Developmental function of Rb family proteins

描述（由申请人提供）：在控制细胞增殖和分化的许多途径中，视网膜母细胞瘤蛋白（Rb）调控网络的基因在肿瘤发生过程中作为突变或解除管制的频繁靶标（如果不是强制性的）脱颖而出。尽管生物化学和组织培养研究表明Rb家族成员参与了广泛的细胞活动，但Rb在体内和正常发育过程中的真正功能尚不清楚。我们的长期目标是在分子水平上了解Rb家族蛋白的细胞和发育功能。为此，我们设计了一种遗传策略，使我们能够识别与秀丽隐杆线虫Rb同源物lin-35协调作用的基因和途径，以控制基本的发育过程。利用该系统，我们已经证明了LIN-35的典型细胞周期功能以及该蛋白在器官形态发生中的新作用。我们还发现了一个通过UBC-18/UbcH7控制器官形态发生的互补途径，UbcH7是一种保守的泛素偶联酶，参与蛋白质降解的靶向。所提出的实验旨在揭示LIN-35与一个或多个平行通路一起作用的潜在机制，调节秀丽隐杆线虫的器官形态发生。

DESCRIPTION (provided by applicant): Among the many pathways controlling cell proliferation and differentiation, genes of the retinoblastoma protein (Rb) regulatory network stand out as frequent if not obligatory targets for mutation or deregulation during tumorigenesis. Although biochemical and tissue culture studies have implicated Rb family members in a wide range of cellular activities, the bona fide functions of Rb in vivo and during normal development are not well understood. Our long-term objective is to understand the cellular, and developmental functions of Rb family proteins at the molecular level. To this end, we have devised a genetic strategy that has allowed us to identify genes and pathways that function coordinately with the C. elegans Rb homolog, lin-35, to control essential developmental processes. Using this system, we have demonstrated canonical cell cycle functions for LIN-35 as well as a novel role for this protein in organ morphogenesis. We have also uncovered a complementary pathway that acts to control organ morphogenesis through UBC-18/UbcH7, a conserved ubiquitin-conjugating enzyme involved in the targeting of proteins for degradation. The proposed experiments are designed to uncover the underlying mechanism by which LIN-35, acting in conjunction with one or more parallel pathways, regulates organ morphogenesis in C. elegans. Our main objectives fall into two categories. One broad aim is to identify additional factors that function cooperatively with LIN-35 and UBC-18 to control organogenesis. These studies will include the cloning and characterization of sir-9, a gene that, like ubc-18, functions redundantly with lin-35 to control organ morphogenesis; the execution of a two-hybrid screen to identify UBC-18-interacting proteins; and a directed RNAi feeding screen using known or putative ubiquitin pathway components. Our second objective is to identify functionally relevant downstream targets for regulation by LIN-35 and UBC-18. These studies will include genetic selections to isolate mutations that suppress the lethality of lin-35; ubc-18 double mutants; microarray analyses to identify the complete spectrum of LIN-35-regulated transcripts; and additional two-hybrid screens using co-factors of UBC-18 identified through earlier two-hybrid or RNAi-feeding screens. The successful completion of these studies will greatly enhance our general understanding of Rb family functions and will provide detailed mechanistic knowledge of this novel role for Rb proteins in morphogenesis.