Brown D D, Schlissel M S
Cell. 1985 Oct;42(3):759-67. doi: 10.1016/0092-8674(85)90272-7.
Somatic 5S RNA genes are transcribed preferentially over oocyte 5S RNA genes by 25- to greater than 200-fold when mixtures of cloned genes are injected into cleaving Xenopus embryos. This preference is an order of magnitude greater than that observed in cell-free extracts. Mutations that decrease the binding of the 5S RNA gene-specific transcription factor TFIIIA to the 5S RNA genes' internal control regions are exaggerated when assayed by embryo injection compared to in vitro transcription. Injection of TFIIIA into cleaving embryos greatly increases endogenous oocyte 5S RNA synthesis at midblastula even when DNA replication is inhibited. Much, but not all, of the preference for somatic over oocyte 5S RNA gene transcription in somatic cells can thus be attributed to the concentration of TFIIIA and to differences in binding constants of TFIIIA to the internal control regions of the two types of genes.
当将克隆基因混合物注射到分裂期的非洲爪蟾胚胎中时，体细胞5S RNA基因的转录优先于卵母细胞5S RNA基因，其转录倍数为25倍至大于200倍。这种偏好比在无细胞提取物中观察到的情况高一个数量级。与体外转录相比，当通过胚胎注射进行检测时，降低5S RNA基因特异性转录因子TFIIIA与5S RNA基因内部控制区结合的突变会被放大。即使在DNA复制受到抑制的情况下，将TFIIIA注射到分裂期胚胎中也会大大增加囊胚中期内源性卵母细胞5S RNA的合成。因此，体细胞中对体细胞5S RNA基因转录而非卵母细胞5S RNA基因转录的偏好，很大程度上（但不是全部）可归因于TFIIIA的浓度以及TFIIIA与这两种基因内部控制区结合常数的差异。
