Differential changes in copy numbers of rice mitochondrial plasmid-like DNAs and main mitochondrial genomic DNAs that depend on temperature

The mitochondria of rice contain four kinds of circular plasmid-like DNAs, namely, B1, B2, B3 and B4, in addition to the main mitochondrial genomic DNAs. In order to examine the genetic stability of mitochondrial plasmid-like DNAs, changes in the amounts of plasmid-like DNAs and main mitochondrial genomic DNAs were analyzed in calli that had been cultured at various temperatures. The observed effect of temperature on the levels of plasmid-like DNAs was larger than that on the main mitochondrial genomic DNAs. A significant reduction in the copy number of plasmid-like DNAs was detected in calli cultured at 35 °C, as compared to 20 °C, 25 °C and 30 °C. The effect of temperature on DNA synthesis in isolated mitochondria was also analyzed. Synthesis of the main mitochondrial genomic DNAs occurred at all the temperatures examined, whereas synthesis of plasmid-like DNAs occurred only over a limited range of temperatures. The results of both in vivo and in vitro analyses suggest that plasmid-like DNAs are less stably maintained than the main mitochondrial genomic DNAs, which is consistent with the notion that the transmission of mitochondrial plasmid-like DNAs from one generation to the next may be unstable under unusual conditions. Received: 17 February 1997 / 24 April 1998     

A ribosomal protein gene cluster is encoded in the mitochondrial DNA of Dictyostelium discoideum: UGA termination codons and similarity of gene order to Acanthamoeba castellanii

We sequenced a region of about 14.5 kb downstream from the ribosomal protein L11 gene (rpl11) in the mitochondrial DNA (54±2 kb) of the cellular slime mold Dictyostelium discoideum. Sequence analysis revealed that eleven ribosomal protein genes and six open reading frames (ORFs) formed a cluster arranged in the order: rpl11–orf189–rps12–rps7–rpl2–rps19–orf425–orf1740–rpl16–rpl14–orf188–rps14–rps8–rpl6–rps13–orf127–orf796. This order was very similar to that of homologous genes in Acanthamoeba castellanii mitochondrial DNA. The N-terminal region of ORF425 and the C-terminal region of ORF1740 had partial similarities to the S3 ribosomal protein of other organisms. The termination codons of rpl16 and orf188 were UGA, which has not hitherto been found in genes encoded in D. discoideum mitochondrial DNA. Received: 28 August 1997 / 2 January 1998     

Xq25 duplication: the crucial role of the STAG2 gene in this novel human cohesinopathy

The Xq25 duplications syndrome has recently emerged as a distinct clinical entity. We report here on six new patients belonging to two unrelated families and harbouring an Xq25 microduplication detected by array CGH. Similarly to previously reported cases, the phenotype of our patients is characterized by delayed milestones, speech disturbance, intellectual disability, abnormal behaviours and a characteristic facial dysmorphism. The common duplicated interval allowed further refinement of the shortest region of overlap to 173 kb, including only one gene, STAG2, which encodes a component of the cohesin complex. We suggest that increased STAG2 gene copy number and dysregulation of its downstream target genes may be responsible for the specific clinical findings of this syndrome. Therefore, the Xq25 microduplication could be considered as a novel cohesinopathy, thus increasing the group of these disorders.     

Physical and gene mapping of cauliflower (Brassica oleracea) mitochondrial DNA

Summary A physical map of the mitochondrial DNA isolated from B. oleracea (cauliflower) inflorescences was constructed with the restriction endonucleases Sall, Kpnl and Bgll. Physical mapping was made using the multi enzyme method with either unlabeled or labeled DNA fragments isolated by preparative electrophoresis and a clone bank prepared by inserting incomplete Sall restriction digests of mitochondrial DNA into a cosmid vector.The different mapping studies led to a circular map, about 217 kb in size, containing the entire sequence complexity of the genome. The 26S and 18S – 5S ribosomal RNA genes appeared to be separated by about 75 kb in this map. However, the particular cross-hybridization between several restriction fragments and the sequential diversity of some cosmids indicated that intra molecular recombination may occur naturally in higher plant mitochondria. Namely, one recombinational event resulted in the ribosomal RNA genes mapping closer together.Abbreviations mtDNA mitochondrial DNA - kb kilobasepairs - rRNA ribosomal RNA - LGT agarose low gelling temperature agarose     

一个线粒体DNA耗竭综合征家系临床及DGUOK基因分析

目的对一个线粒体DNA耗竭综合征家系进行遗传基因变异分析,探讨其分子发病机制。方法提取家系中患者及其父母外周血基因组DNA,采用高通量测序技术检测致病基因变异,并对变异进行Sanger测序验证。结果发现患者DGUOK基因存在c.505_508delTATC的纯合变异,父母都是该位点的杂合变异携带者。c.505_508delTATC为未见报道的新变异位点,造成169位氨基酸由酪氨酸(Y)变异为精氨酸(R),随后编码框改变,在199位翻译提前终止,理论上产生截短蛋白p.Y169Rfs31X。结论c.505_508delTATC为DGUOK基因致病性变异,扩展了DGUOK基因变异谱。     

AP1反应元件的确定及在细胞角蛋白13基因表达调控中的作用

目的 确定细胞角蛋白13（cytokeratin 13,CK13)基因5'旁侧－nt，199－－nt.192碱基CTGAATCA反应元件的类型及其在CK13基因表达调控中的作用。方法 采用报告基因分析的,构建CK13基因5'旁侧513bp全片段，－nt.207- nt.63与氯霉素乙酰转移酶报告基因增强子载体的重组体，并采用PCR定点诱变技术，构建与－nt.207 nt.63同样长短，但-nt.197和T、G分别定点诱变为A，T的氯霉素乙酰转移酶报告基因增强子载体的重组体，通过脂质体介导的转染技术导入HeLa细胞，检测各重组体报告基因的瞬间表达，确定CK13基因5'旁侧－nt.199--nt.192碱基CTGAATCA在CK13基因表达调控中的作用；并采用凝胶滞留试验及竞争性凝胶滞留试验验证CK13基因5'旁侧中CTGAATCA反应元件的类型。结果 凝胶滞留试验及竞争性凝胶滞留试验证实CK13基因5'旁侧中CTGAATCA反应元件的类型。结果 凝胶滞留试验及竞争性凝胶滞留试验证实CK13基因5'旁侧－nt.199--nt.192碱基CTGAATCA反应元件是AP1反应元件，它促进CK13基因的表达。结论 CK13基因5'旁侧起始密码上游－nt.199--nt.192的碱基CTGAATCA是AP1反应元件，而不是cAMP反应元件，它可增强CK13基因5'旁侧的转录活性。     

Intragenic rearrangements in the mitochondrial NADH dehydrogenase subunit 6 gene of vertebrates

We have sequenced the mitochondrial-encoded NADH dehydrogenase subunit 6 gene from 19 species of birds. Comparison of the derived amino-acid sequences in 22 avian species, six mammals, and two fishes, reveals an intragenic rearrangement in mammals. The C-terminal half of the mammalian protein includes an internal insertion of 10–15 amino acids and a C-terminal deletion of 8–9 amino acids. Based on comparative sequence alignments and hydropathy profile analysis, five hydrophobic segments (designated I to V) corresponding to transmembrane regions are proposed. In this structural model of NADH dehydrogenase subunit 6, the mammalian insertion is found in a variable loop region between transmembrane segments IV and V.     

人淋巴细胞抑制素基因克隆与表达的研究

目的：获人SPN基因,构建SPN的原核表达载体。方法：采用RT－PCR的方法从激活的人外周血淋巴细胞的总cDNA中得到1493bp的人SPN基因,NdeI,BamH I双酶切后定向克隆到原核表达载体pET-11-c中,全自动测序仪测序,转化宿主菌BL21后,IPTG诱导,SDS－PAGE电泳分析。结果：成功克隆到人SPN基因,并构建表达质粒,SDS－PAGE电泳证实目的蛋白表达。结论：为进一步研究SPN的免疫抑制机理和作用以及探讨SPN作为新型生理性免疫抑制剂的可能性打下了坚实的基础。     

Nuclear suppressors of mitochondrial chloramphenicol resistance in Baker's yeast: their use for the isolation of novel mutants

Summary Strains that are genotypically sensitive to chloramphenicol and also contain one of the nuclear suppressors of mitochondrial chloramphenicol resistance (Waxman et al. 1979) were constructed. A manganese mutagenesis on such a strain produced chloramphenicol resistant mutants, most of which resulted from mutations in nuclear genes. These mutants may be either dominant or recessive, and they probably do not code for membrane proteins. The few mitochondrial mutants fall into several classes, but all result from mutations in the 21S rRNA gene. The suppressor allele effectively prevents the appearance of the most common group of mitochondrial mutants (those that map at cap1), and thereby enhances the selection of novel mutants in the region.