Müller F, Wicky C, Spicher A, Tobler H
Institute of Zoology, University of Fribourg, Switzerland.
Cell. 1991 Nov 15;67(4):815-22. doi: 10.1016/0092-8674(91)90076-b.
During the process of chromatin diminution, which takes place in all presomatic cells of the early Ascaris embryo, the heterochromatic termini of the chromosomes are lost. Here we show that the newly formed ends of the reduced somatic chromosomes carry tandem repeats of the telomeric sequence TTAGGC. Comparison of a cloned somatic telomere with the corresponding germline chromosomal region revealed that these telomeric repeats are not present at or near the chromosomal breakage site. They are most likely added by a telomerase-mediated event. Chromosomal breakage, which precedes the telomere addition process, takes place within a short, specific chromosomal region (CBR); however, it does not occur at a single locus, but rather at many different sites. Altogether, our data show that chromatin diminution in Ascaris is a complex molecular process that includes site-specific chromosomal breakage, new telomere formation, and DNA degradation.
在染色质消减过程中，早期蛔虫胚胎的所有前体细胞都会发生这种情况，染色体的异染色质末端会丢失。我们在此表明，经消减后的体细胞染色体新形成的末端带有端粒序列TTAGGC的串联重复序列。将克隆的体细胞端粒与相应的种系染色体区域进行比较发现，这些端粒重复序列在染色体断裂位点或其附近并不存在。它们很可能是由端粒酶介导的事件添加的。在端粒添加过程之前发生的染色体断裂发生在一个短的特定染色体区域（CBR）内；然而，它并非发生在单个位点，而是发生在许多不同的位点。总之，我们的数据表明蛔虫中的染色质消减是一个复杂的分子过程，包括位点特异性染色体断裂、新端粒形成和DNA降解。
