PROTEIN/RNA INTERACTIONS IN SPLICE SITE SELECTION

描述（由申请人提供）：大多数人类基因被称为内含子的非编码序列打断。新生转录本必须经过处理以去除内含子并将编码序列连接到相邻的成熟mRNA分子中。人类基因组计划提供了一个估计，在大约3x10/9碱基对（bp）的基因组中，编码序列或外显子仅占1 - 1.5%，而内含子约占基因组的24%。很明显，细胞机制面临着一项艰巨的任务，即在基因转录物中精确定位剪接位点。当某些外显子序列被跳过或包含时，复杂性的另一个维度就增加了，这种现象被称为选择性剪接。选择性剪接存在于大量的人类基因中，在发育和分化过程中对基因的表达起着重要的调节作用。选择性剪接还负责在某些细胞（如神经元）中产生分子多样性。

DESCRIPTION (provided by applicant): Most human genes are interrupted by non-coding sequences known as introns. The nascent transcript must be processed to remove the introns and to join the coding sequence into a contiguous mature mRNA molecule. The human genome project provided an estimate that only 1 to 1.5% of the approximately 3x10/9 base pair (bp) genome is spanned by coding sequences or exons, whereas introns occupy approximately 24% of the genome. It is apparent that the cellular machinery is presented with a formidable task to precisely locate the splice sites within a gene's transcript. Another dimension of complexity is added when certain exon sequences are skipped or included, a phenomenon known as alternative splicing. Alternative splicing occurs in a large number of human genes and it plays important roles in regulating gene expression during development and differentiation. Alternative splicing is also responsible for generating molecular diversity in certain cells, such as neurons. Splicing of pre-mRNA involves an ordered assembly of components, including small nuclear ribonucleoprotein particles (snRNP) and additional protein splicing factors, resulting in the formation of a large 50-60S complex, termed the spliceosome. We are interested in understanding the molecular mechanism of splice site recognition from a structural standpoint. In this proposal, we focus our study on several well characterized human splicing factors that are important for splice site selection, namely, SR proteins, heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) and the U2 auxiliary factor (U2AF).