Peidis Philippos, Giannakouros Thomas, Burow Matthew E, Williams Robert W, Scott Robert E
Laboratory of Biochemistry, Department of Chemistry, The Aristotle University, 54124 Thessaloniki, Greece.
BMC Syst Biol. 2010 Feb 25;4:14. doi: 10.1186/1752-0509-4-14.
The 250 kDa P2P-R protein (also known as PACT and Rbbp6) was cloned over a decade ago and was found to bind both the p53 and Rb1 tumor suppressor proteins. In addition, P2P-R has been associated with multiple biological functions, such as mitosis, mRNA processing, translation and ubiquitination. In the current studies, the online GeneNetwork system was employed to further probe P2P-R biological functions. Molecular studies were then performed to confirm the GeneNetwork evaluations.
GeneNetwork and associated gene ontology links were used to investigate the coexpression of P2P-R with distinct functional sets of genes in an adipocyte genetic reference panel of HXB/BXH recombinant strains of rats and an eye genetic reference panel of BXD recombinant inbred strains of mice. The results establish that biological networks of 75 and 135 transcription-associated gene products that include P2P-R are co-expressed in a genetically-defined manner in rat adipocytes and in the mouse eye, respectively. Of this large set of transcription-associated genes, >10% are associated with hormone-mediated transcription. Since it has been previously reported that P2P-R can bind the SRC-1 transcription co-regulatory factor (steroid receptor co-activator 1, [Ncoa1]), the possible effects of P2P-R on estrogen-induced transcription were evaluated. Estrogen-induced transcription was repressed 50-70% by the transient transfection of P2P-R plasmid constructs into four different cell types. In addition, knockdown of P2P-R expression using an antisense oligonucleotide increased estrogen-mediated transcription. Co-immunoprecipitation assays confirmed that P2P-R interacts with SRC-1 and also demonstrated that P2P-R interacts with estrogen receptor alpha.
The findings presented in this study provide strong support for the value of systems genetics, especially GeneNetwork, in discovering new functions of genes that can be confirmed by molecular analysis. More specifically, these data provide evidence that the expression of P2P-R co-varies in a genetically-defined manner with large transcription networks and that P2P-R can function as a co-repressor of estrogen-dependent transcription.
250 kDa的P2P-R蛋白（也称为PACT和Rbbp6）在十多年前被克隆出来，发现它能与p53和Rb1肿瘤抑制蛋白结合。此外，P2P-R与多种生物学功能相关，如细胞有丝分裂、mRNA加工、翻译和泛素化。在当前研究中，利用在线基因网络系统进一步探究P2P-R的生物学功能。随后进行分子研究以证实基因网络评估结果。
在大鼠HXB/BXH重组品系的脂肪细胞遗传参考面板和小鼠BXD重组近交系的眼睛遗传参考面板中，利用基因网络及相关基因本体链接来研究P2P-R与不同功能基因集的共表达情况。结果表明，分别在大鼠脂肪细胞和小鼠眼睛中，包含P2P-R的75个和135个与转录相关的基因产物的生物网络以基因定义的方式共表达。在这一大组与转录相关的基因中，超过10%与激素介导的转录相关。由于此前有报道称P2P-R能结合SRC-1转录共调节因子（类固醇受体共激活因子1，[Ncoa1]），因此评估了P2P-R对雌激素诱导转录的可能影响。将P2P-R质粒构建体瞬时转染到四种不同细胞类型中，雌激素诱导的转录被抑制了50 - 70%。此外，使用反义寡核苷酸敲低P2P-R表达可增加雌激素介导的转录。免疫共沉淀分析证实P2P-R与SRC-1相互作用，还表明P2P-R与雌激素受体α相互作用。
本研究结果为系统遗传学（尤其是基因网络）在发现可通过分子分析证实的基因新功能方面的价值提供了有力支持。更具体地说，这些数据提供了证据，表明P2P-R的表达以基因定义的方式与大型转录网络共同变化，并且P2P-R可作为雌激素依赖性转录的共抑制因子发挥作用。
