NON-MEDELIAN INHERITANCE OF MACRONUCLEAR TRAITS

这项提议的主要目的是阐明一种 草履虫中罕见的非孟德尔遗传类型。我们 将结合分子生物学和遗传学研究突变细胞系 (D48)含有A型可变表面抗原的完整拷贝 基因存在于微核中，但不存在于大核中。野生型细胞质 允许将这些序列结合到大核中，但在 D48细胞质染色体断裂不正确，A基因 已删除。最近的实验表明，细胞的大核转化 用含有A抗原基因的重组克隆(PSA14SB)引导 对于微核A基因序列的正确处理 下一个大核的形成(K.Aufderheide，个人 通信)。通过将pSA14SB的特定片段微量注射到 D48我们将定义正确的DNA序列 A基因的加工。将进行进一步的实验，以 确定来自这些序列的RNA产物是否对其 功能。来自d48和野生型细胞系的微核DNA将 分离并用于比较微核序列的组织 围绕着染色体断裂部位。 最近分离出了更多的非孟德尔突变体，这些突变体可以影响 B表面抗原基因的表达(J.Preer，Personal 通信)。我们将克隆B基因，并确定是否类似 这些突变涉及分子机制。 我们相信，这项研究将促进对发展的理解 真核生物中受控的DNA重排，并可能揭示新的 核酸加工的几个方面。

The broad aim of this proposal is to elucidate the molecular details of an unusual type of non-Mendelian inheritance in Paramecium tetraurelia. We will combine molecular biology and genetics to study a mutant cell line (d48) that contains a complete copy of the A type variable surface antigen gene in the micronucleus but not in the macronucleus. Wild type cytoplasm allows the incorporation of these sequences into the macronucleus, but in d48 cytoplasm the chromosome is broken incorrectly and the A gene is deleted. Recent experiments have shown that macronuclear transformation of d48 with a recombinant clone containing the A antigen gene (pSA14SB) leads to the correct processing of the micronuclear A gene sequences during the formation of the next macronucleus (K. Aufderheide, personal communication). By microinjecting specific fragments of pSA14SB into the d48 macronucleus we will define the DNA sequences necessary for the correct processing of the A gene. Further experiments will be performed to determine if RNA products from these sequences are important for their function. Micronuclear DNA from the d48 and wild type cell lines will be isolated and used to compare the organization of the micronuclear sequences surrounding the chromosome breakage sites. Additional non-Mendelian mutants have recently been isolated that affect expression of the B surface antigen gene (J. Preer, personal communication). We will clone the B gene and determine if similar molecular mechanisms are involved in these mutations. We believe this research will advance the understanding of developmentally controlled DNA rearrangements in eukaryotes, and perhaps reveal novel aspects of nucleic acid processing.