Regulation of the Transcription Factor UBF by CHP

说明（申请人提供）钙调神经磷酸酶同源蛋白CHP是一种具有多种功能的Ca 2+结合蛋白，包括调节离子交换剂和钙调神经磷酸酶活性以及组成性囊泡转运。我们最近发现CHP定位于核膜，并且CHP的过表达抑制细胞增殖。上游结合因子UBF是RNA聚合酶I（P01 I）转录起始复合物的必需组分，其功能是转录核rDNA基因。因此，UBF是核糖体生物合成和细胞增殖的关键参与者。我们有证据表明CHP和UBF之间的新型体内相互作用是Ca 2+敏感的。该提案将研究CHP和UBF之间的相互作用调节UBF功能的假设，并且包括两个主要目的：1）研究CHP与UBF的调节关联，以及2）确定CHP与UBF相互作用的功能意义。目的1确定是否UBF直接结合CHP，如果是这样，它是否是Ca 2+依赖性的，并调查CHP和UBF在体内的分布。目的2研究CHP的丰度、Ca ~（2+）结合和膜结合是否调控UBF修饰和/或UBF介导的rDNA转录。这些实验的结果将推进我们的知识，CHP和UBF是如何独立调节，以及它们的相互作用如何调节UBF功能。

DESCRIPTION (provided by applicant) Calcineurin homologous protein, CHP, is a Ca2+-binding protein with diverse functions, including regulation of ion exchanger and calcineurin activities and constitutive vesicular transport. We have recently found that CHP is localized to the nuclear envelope and that overexpression of CHP inhibits cell proliferation. Upstream binding factor, UBF, is a necessary component of the transcription initiation complex of RNA polymerase I (P01 I) that functions to transcribe nuclear rDNA genes. Thus UBF is a key player in ribosome biosynthesis and cell proliferation. We have evidence demonstrating a novel in vivo interaction between CHP and UBF that is Ca2+-sensitive. This proposal will investigate the hypothesis that the interaction between CHP and UBF regulates UBF function, and is comprised of two primary Aims: 1) Investigate the regulated association of CHP with UBF, and 2) Determine the functional significance of the interaction of CHP with UBF. Aim 1 determines whether UBF binds directly to CHP and, if so, whether it is Ca2+-dependent, and investigates the regulated distribution of CHP and UBF in vivo. Aim 2 investigates whether the abundance, Ca2+ binding, and membrane association of CHP regulate UBF modifications and/or UBF-mediated rDNA transcription. Results of these experiments will advance our knowledge of how CHP and UBF are independently regulated as well as how their interaction regulates UBF function.