Tsuda M, Hirose S, Suzuki Y
Mol Cell Biol. 1986 Nov;6(11):3928-33. doi: 10.1128/mcb.6.11.3928-3933.1986.
The addition of exogenous histones has an inhibitory effect on fibroin gene transcription in posterior silk gland extracts. The histones probably disturb a process in complex formation, because when transcription complexes were constructed by preincubation of the templates with the extracts, the inhibitory effect of histones was greatly reduced. Transcription of a fibroin gene construct, pFb5' delta-238, having the upstream region beyond the TATA box was relatively less inhibited than that of pFb5' delta-44 lacking the upstream region. This tendency toward differential inhibition was observed in the silk gland extracts but not in a HeLa cell extract and persisted even after complex formation in the silk gland extracts, suggesting a specific interaction of the upstream region with some factors in the extracts. The complexes formed on pFb5' delta-44 are probably more susceptible to the inhibitory effect of histones. On the basis of these results we propose a participation of the upstream region of the fibroin gene in the formation of stable transcription complexes at the promoter through an interaction with specific factors in the silk gland. Since the transcription-enhancing effect via the upstream region is augmented at a high histone/DNA ratio, it may mimic the in vivo situation in which the fibroin gene can be transcribed in the posterior silk gland even in the presence of excess suppressive materials.
添加外源组蛋白对后部丝腺提取物中的丝心蛋白基因转录具有抑制作用。组蛋白可能干扰了复合物形成过程，因为当通过模板与提取物预孵育构建转录复合物时，组蛋白的抑制作用大大降低。与缺乏上游区域的pFb5'δ-44相比，具有TATA框以外上游区域的丝心蛋白基因构建体pFb5'δ-238的转录受到的抑制相对较小。这种差异抑制的趋势在丝腺提取物中观察到，但在HeLa细胞提取物中未观察到，并且即使在丝腺提取物中形成复合物后仍然存在，这表明上游区域与提取物中的某些因子存在特异性相互作用。在pFb5'δ-44上形成的复合物可能对组蛋白的抑制作用更敏感。基于这些结果，我们提出丝心蛋白基因的上游区域通过与丝腺中的特定因子相互作用参与启动子处稳定转录复合物的形成。由于通过上游区域的转录增强作用在高组蛋白/DNA比例下增强，它可能模拟了体内情况，即即使在存在过量抑制物质的情况下，丝心蛋白基因仍可在后部丝腺中进行转录。
