Larson D E, Hoffmann I, Zahradka P, Birnstiel M L, Sells B H
Department of Molecular Biology and Genetics, College of Biological Science, University of Guelph, Canada.
Biochim Biophys Acta. 1992 Jun 15;1131(2):139-44. doi: 10.1016/0167-4781(92)90068-b.
The capacity for 3' processing of the histone H4 pre-mRNA is lost following differentiation of rat L6 myoblasts to myotubes. Nuclear extracts prepared from proliferating myoblasts, but not differentiated myotubes, actively process histone H4 pre-mRNA in vitro. The activity of two factors required for 3' processing, the heat-labile factor and U7 snRNP, also changes during the differentiation period, concurrent with the loss of 3' processing activity. During myotube formation, the activity of the heat-labile factor decreases significantly while the 5' sequences of the U7 snRNA become progressively resistant to micrococcal nuclease digestion. Thus, the dramatic down-shift in histone H4 mRNA levels which occurs during myoblast differentiation is controlled at both the transcriptional and posttranscriptional level.
大鼠L6成肌细胞分化为肌管后，组蛋白H4前体mRNA的3'加工能力丧失。从增殖的成肌细胞而非分化的肌管中制备的核提取物，能够在体外积极加工组蛋白H4前体mRNA。3'加工所需的两种因子——热不稳定因子和U7 snRNP的活性，在分化期间也会发生变化，这与3'加工活性的丧失同时出现。在肌管形成过程中，热不稳定因子的活性显著降低，而U7 snRNA的5'序列对微球菌核酸酶消化的抗性逐渐增强。因此，成肌细胞分化过程中组蛋白H4 mRNA水平的显著下调在转录和转录后水平均受到调控。
