Dimeric configuration of SeqA protein bound to a pair of hemi-methylated GATC sequences

The binding of SeqA protein to hemi-methylated GATC sequences (hemi-sites) regulates chromosome initiation and the segregation of replicated chromosome in Escherichia coli. We have used atomic force microscopy to examine the architecture of SeqA and the mode of binding of one molecule of SeqA to a pair of hemi-sites in aqueous solution. SeqA has a bipartite structure composed of a large and a small lobe. Upon binding of a SeqA molecule to a pair of hemi-sites, the larger lobe becomes visibly separated into two DNA binding domains, each of which binds to one hemi-site. The two DNA binding domains are held together by association between the two multimerization domains that make up the smaller lobe. The binding of each DNA binding domain to a hemi-site leads to bending of the bound DNA inwards toward the bound protein. In this way, SeqA adopts a dimeric configuration when bound to a pair of hemi-sites. Mutational analysis of the multimerization domain indicates that, in addition to multimerization of SeqA polypeptides, this domain contributes to the ability of SeqA to bind to a pair of hemi-sites and to its cooperative behavior

Csm4, in Collaboration with Ndj1, Mediates Telomere-Led Chromosome Dynamics and Recombination during Yeast Meiosis

Chromosome movements are a general feature of mid-prophase of meiosis. In budding yeast, meiotic chromosomes exhibit dynamic movements, led by nuclear envelope (NE)-associated telomeres, throughout the zygotene and pachytene stages. Zygotene motion underlies the global tendency for colocalization of NE-associated chromosome ends in a “bouquet.” In this study, we identify Csm4 as a new molecular participant in these processes and show that, unlike the two previously identified components, Ndj1 and Mps3, Csm4 is not required for meiosis-specific telomere/NE association. Instead, it acts to couple telomere/NE ensembles to a force generation mechanism. Mutants lacking Csm4 and/or Ndj1 display the following closely related phenotypes: (i) elevated crossover (CO) frequencies and decreased CO interference without abrogation of normal pathways; (ii) delayed progression of recombination, and recombination-coupled chromosome morphogenesis, with resulting delays in the MI division; and (iii) nondisjunction of homologs at the MI division for some reason other than absence of (the obligatory) CO(s). The recombination effects are discussed in the context of a model where the underlying defect is chromosome movement, the absence of which results in persistence of inappropriate chromosome relationships that, in turn, results in the observed mutant phenotypes

BA Degree Programme in Social Sciences

Lateral pharyngeal space (LPS), also called parapharyngeal space (PPS), is one of the important fascial planes of the head and neck, that may become involved by various pathological processes, such as infections, inflammation and neoplasms.1 This space is well known to the oral and maxillofacial surgeons as the area of spreading dental infection, where incision and drainage becomes necessary for keeping absolute respiration and airway, and also as the most difficult space to approach because of the many different kinds of muscles, fascias, vessels and nerves. The calcified stylohyoid ligament with styloid process is also located in this space, so this space is more acquainted with Eagles syndrome to the maxillofacial and plastic surgeons

metastatic leiomyosacroma

Leiomyosarcoma (LMS) is a relatively uncommon malignant tumour derived from smooth muscle cells that rapidly metastasizes to distant regions. It rarely reaches oral tissues in which smooth muscle tissues are absent. We report the case of a 56-year-old woman who presented with LMS in the maxilla that had metastasized from a primary tumour in her uterus, received a total hysterectomy with bilateral salpingo–oophorectomy 9 months earlier. To reveal the poor prognosis of metastatic LMS, a total of 26 antibodies against different factors related to the proliferation, apoptosis, necrosis, and angiogenesis were simultaneously applied on the immunohistochemistry and immuno-blot detection in order to screen for expression n of different proteins in the metastatic LMS. Compared with the immunoreactions of primary uterine LMS, the different antibodies for cellular proliferation, i.e., proliferating cell nuclear antigen (PCNA), multiple primary neoplasm-2 (MPN-2), Max, p21, CDK4, p53, Rb-1, Bad, Bcl-2, epidermal growth factor receptor (EGF-R), hepatocyte growth factor (HGF), C-erbb2, Maspin, and DMBT-1, and those for angiogenesis, i.e., vWF, CD31, and Angiogenin, were more intensely expressed, while Bax, p16, Wnt-1, E-cadherin, and APC were relatively weakly expressed. In particular, beta-catenin was densely localized to the nuclei of tumour cells. These data suggest that rapid proliferation of the tumour cells is related to over-expression of different oncogenes, and that the infiltrative growth and early distant metastasis of these tumour cells are related to over-expression of angiogenesis factors. A total of seven cases of metastatic LMS to the oral cavity that had been published in the English literature were reviewed, and the reason for the poor prognosis in the metastatic LMS is suggested in this case report.This work was supported by the Korea Research Foundation Grant funded by the Korean government (MOEHRD, Basic Research Promotion Fund) (KRF- 2009-R1A4A002-0075286)

Crystallization and preliminary X-ray crystallographic studies of response regulator for cyanobacterial phytochrome, Rcp1

The key response-regulator gene of light regulation, rcp1, from Synechocystis sp. has been overexpressed, purified and subsequently crystallized using ammonium sulfate as a precipitant in forms suitable for X-ray crystallographic studies. A native data set was collected to a resolution of 2.5 Angstrom at cryogenic temperature. The crystals belong to the hexagonal space group P6(3), with unit-cell parameters a = b = 89.04 (5), c = 60.29 (3) Angstrom. The Matthews parameter suggests that Rcp1 crystallizes with two molecules per asymmetric unit