Hamilton J A, Vairo G, Cocks B G
University of Melbourne, Department of Medicine, Royal Melbourne Hospital, Parkville, Australia.
J Immunol. 1992 Jun 15;148(12):4028-35.
Some of the important controlling events regulating eukaryotic S-phase progression are considered to occur late in the G1 stage of the cell cycle. We show here that stimulation of DNA synthesis in bone marrow-derived macrophages (BMM) by macrophage CSF-1 is preceded by G1 expression of three genes which encode proteins associated with the DNA synthesis machinery--the M1 and M2 subunits of ribonucleotide reductase and proliferating cell nuclear Ag (PCNA). Increased expression for these genes correlated well with the mitogenic response and sustained expression required de novo RNA and protein synthesis and also the presence of CSF-1 for at least most of G1. Inhibitors of BMM proliferation (LPS, TNF-alpha, IFN-gamma, and cAMP elevating agents) suppressed CSF-1-induced expression of M1, M2, and PCNA mRNA measured at 22 h. This suppression occurred even when added up to 12 h after the CSF-1, a period coinciding with the G1/S-phase boundary. The delayed kinetics of this effect parallels the ability of these agents to maximally inhibit CSF-1-induced BMM DNA synthesis when added at similar times. Decreased expression of M1, M2, and PCNA was not merely a consequence of DNA synthesis inhibition because the S-phase inhibitor, hydroxyurea, did not suppress CSF-1-induced gene expression. These results suggest that inhibition of DNA synthesis by antiproliferative agents involves inhibition of expression of several genes associated with the DNA synthesis machinery.
一些调控真核生物S期进程的重要控制事件被认为发生在细胞周期的G1期晚期。我们在此表明，巨噬细胞集落刺激因子-1（CSF-1）刺激骨髓来源的巨噬细胞（BMM）中的DNA合成之前，有三个基因在G1期表达，这三个基因编码与DNA合成机制相关的蛋白质——核糖核苷酸还原酶的M1和M2亚基以及增殖细胞核抗原（PCNA）。这些基因表达的增加与促有丝分裂反应密切相关，持续表达需要从头合成RNA和蛋白质，并且在G1期的大部分时间里还需要CSF-1的存在。BMM增殖抑制剂（脂多糖、肿瘤坏死因子-α、干扰素-γ和升高cAMP的试剂）抑制了在22小时时测量的CSF-1诱导的M1、M2和PCNA mRNA的表达。即使在CSF-1加入后长达12小时添加这些抑制剂，这种抑制作用仍然发生，这一时期与G1/S期边界一致。这种效应的延迟动力学与这些试剂在相似时间添加时最大程度抑制CSF-1诱导的BMM DNA合成的能力相似。M1、M2和PCNA表达的降低不仅仅是DNA合成抑制的结果，因为S期抑制剂羟基脲并没有抑制CSF-1诱导的基因表达。这些结果表明，抗增殖剂对DNA合成的抑制涉及对与DNA合成机制相关的几个基因表达的抑制。
