Effects of inhibition of basement membrane collagen deposition on rat mammary gland development |
| |
Authors: | MS Wicha LA Liotta BK Vonderhaar WR Kidwell |
| |
Institution: | Laboratory of Pathophysiology, National Cancer Institute, Bethesda, Maryland 20205 |
| |
Abstract: | DNA biosynthesis by a system containing giant nuclei isolated from rat trophoblast cells at Day 13 of pregnancy has been studied. A method for the isolation of giant nuclei in good yield has been described. These nuclei were capable of incorporating 3H]dTTP into DNA for 2 hr and the incorporation was proportional to the amount of DNA template (nuclei). The system was highly dependent on the four deoxyribonucleoside triphosphates, ATP, and Mg2+ and was stimulated by monovalent ions such as K+. The optimum pH was 8.6. The product of the reaction was insensitive to RNase, sensitive to DNase, and banded at 1.710 g/ml in neutral CsCl together with bulk rat trophoblast DNA. Pulse-chase and density labeling experiments utilizing bromodeoxyuridine have indicated that replicative, discontinuous synthesis was taking place at sites previously active in vivo. DNA polymerases α, β, and γ were shown to be present in the nuclei. Experiments utilizing selective inhibitors of polymerases have demonstrated that DNA replication by trophoblast nuclei in vitro was insensitive to the specific α-polymerase inhibitor, aphidicolin, but almost completely inhibited by 2′, 3′-dideoxythymidine 5′-triphosphate as well as by N-ethylmaleimide suggesting that DNA replication observed in these trophoblast nuclei in vitro may be carried out by DNA polymerase γ. |
| |
Keywords: | To whom correspondence and requests for reprints should be addressed |
本文献已被 ScienceDirect 等数据库收录! |
|