Hancock R L
Canadian Institute of Theoretical Biology, Nova Scotia.
Med Hypotheses. 1993 May;40(5):287-95. doi: 10.1016/0306-9877(93)90008-e.
A search for control mechanisms involving embryonic genes is explored reviewing a variety of subject areas including, a) the methylation status of DNA and the globin gene, b) ethionine and steroid effects on expression of embryonic genes, c) alpha-fetoprotein gene activity induced by carcinogens and in hepatomas. Also taken into account are transcriptional and cytogenetic aspects. Theories of heterochromatin dynamics are developed in connection with certain contributions from chromatin experimental findings, especially regarding the status of methylation. The potential importance to control theory of the inverse correlation between ATP:L-methionine S-adenosyltransferase activity and alpha-fetoprotein synthesis is emphasized. Several generalizations were derived during the study. It appears that the depression mechanisms may act only on genes that have been active in embryonic stages and have become repressed during differentiation. Another idea concerned heterochromatin. Any heterochromatic segment of DNA may represent at its associated ends a certain amount of euchromatin that would be in a quasi-heterochromatic state. Such pseudoheterochromatin is hypothesized to be induced by the true heterochromatin (eigenheterochromatin).
本文通过回顾多个主题领域，探讨了涉及胚胎基因的调控机制，其中包括：a) DNA和珠蛋白基因的甲基化状态；b) 乙硫氨酸和类固醇对胚胎基因表达的影响；c) 致癌物和肝癌中诱导的甲胎蛋白基因活性。同时也考虑了转录和细胞遗传学方面。结合染色质实验结果的某些贡献，特别是关于甲基化状态，发展了异染色质动力学理论。强调了ATP：L-甲硫氨酸S-腺苷转移酶活性与甲胎蛋白合成之间负相关对调控理论的潜在重要性。研究过程中得出了几个一般性结论。似乎抑制机制可能仅作用于在胚胎阶段活跃且在分化过程中被抑制的基因。另一个观点涉及异染色质。任何DNA的异染色质区段在其相关末端可能代表一定量处于准异染色质状态的常染色质。这种假异染色质被假设为由真正的异染色质（固有异染色质）诱导产生。
