charles C. Richardson

Keyword(s):

Dna Synthesis ◽

Dna Polymerase ◽

Fragment Length ◽

Dna Binding Protein ◽

Okazaki Fragment ◽

Dna Primase ◽

Dna Strands ◽

Leading Strand ◽

Rate Limiting ◽

Lagging Strand

DNA replication occurs semidiscontinuously due to the antiparallel DNA strands and polarity of enzymatic DNA synthesis. Although the leading strand is synthesized continuously, the lagging strand is synthesized in small segments designated Okazaki fragments. Lagging-strand synthesis is a complex event requiring repeated cycles of RNA primer synthesis, transfer to the lagging-strand polymerase, and extension effected by cooperation between DNA primase and the lagging-strand polymerase. We examined events controlling Okazaki fragment initiation using the bacteriophage T7 replication system. Primer utilization by T7 DNA polymerase is slower than primer formation. Slow primer release from DNA primase allows the polymerase to engage the complex and is followed by a slow primer handoff step. The T7 single-stranded DNA binding protein increases primer formation and extension efficiency but promotes limited rounds of primer extension. We present a model describing Okazaki fragment initiation, the regulation of fragment length, and their implications for coordinated leading- and lagging-strand DNA synthesis.

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