MAMMALIAN SPERMATOGENESIS--HISTONES/DNA REORGANIZATION

哺乳动物精子发生的特点是进行性的 当鱼精蛋白取代组蛋白时，染色质发生缩合 DNA一种新的小鼠H_2B基因的转录和翻译 特别是在减数分裂后圆形精子细胞中编码一种蛋白质 它含有一个极其疏水的羧基末端， 这表明它可能与核膜相互作用。这个 该方案中的实验旨在检验：1) 在限制转录和转录中起重要作用的信号 将这一基因翻译到特定的生精人群， 即圆形精子细胞；以及，2)该蛋白可能具有的作用 在染色质重组中。精子细胞特异性分析 H_2B基因可能识别在细胞周期中起关键作用的序列元件 限制其表达。与大多数其他组蛋白mRNAs不同，这 转录本是多聚腺苷化的。因为精子发生的时间超过两个月 在小鼠的周期期，多聚腺苷酸化可能在 稳定这些成绩单将通过生成 用含有该基因的载体转化体细胞系 带有和不带有其多聚腺苷基化信号序列。一种抗血清 对唯一的羧基末端区域进行识别 这种蛋白质。尤其是它在单倍体中的定位 核及其在精子发生过程中的命运将被研究。 该蛋白质在染色质组织中的功能将是 通过在转化的细胞系中产生它和它的 转基因小鼠的过度生产。 由于核异常经常在猪的精子中观察到 基因不育的小鼠，缺乏特定基因的表达 可能会阻碍正常的染色质凝聚和随后的精子 发展。染色质的重组可能允许 精子发生过程中特定DNA序列的定位。这 区隔对转录可能是很重要的 精子发生后期和早期的调控 胚胎发育。

Mammalian spermatogenesis is characterized by the progressive condensation of chromatin as protamines replace histones on the DNA. A novel mouse H2b gene which is transcribed and translated specifically in post-meiotic round spermatids codes for a protein which contains an extremely hydrophobic carboxyl-terminus, suggesting that it may interact with the nuclear membrane. The experiments in this proposal are designed to examine: 1) the signals that are important in restricting the transcription and translation of this gene to a particular spermatogenic population, i.e., round spermatids; and, 2) the possible role this protein has in chromatin reorganization. Analysis of the spermatid-specific H2b gene may identify sequence elements that are critical in restricting its expression. Unlike most other histone mRNAs, this transcript is polyadenylated. As spermiogenesis occurs over a two week period in the mouse, the possible role of polyadenylation in stabilizing these transcripts will be examined by generating transformed somatic cell lines with constructs containing the gene with and without its polyadenylation signal sequence. An antiserum raised against the unique carboxyl-terminal region will identify this protein. In particular, its localization within the haploid nucleus and its fate as spermiogenesis proceeds will be examined. The function of the protein in chromatin organization will be assessed by its production in transformed cell lines and its overproduction in transgenic mice. As nuclear abnormalities frequently are observed in sperm of genetically sterile mice, the lack of expression of specific genes may hinder normal chromatin condensation and subsequent sperm development. Reorganization of the chromatin may permit localization of specific DNA sequences during spermiogenesis. This compartmentalization may be important for transcriptional regulation both late in spermatogenesis and in the early stages of embryonic development.