Establishment of the meiotic cell cycle program through post-transcriptional regulation by MEIOC and YTHDC2

项目概要/摘要 二倍体生殖细胞通过减数分裂的还原分裂转化为单倍体配子。减数分裂后 DNA合成，生殖细胞进入减数分裂前期I，它与有丝分裂前期有两个区别。 主要特点。第一，减数分裂前期I明显长于有丝分裂前期。二、减数分裂 前期I涉及一系列复杂的染色体事件，这些事件有助于建立 单倍体状态前期I的延长长度对于这些染色体事件的完成至关重要， 从前期I过早退出导致重组缺陷和染色体错误分离。在哺乳动物中， 减数分裂前期I被Meioc和Ythdc 2延长。在男性和女性都没有任何一种基因的情况下， 减数分裂生殖细胞不能完成减数分裂前期I，并过早地进入异常的中期， 最后，放弃。一些初步的观察表明，MEIOC和YTHDC 2的功能是作为一个 复杂的转录后调节减数分裂生殖细胞内的细胞周期因子。MEIOC和YTHDC 2是 首先在减数分裂开始时在生殖系中表达，它们彼此相互作用，以及与一个 重叠的转录本，包括关键的细胞周期调节因子。这些目标富含RNA 修饰N6-甲基腺苷（m6 A），其优先被YTHDC 2的YTH结构域识别， 其用于靶向和转录后调节RNA。在没有Meioc、MEIOC和 YTHDC 2的目标表现出降低的稳定性。转录物稳定性的变化通常伴随着 在HeLa细胞中，YTHDC 2增强了翻译效率，同时降低了mRNA水平。 丰饶。然而，MEIOC和YTHDC 2是否影响减数分裂生殖中的翻译仍然是未知的 细胞该提议将检验MEIOC和YTHDC 2作为复合物来识别和 为了建立减数分裂特异性细胞周期程序，预先调节m6 A修饰的mRNA。这 将通过三个具体目标来检验假设。第一个目标将评估MEIOC影响YTHDC 2的能力。 与RNA的相互作用，特别是细胞周期相关的转录本，通过鉴定YTHDC 2 在存在和不存在Meioc的情况下结合。此外，m6 A是否有助于MEIOC和YTHDC 2的 还将评估与RNA相互作用的能力。第二个目标将确定翻译的变化， 发生在生殖细胞从有丝分裂到减数分裂的转变时，以及在野生型和无Meioc样品之间。在 特别是，这一目标将确定细胞周期因子是否在减数分裂开始时受到抑制 以及通过Meioc的上调。第三个目标将决定MEIOC和YTHDC 2是否连续 需要在减数分裂前期I，以防止早熟细胞周期的进展，以及确定 这一假定要求背后的机械监管。总的来说，这些关于MEIOC的基础研究 而YTHDC 2对减数分裂前期I长度的调节将为建立一个新的基因组提供关键的见解。 以及减数分裂细胞周期程序的调节，对生育、发育和癌症具有更广泛的意义。

PROJECT SUMMARY/ABSTRACT Diploid germ cells are transformed into haploid gametes via the reductive division of meiosis. After meiotic DNA synthesis, germ cells enter meiotic prophase I, which distinguishes itself from mitotic prophase by two major characteristics. First, meiotic prophase I is dramatically longer than mitotic prophase. Second, meiotic prophase I involves an intricate series of chromosomal events that contribute to the establishment of the haploid state. The extended length of prophase I is critical for the completion of these chromosomal events, as premature exit from prophase I causes recombination defects and chromosome mis-segregation. In mammals, meiotic prophase I is prolonged by Meioc and Ythdc2. In the absence of either gene in both males and females, meiotic germ cells fail to complete meiotic prophase I and prematurely enter an abnormal metaphase before ultimately apoptosing. Several preliminary observations suggest that MEIOC and YTHDC2 function as a complex to post-transcriptionally regulate cell cycle factors within meiotic germ cells. MEIOC and YTHDC2 are first expressed in the germ line at meiotic initiation, and they interact with one another as well as with an overlapping set of transcripts, including key cell cycle regulators. These targets are enriched for the RNA modification N6-methyladenosine (m6A), which is preferentially recognized by YTHDC2's YTH domain and which is used to target and post-transcriptionally regulate RNA. In the absence of Meioc, MEIOC and YTHDC2's targets exhibit reduced stability. Changes in transcript stability are oftentimes accompanied by changes in translation, and in HeLa cells, YTHDC2 enhances translational efficiency while decreasing mRNA abundance. However, it remains unknown whether MEIOC and YTHDC2 affect translation in meiotic germ cells. This proposal will test the hypothesis that MEIOC and YTHDC2 function as a complex to recognize and translationally regulate m6A-modified mRNA in order to establish a meiosis-specific cell cycle program. This hypothesis will be tested via three specific aims. The first aim will assess MEIOC's ability to affect YTHDC2's interactions with RNA, particularly cell cycle-related transcripts, by identifying the transcripts that YTHDC2 binds to in the presence and absence of Meioc. In addition, whether m6A contributes to MEIOC and YTHDC2's ability to interact with RNA will also be assessed. The second aim will identify the translational changes that occur as germ cells transition from mitosis to meiosis, as well as between wild-type and Meioc-null samples. In particular, this aim will determine whether cell cycle factors are translationally repressed at the onset of meiosis and by the upregulation of Meioc. The third aim will determine whether MEIOC and YTHDC2 are continuously required during meiotic prophase I to prevent precocious cell cycle progression, as well as identify the mechanistic regulation behind this putative requirement. Collectively, these fundamental studies on MEIOC and YTHDC2's regulation of the length of meiotic prophase I will provide key insights into the establishment and regulation of the meiotic cell cycle program, with broader implications for fertility, development, and cancer.