Seidl C, Moritz K B
Zoologisches Institut der Universität, Luisenstrasse 14, 80333 München, Germany.
Nucleic Acids Res. 1998 Feb 1;26(3):768-77. doi: 10.1093/nar/26.3.768.
During the early cleavage period of Ascaris suum , chromatin diminution takes place in the somatic founder cells. In the process of chromatin diminution numerous heterochromatic blocks, consisting predominantly of highly repeated DNA, are discarded during mitotic anaphase and are later on digested in the cytoplasm. Very little is known about proteins that are involved in chromatin diminution. We have detected a nuclear protein and purified it to near homogeneity by its preferential binding to UV-damaged DNA. We termed this protein chromatin diminution associated factor 1 (CDAF1), because maximum binding activity per nucleus was observed to develop in 4-8-cell stages, when chromatin diminution occurs for the first time. CDAF1 recognizes cyclobutane pyrimidine dimers in UV-damaged double-stranded DNA. Its binding properties identify CDAF1 as a novel kind of damaged-DNA binding protein. CDAF1 activity is almost not detectable in 1-celled embryos. It increases dramatically during formation of somatic founder cells and persists up to the first larval stage. However, CDAF1 is absent in tissues of adults. These findings led us to suggest that CDAF1 plays a dual role: during the early segregative cleavage period it might be involved in chromatin diminution as a transfactor and act in nucleotide excision repair as an accessory factor throughout embryogenesis.
在猪蛔虫的早期卵裂期，染色质消减发生在体细胞的起始细胞中。在染色质消减过程中，许多主要由高度重复DNA组成的异染色质块在有丝分裂后期被丢弃，随后在细胞质中被消化。关于参与染色质消减的蛋白质，人们了解甚少。我们检测到一种核蛋白，并通过其与紫外线损伤DNA的优先结合将其纯化至接近同质状态。我们将这种蛋白质称为染色质消减相关因子1（CDAF1），因为在首次发生染色质消减的4-8细胞阶段，每个细胞核的最大结合活性被观察到开始出现。CDAF1识别紫外线损伤的双链DNA中的环丁烷嘧啶二聚体。其结合特性将CDAF1鉴定为一种新型的损伤DNA结合蛋白。在单细胞胚胎中几乎检测不到CDAF1的活性。在体细胞起始细胞形成过程中，它急剧增加，并持续到第一幼虫阶段。然而，在成虫组织中不存在CDAF1。这些发现使我们认为CDAF1具有双重作用：在早期的分离卵裂期，它可能作为一种反式因子参与染色质消减，并在整个胚胎发育过程中作为辅助因子参与核苷酸切除修复。
