Hotta Y, Tabata S, Stern H
Chromosoma. 1984;90(4):243-53. doi: 10.1007/BF00287031.
A protein having a molecular weight of 73,000 daltons has been purified from the nuclear membranes of preleptotene, leptotene, and zygotene cells. It has been named the leptotene protein (L-protein) because of its role in suppressing the replication of zygotene DNA sequences through leptotene until the initiation of zygotene DNA synthesis. The protein has been found to be highly specific in its inhibitory activity. S-phase replication in somatic nuclei and in microspore nuclei are unaffected by the protein. Only zygotene DNA sequences appear to be affected. L-protein binds specifically to zygotene DNA. The binding is limited to a relatively short DNA segment, probably no longer than 90 base pairs (bp). Chloroplast and mitochondrial DNA do not bind to the protein, but a low level of binding is displayed by DNA from several other eukaryotic species. The L-protein also has the capacity to nick the bound DNA in the presence of ATP. Nicking does not occur in the absence of binding. Using supercoiled plasmids with zygotene DNA inserts as substrates, the nicking has been found to be confined to a small region of the plasmid and to occur in only one of the strands. The L-protein is considered to be one of the principal factors responsible for the irreversible commitment of cells to meiosis at the end of the preleptotene S-phase. It is also proposed that its endonucleolytic activity plays a role in the initiation of synapsis.
一种分子量为73,000道尔顿的蛋白质已从细线前期、细线期和偶线期细胞的核膜中纯化出来。由于它在抑制偶线期DNA序列从细线期开始直到偶线期DNA合成启动期间的复制中所起的作用，它被命名为细线期蛋白（L蛋白）。已发现该蛋白的抑制活性具有高度特异性。体细胞核和小孢子核中的S期复制不受该蛋白影响。似乎只有偶线期DNA序列受到影响。L蛋白特异性结合偶线期DNA。这种结合限于一个相对较短的DNA片段，可能不超过90个碱基对（bp）。叶绿体和线粒体DNA不与该蛋白结合，但来自其他几种真核生物的DNA显示出低水平的结合。L蛋白在ATP存在下也有能力切割结合的DNA。在没有结合的情况下不会发生切割。以带有偶线期DNA插入片段的超螺旋质粒为底物，发现切割仅限于质粒的一个小区域，并且只发生在一条链上。L蛋白被认为是在细线前期S期末细胞不可逆地进入减数分裂的主要因素之一。还提出其核酸内切酶活性在联会起始中起作用。
