Department of Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel.
PLoS Genet. 2010 Aug 12;6(8):e1001063. doi: 10.1371/journal.pgen.1001063.
It is increasingly clear that transcription factors play versatile roles in turning genes "on" or "off" depending on cellular context via the various transcription complexes they form. This poses a major challenge in unraveling combinatorial transcription complex codes. Here we use the powerful genetics of Drosophila combined with microarray and bioinformatics analyses to tackle this challenge. The nuclear adaptor CHIP/LDB is a major developmental regulator capable of forming tissue-specific transcription complexes with various types of transcription factors and cofactors, making it a valuable model to study the intricacies of gene regulation. To date only few CHIP/LDB complexes target genes have been identified, and possible tissue-dependent crosstalk between these complexes has not been rigorously explored. SSDP proteins protect CHIP/LDB complexes from proteasome dependent degradation and are rate-limiting cofactors for these complexes. By using mutations in SSDP, we identified 189 down-stream targets of CHIP/LDB and show that these genes are enriched for the binding sites of APTEROUS (AP) and PANNIER (PNR), two well studied transcription factors associated with CHIP/LDB complexes. We performed extensive genetic screens and identified target genes that genetically interact with components of CHIP/LDB complexes in directing the development of the wings (28 genes) and thoracic bristles (23 genes). Moreover, by in vivo RNAi silencing we uncovered novel roles for two of the target genes, xbp1 and Gs-alpha, in early development of these structures. Taken together, our results suggest that loss of SSDP disrupts the normal balance between the CHIP-AP and the CHIP-PNR transcription complexes, resulting in down-regulation of CHIP-AP target genes and the concomitant up-regulation of CHIP-PNR target genes. Understanding the combinatorial nature of transcription complexes as presented here is crucial to the study of transcription regulation of gene batteries required for development.
越来越明显的是，转录因子通过它们形成的各种转录复合物，根据细胞环境的不同，在基因的“开启”或“关闭”中发挥着多样的作用。这给解开组合转录复合物密码带来了重大挑战。在这里，我们利用果蝇强大的遗传学特性，结合微阵列和生物信息学分析来应对这一挑战。核衔接蛋白 CHIP/LDB 是一种主要的发育调节剂，能够与各种类型的转录因子和辅助因子形成组织特异性转录复合物，使其成为研究基因调控复杂性的有价值模型。迄今为止，只有少数 CHIP/LDB 复合物的靶基因被鉴定出来，而且这些复合物之间可能存在依赖组织的串扰，尚未得到严格探索。SSDP 蛋白保护 CHIP/LDB 复合物免受蛋白酶体依赖性降解，是这些复合物的限速辅助因子。通过使用 SSDP 突变，我们鉴定了 189 个 CHIP/LDB 的下游靶基因，并表明这些基因富含 APTEROUS（AP）和 PANNIER（PNR）的结合位点，AP 和 PNR 是与 CHIP/LDB 复合物相关的两个经过充分研究的转录因子。我们进行了广泛的遗传筛选，并鉴定了与 CHIP/LDB 复合物成分在指导翅膀（28 个基因）和胸部刚毛（23 个基因）发育方面具有遗传相互作用的靶基因。此外，通过体内 RNAi 沉默，我们揭示了两个靶基因 xbp1 和 Gs-alpha 在这些结构早期发育中的新作用。总之，我们的结果表明，SSDP 的缺失破坏了 CHIP-AP 和 CHIP-PNR 转录复合物之间的正常平衡，导致 CHIP-AP 靶基因下调和 CHIP-PNR 靶基因上调。如本文所述，理解转录复合物的组合性质对于研究发育所需的基因电池的转录调控至关重要。
