NPR2, YEAST HOMOLOG OF THE HUMAN TUMOR SUPPRESSOR NPRL2, IS A TARGET OF GRR1

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 Npr2，一种可能的“氮渗透酶调节因子”和人类肿瘤的同源物 抑制子NPRL2被发现与SCF(Grr1)的F盒成分Grr1相互作用 (含Grr1)E3泛素连接酶的(Skp1-cullin-F-box)蛋白复合体，质量分数 基于光谱学的多维蛋白质识别技术。Npr2有两种害虫 序列，并已在泛素化蛋白质中被鉴定。像其他Grr1一样 靶点，Npr2是一种磷蛋白。磷酸化的Npr2在grr1Delta突变体中积累， 而Npr2则稳定在蛋白酶体失活的细胞中。磷酸化与不稳定性 依赖于I型酪蛋白激酶(CK1)YCK1和YK2。Npr2的过度表达是 对细胞有害，在grr1Delta突变体中是致命的。NPR2是实现强劲增长所必需的 含有铵或尿素作为氮源但不用于生长的限定培养基 富媒体。Npr2Delta突变体也不能有效地完成减数分裂。加在一起，这些 数据表明，Npr2是SCF(Grr1)E3泛素的磷酸化依赖靶点 在某些氮源下对细胞生长起作用的连接酶。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Npr2, a putative "nitrogen permease regulator" and homolog of the human tumor suppressor NPRL2, was found to interact with Grr1, the F-box component of the SCF(Grr1) (Skp1-cullin-F-box protein complex containing Grr1) E3 ubiquitin ligase, by mass spectrometry-based multidimensional protein identification technology. Npr2 has two PEST sequences and has been previously identified among ubiquitinated proteins. Like other Grr1 targets, Npr2 is a phosphoprotein. Phosphorylated Npr2 accumulates in grr1Delta mutants, and Npr2 is stabilized in cells with inactivated proteasomes. Phosphorylation and instability depend upon the type I casein kinases (CK1) Yck1 and Yck2. Overexpression of Npr2 is detrimental to cells and is lethal in grr1Delta mutants. Npr2 is required for robust growth in defined medium containing ammonium or urea as a nitrogen source but not for growth on rich medium. npr2Delta mutants also fail to efficiently complete meiosis. Together, these data indicate that Npr2 is a phosphorylation-dependent target of the SCF(Grr1) E3 ubiquitin ligase that plays a role in cell growth on some nitrogen sources.