Formation and biological functions of unusual DNA/RNA structures formed by repeat sequences.

超过50%的基因组是串联重复的DNA序列，包括端粒、着丝粒、大卫星、小卫星和微卫星重复。重复DNA可以存在于典型的右手B型双螺旋之外的不寻常的结构中。重复序列在基因和染色体中的特定位置突出了它们在生物学上的重要性，特别是关于它们形成的不寻常的结构。有证据表明，重复结构在基因调控、剪接、重组、表观遗传调控、重复长度突变等方面发挥作用，其功能可能通过重复形成的生物物理结构来反映。重要的是，重复束的长度极易发生变化，这些长度的变化会极大地影响它们的生物学功能。长度的变化可能涉及到不寻常的结构。我们的目标是了解不寻常的重复结构及其如何改变长度。*在DNA复制、修复、重组和转录过程中，当互补链变得不成对和单链时，可能会形成不寻常的重复结构。重复序列的寄存器外未对齐形成滑动DNA。新转录的RNA可以形成不寻常的结构，如链内发夹和G-四链。一些DNA序列可以形成转录诱导的RNA：称为R-环的DNA杂交体。这些序列在基因和染色体中的特定位置突出了它们的生物学重要性，特别是在它们形成的替代结构方面，这些结构极有可能具有功能作用。人们对这些功能知之甚少。大多数结构分析都是在没有伴侣链的情况下对分离的DNA链进行的。此外，大多数研究使用短的合成寡核苷酸重复序列，比它们的生物对应序列短得多，后者在两条互补链存在的情况下发生。这类研究得出的结果可能只部分反映了生物学上可能发生的事情。彻底了解由这些重复序列形成的结构，即相互作用和处理它们的蛋白质，必须包括使用与生物相关的互补链长度的研究。*重点放在与疾病有关和不与疾病相关的广泛重复序列(端粒、着丝粒、大、小和微卫星重复序列)上，我们将研究重复序列形成异常结构的过程；评估蛋白质-核酸相互作用，以及某些蛋白质在处理这些异常结构以处理重复长度变化中的作用。这项建议侧重于重复序列的基本分子和生物学方面。这项提议的结果将阐明其中一些重复的自然和与疾病有关的方面。在这里研究的重复序列的子集上的疾病相关研究是其他资助的重点。

More than 50% of most genomes are tandem repetitive DNA sequences, including telomeres, centromeres, macro-, mini- and microsatellite repeats. Repeat DNAs can exist in unusual structures beyond the canonical right-handed B-form double helix. The specific locations of repeats in genes and chromosomes highlight their biological importance, particularly with respect to the unusual structures they form. Evidence indicates that repeat structures play roles in gene regulation, splicing, recombination, epigenetic regulation, repeat length mutation, etc. Functions are likely to be reflected by the biophysical structures formed by the repeats. Importantly, the length of the repeat tracts are hyper-prone to change and these length changes can dramatically affect their biological function. Length changes likely involve unusual structures. Our goal is to understand unusual repeat structures and how they can change lengths.******The formation of unusual repeat structures likely occurs during DNA replication, repair, recombination and transcription, when complementary strands become unpaired and single-stranded. Slipped-DNAs form by out-of-register misalignment of repeats. Newly transcribed RNAs can form unusual structures such as intra-strand hairpins and G-quadruplexes. Some DNA sequences can form transcriptionally induced RNA:DNA hybrids called R-loops. The specific locations of these sequences in genes and chromosomes highlight their biological importance, particularly with respect to the alternative structures they form, which are highly likely to have functional roles. These functions are poorly understood. Most structural analyses are performed on isolated DNA strands in the absence of their partner strand. Furthermore, most studies use short synthetic oligo repeats that are dramatically shorter than their biological counter-parts, which occur in the presence of both complementary strands. Such studies yield results that may only partially reflect what may occur biologically. A thorough understanding of the structures formed by these repeats, the proteins that interact and process them, must include studies using biologically relevant lengths of the complementary strands.******With a focus upon a broad range of repeats (telomeres, centromeres, macro-, mini-, and micro-satellite repeats), that are and are not associated with disease, we will study the formation of unusual structures by the repeats; assess protein-nucleic acid interactions, as well as the roles of certain proteins in processing these unusual structures to repeat length changes. This proposal focuses upon the basic fundamental molecular and biological aspects of repeat sequences. The results of this proposal will shed light upon both the natural and disease related aspects of some of these repeats. Disease-related studies on a subset of the repeats studied herein are the focus of other grants.