POU同源域蛋白的结构及发育中的功能

POU同源域蛋白含有两个保守的亚结构域以及它们之间有变化的连接区.两个亚结构域与DNA相互作用,在连接区可塑性和辅因子的帮助下,POU蛋白作为调控因子和转录因子,显示出错综复杂的DNA结合和识别能力.在脊椎动物和无脊椎动物中,POU蛋白参与胚胎发生的早期过程,在细胞谱系的分化和神经发育中起调控作用.     

猪POU1F1基因5’侧翼区克隆及序列分析

POU1F1基因是POU基因家族的成员之一,对哺乳动物的早期发育和相关基因启动表达起重要的调控作用。本文利用染色体步移技术,从长白猪基因组中首次克隆到了约1．5kb的POU1F1基因5’侧翼区序列,并利用相关软件对其进行了序列分析和物种间POU1F1基因5’侧翼区序列比对及进化树构建。结果表明所克隆的片段中含典型的TATA盒（-57）和类CAAT盒序列（-87）。TESS软件分析发现在启动子附近有一系列潜在的重要的转录因子结合位点。序列比对结果表明不同物种POU1F1基因的转录起始点上游-150bp区域保守性较强,可能是启动子的核心序列。其中猪与牛的同源性最高,其次是黑猩猩、人、狗,与大鼠、小鼠和鸡同源性较低,与斑马鱼序列同源性最低。同源序列主要集中在转录起始点上游-150bp至-1000bp区域。Vista中的MLAGAN程序构建的系统进化树真实反应了物种间进化关系。     

Identification of two novel mutations in POU4F3 gene associated with autosomal dominant hearing loss in Chinese families

Autosomal dominant non‐syndromic hearing loss is genetically heterogeneous with 47 genes identified to date, including POU4F3. In this study, by using a next‐generation sequencing panel targeting 127 deafness genes, we identified a pathogenic frameshift mutation c.704_705del and a missense mutation c.593G>A in two three‐generation Chinese families with late‐onset progressive ADNSHL, respectively. The novel mutations of POU4F3 co‐segregated with the deafness phenotype in these two families. c.704_705del caused a frameshift p.T235fs and c.593G>A caused an amino acid substitution of p.R198H. Both mutations led to an abnormal and incomplete protein structure. POU4F3 with either of the two mutations was transiently transfected into HEI‐OC1 and HEK 293 cell lines and immunofluorescence assay was performed to investigate the subcellular localization of mutated protein. The results indicated that both c.704_705del (p.T235fs) and c.593G>A (p.R198H) could impair the nuclear localization function of POU4F3. The p.R198H POU4F3 protein was detected as a weak band of the correct molecular weight, indicating that the stability of p.R198H POU4F3 differed from that of the wild‐type protein. While, the p.T235fs POU4F3 protein was expressed with a smaller molecular weight, implying this mutation result in a frameshift and premature termination of the POU4F3 protein. In summary, we report two novel mutations of POU4F3 associated with progressive ADNSHL and explored their effects on POU4F3 nuclear localization. These findings expanded the mutation spectrum of POU4F3 and provided new knowledge for the pathogenesis of POU4F3 in hearing loss.     

Characteristic patterns of N Oct-3 binding to a set of neuronal promoters

N Oct-3, a neurospecific POU protein, homodimerizes in a non-cooperative fashion on the neuronal aromatic l-amino acid decarboxylase gene promoter and generates heterodimers with HNF-3beta. Several other neuronal gene promoters, the corticotropin releasing hormone and the aldolase C gene promoters also contain overlapping binding sites for N Oct-3 and HNF-3beta. We have demonstrated that N Oct-3 presents a non-cooperative homodimerization on these two additional targets and can also give rise to heterodimers with HNF-3beta. Surprisingly, despite the high degree of conservation of the respective POU subunits, the ubiquitous POU protein Oct-1 can only form monomers even in the presence of either N Oct-3 or HNF-3beta on these DNA targets. Our data indicate that this difference is correlated with the specific ability of a portion of the N Oct-3 linker to fold as an alpha-helix, a property shared by class III POU proteins. These results suggest that this novel binding pattern permits the heterodimerization of N Oct-3 and HNF-3beta on the neuronal promoters, which could be a key issue in the development of the nervous system and possibly tumors of neural origin.