PDGF-RECEPTOR NEGATIVE CELLS

免疫抑制剂对密度阻滞的BALB/c-3 T3细胞的处理 血小板衍生生长的均质或高度纯化的制剂 血小板源性生长因子（PDGF）刺激了几种细胞因子的快速和选择性积累。 通过无细胞翻译鉴定的丰富的mRNA种类。 这些 可翻译的mRNA在进入S期之前很久就出现了。 PDGF较少 选择性mRNA积累比PDGF调节的DNA 合成. 可翻译的mRNAs也在添加了 表皮生长因子，但不是在添加胰岛素或血小板缺乏后 等离子体 它们的选择性积累被添加 放线菌素D 定义了三种类型的PDGF调节的mRNA。 一个 早期（初级）RNA在加入PDGF后30至60分钟内出现; 放线菌酮不能阻断积累。 另一种早期mRNA也 在60分钟内出现，但用PDGF和放线菌酮治疗， 这是最佳积累所必需的。 第三类，次级RNA，开始 在90 ~ 120 min时出现， 由放线菌酮抑制。 单向和双向凝胶电泳 的翻译产物表明， BALB/c-3 T3（ST 2 - 3 T3）细胞系，其不需要PDGF或EGF， 生长，组成性积累的次级生长因子调节 mRNA。 这些可翻译mRNA的积累可能是 PDGF调节的DNA合成。 我们最近利用了一个PDGF调节的溶酶体的cDNA探针， 蛋白（称为MEP）直接定量PDGF调节的mRNA。 PDGF 240 min后开始刺激MEP mRNA的积累 依赖的方式。 其他生长因子，包括EGF，IGF-1，胰岛素， 而贫血小板血浆则没有这种作用。 PDGF调节 环己酰亚胺可抑制MEP mRNA的积累， 需要PDGF调节蛋白质合成。 自发 BALB/c-3 T3细胞的转化变体，其不需要PDGF用于 生长以组成型方式积累MEP mRNA。 因此，MEP 转录物是PDGF调节的二级RNA的实例。 （J）

The treatment of density-arrested BALB/c-3T3 cells with electrophoretically homogenous or highly purified preparations of the platelet-derived growth factor (PDGF) stimulated the rapid and selective accumulation of several species of abundant mRNA identified by cell-free translation. These translatable mRNAs appeared long before entry into the S phase. Less PDGF was required for selective mRNA accumulation than for PDGF-modulated DNA synthesis. The translatable mRNAs also accumulated after addition of the epidermal growth factor but not after addition of insulin or platelet-poor plasma. Their selective accumulation was blocked by addition of actinoimycin D. Three classes of PDGF-modulated mRNAs were defined. An early (primary) RNA appeared within 30 to 60 min of PDGF addition; its accumulation was not blocked by cycloheximide. Another early mRNA also appeared within 60 min, but treatment with both PDGF and cycloheximide was required for optimal accumulation. A third class, secondary RNAs, began to accumulate later at 90 to 120 min; the appearance of this class was inhibited by cycloheximide. One-\and two-dimensional gel electrophoresis of translation products demonstrated that a spontaneously transformed BALB/c-3T3 (ST2-3T3) cell line, which does not require PDGF or EGF for growth, constitutively accumulated the secondary growth factor-regulated mRNAs. The accumulation of these translatable mRNAs may be required for PDGF-modulated DNA synthesis. We have recently utilized a cDNA probe of a PDGF-regulated lysosomal protein (termed MEP) to directly quantify a PDGF-modulated mRNA. PDGF began to stimulate MEP mRNA accumulation 240 min after addition in a dose dependent fashion. Other growth factors, including EGF, IGF-1, insulin, and platelet-poor plasma did not have this effect. The PDGF modulated accumulation of MEP mRNA was inhibitable by cycloheximide demonstrating that PDGF modulated protein synthesis is required. A spontaneously transformed variant of BALB/c-3T3 cells which does not require PDGF for growth accumulated MEP mRNA in a constitutive fashion. Thus the MEP transcript is an example of a PDGF-modulated secondary RNA. (J)