Escherichia coli protein StpA stimulates self-splicing by promoting RNA assembly in vitro.

An Escherichia coli gene, stpA, has been identified and cloned based on its ability to suppress the Td- phenotype of a resident, splicing-defective phage T4 td (thymidylate synthase) gene. The stpA gene, which was localized to 60.24 min on the E. coli chromosome, encodes a 15.3-kDa protein. Overproduction of StpA in vivo led to an increase in td pre-mRNA levels and modest enhancement of td mRNA:pre-mRNA ratios. Consistent with its in vivo effect, purified StpA promoted RNA splicing in vitro, and facilitated RNA annealing and strand exchange with model substrates. These results suggest that StpA promotes splicing of the intron by binding RNA nonspecifically, resolving misfolded precursor molecules and facilitating association of critical base pair elements. Furthermore, proteinase K treatment of StpA-assembled precursors prior to the initiation of the splicing reaction still resulted in splicing enhancement, indicating that StpA is not required for the catalytic step, unlike the Neurospora splicing effector CYT-18, whose presence was necessary for catalysis to proceed. Together these results suggest that StpA has chaperone activity in vitro, with the property of promoting assembly of the precursors into an active conformation, in contrast to splicing effectors that stabilize the catalytically active intron structure.     

Studies on homoveratric acid transformation by the ligninolytic fungus Pleurotus eryngii

Homoveratric acid (HVA) degradation was observed in cultures of Pleurotus eryngii lacking lignin peroxidase (LiP) activity. Extracellular enzymes seemed responsible for this transformation, and the lack of activity after ultrafiltration of the culture liquid suggests that the presence of some low-molecular-size compounds is required. This hypothesis is supported by rapid HVA transformation after addition of the synthetic laccase substrate 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) to the ultrafiltered liquid. HVA transformation by the extracellular enzymes from P. eryngii takes place via C-C breakdown and formation of veratryl alcohol, which is further transformed into veratraldehyde. The same major compounds were found during HVA transformation by LiP from Phanerochaete chrysosporium, but this reaction was not stimulated by ABTS. Although the involvement of other enzymes cannot be ruled out, purified laccase from Pleurotus eryngii caused the same HVA transformation pattern in presence of ABTS. Moreover, veratryl alcohol oxidation by P. eryngii laccase was demonstrated in the presence of ABTS. These results suggest that enzymatic systems lacking LiP could be responsible for natural degradation of lignin.     

铜绿假单胞菌PIC－N萘降解基因的研究

铜绿假单胞菌（Ｐｓｅｕｄｏｍｏｎａｓａｅｒｕｇｉｎｏｓａ）ＰＩＣ－Ｎ对萘、邻苯二甲酸、水杨酸等有较强的氧化能力。发现该菌株以禁为底物可诱导产生芳香烃分解酶系。菌株中存在一个５７．４ｋｂ的质粒,经限制性内切酶ＨｉｎｄⅢ处理可产生７个片段,用限制性内切酶ＥｃｏＲⅠ处理可产生８个片段。将以限制性内切酶ＨｉｎｄⅢ部分酶切的片段克隆至大肠杆菌质粒ｐＭＦＹ４３上,获得２９个克隆株。通过对含有菌株ＰＩＣ－Ｎ质粒ＨｉｎｄⅢ片段的７个重组质粒进行限制酶分析,绘出了该质粒ＨｉｎｄⅢ内切酶７个切点的酶切图谱。     

长吻鮠的卵巢发育和周年变化及繁殖习性研究

本文报道了长吻卵巢发育与周年变化特点和繁殖习性。依外形和组织学特征,性成熟前至性成熟鱼卵巢的发育可分为卵原细胞期、单层滤泡期、卵黄泡期,卵黄充满期、成熟期和退化期６个时期,Ⅰ期性腺只存在于１龄内个体,Ⅱ期性腺持续２年左右,性成熟前发育至Ⅲ期,经Ⅳ、Ⅴ期发育至成熟并首次参与繁殖,最小性成熟个体３龄。性成熟后个体卵巢的发育只有后５个时期。繁殖期４—６月,产后卵巢很快退回到Ⅱ期,Ⅲ期卵巢越冬。一次产卵类型。卵壳膜源于滤泡细胞。卵粒的退化吸收分５步完成。     

艰难梭菌荚膜多糖单糖组成的气相色谱分析

本文对两株艰难梭菌（ＣｄＡ３１８和ＣｄＣＤＣ２７９）荚膜多糖进一步分析,结果证实纯化的艰难梭菌荚膜多糖为单一均匀的物质;经气相色谱分析表明,其单糖组分主要由Ｄ－葡萄糖、Ｄ－甘露糖和Ｄ－半乳糖组成,不同菌株的荚膜多糖可能有微小差异。     

新疆六个民族指纹白线的调查研究The hand Print of Six Nationalities in Xinjiang

本文首次报道了新家6各民族6134人（南3181人、女2953人）的指纹白线出现频率。结果表明,白线频率女高于男,民族间亦有差异,其中维吾尔、哈萨克、鸟孜别克族频率接近。塔吉克族居住高寒高原地区,属白色人种,频率明显低于以上3个民族,锡伯族和汉族生活习惯近似,且高于以上4个民族,作者认为,白线出现频率的高低与种族、性别、年龄和群体生长环境及生活习惯有关。We’ve studied 6134 individuals (male 3181, fimale 2953) of six nationalities in Xinjiang.The result is that the white line of hand print is associated with rae,sex,age,grow environments of groups and life habbits.The ifference of races is:The appearant rates of white line of Weivuerite,Hasakese and Wuzibese are near,Tajike’s rate is lower than xiboman’s and han are higher than others.     

Identification of residues of the H-ras protein critical for functional interaction with guanine nucleotide exchange factors.

Ras proteins are activated in vivo by guanine nucleotide exchange factors encoded by genes homologous to the CDC25 gene of Saccharomyces cerevisiae. We have taken a combined genetic and biochemical approach to probe the sites on Ras proteins important for interaction with such exchange factors and to further probe the mechanism of CDC25-catalyzed GDP-GTP exchange. Random mutagenesis coupled with genetic selection in S. cerevisiae was used to generate second-site mutations within human H-ras-ala15 which could suppress the ability of the Ala-15 substitution to block CDC25 function. We transferred these second-site suppressor mutations to normal H-ras and oncogenic H-rasVal-12 to test whether they induced a general loss of function or whether they selectively affected CDC25 interaction. Four highly selective mutations were discovered, and they affected the surface-located amino acid residues 62, 63, 67, and 69. Two lines of evidence suggested that these residues may be involved in binding to CDC25: (i) using the yeast two-hybrid system, we demonstrated that these mutants cannot bind CDC25 under conditions where the wild-type H-Ras protein can; (ii) we demonstrated that the binding to H-Ras of monoclonal antibody Y13-259, whose epitope has been mapped to residues 63, 65, 66, 67, 70, and 73, is blocked by the mouse sos1 and yeast CDC25 gene products. We also present evidence that the mechanism by which CDC25 catalyzes exchange is more involved than simply catalyzing the release of bound nucleotide and passively allowing nucleotides to rebind. Most critically, a complex of Ras and CDC25 protein, unlike free Fas protein, possesses significantly greater affinity for GTP than for GDP. Furthermore, the Ras CDC25 complex is more readily dissociated into free subunits by GTP than it is by GDP. Both of these results suggest a function for CDC25 in promoting the selective exchange of GTP for GDP.     

Functional and physical interaction between p53 and BZLF1: implications for Epstein-Barr virus latency.

The p53 tumor suppressor protein, which is commonly mutated in human cancers, has been shown to interact directly with virally encoded from papillomavirus, adenovirus, and simian virus 40. The disruption of p53 function may be required for efficient replication of certain viruses and may also play a role in the development of virally induced malignancies. Infection with Epstein-Barr virus (EBV) has been associated with the development of B-cell lymphomas and nasopharyngeal carcinoma. Here we show that the EBV immediate-early protein, BZLF1 (Z), which is responsible for initiating the switch from latent to lytic infection, can interact directly in vitro and in vivo with the tumor suppressor protein, p53. This interaction requires the coiled-coil dimerization domain of the Z protein and the carboxy-terminal portion of p53. Overexpression of wild-type p53 inhibits the ability of Z to disrupt viral latency. Likewise, Z inhibits p53-dependent transactivation in lymphoid cells. The direct interaction between Z and p53 may play a role in regulating the switch from latent to lytic viral infection.     

Suppression of albumin enhancer activity by H-ras and AP-1 in hepatocyte cell lines.

We demonstrated, using a transient transfection assay, that the albumin enhancer increased the expression of the albumin promoter in a highly differentiated, simian virus 40 (SV40)-immortalized hepatocyte cell line, CWSV1, but was not functional in two ras-transformed cell lines (NR3 and NR4) derived from CWSV1 by stable transfection with the T24ras oncogene. A transient cotransfection assay showed that T24ras and normal c-Ha-ras were each able to inhibit the activity of the albumin enhancer in an immortal hepatocyte cell line. DNase I footprinting and gel mobility shift assays demonstrated that the DNA binding activities specific to the albumin enhancer were not decreased in the ras-transformed cells. ras also did not diminish the expression of HNF1 alpha, C/EBP alpha, HNF3 alpha, HNF3 beta, or HNF3 gamma but did significantly increase AP-1 binding activity. Three AP-1 binding sites were identified within the albumin enhancer, and DNA binding activities specific to these AP-1 sites were induced in the ras-transformed hepatocytes. Subsequent functional assays showed that overexpression of c-jun and c-fos inhibited the activity of the albumin enhancer. Site-directed mutagenesis of the AP-1 binding sites in the albumin enhancer partially abrogated the suppressing effect of ras and c-jun/c-fos on the enhancer. These functional studies therefore supported the results of the structural studies with AP-1. We conclude that the activity of the albumin enhancer is subject to regulation by ras signaling pathways and that the effect of ras on the albumin enhancer activity may be mediated by AP-1.