Human CENP-H multimers colocalize with CENP-A and CENP-C at active centromere--kinetochore complexes

Centromere and kinetochore proteins have a pivotal role in centromere structure, kinetochore formation and sister chromatid separation. However, the molecular architecture and the precise dynamic function of the centromere-kinetochore complex during mitosis remain poorly understood. Here we report the isolation and characterization of human CENP-H. Confocal microscopic analyses of HeLa cells with anti-human CENP-H-specific antibody demonstrated that CENP-H colocalizes with inner kinetochore plate proteins CENP-A and CENP-C in both interphase and metaphase. CENP-H was present outside centromeric heterochromatin, where CENP-B is localized, and inside the kinetochore corona, where CENP-E is localized during prometaphase. Furthermore, CENP-H was detected at neocentromeres, but not at inactive centromeres in stable dicentric chromosomes. In vitro binding assays of human CENP-H with centromere-kinetochore proteins suggest that the CENP-H binds to itself and MCAK, but not to CENP-A, CENP-B or CENP-C. CENP-H multimers were observed in cells in which both FLAG-tagged CENP-H and hemagglutinin-tagged CENP-H were expressed. These results suggest that CENP-H multimers localize constitutively to the inner kinetochore plate and play an important fundamental role in organization and function of the active human centromere-kinetochore complex.     

Increased disulfide-mediated condensation of the nuclear DNA-protein complex in lymphocytes during postnatal development and aging

Previous studies with liver cells suggested that disulfide (SS) bonds may play a role in maintaining the compact structure of the condensed chromatin fraction in the interphase nucleus and in the formation of a more condensed nuclear DNA-protein complex with advancing age. In liver cells (generally postmitotic) the molecular species participating in these SS bonds appeared to be located in the relatively micrococcal nuclease resistant fraction of the nuclei. This fraction has been noted to contain a nuclear protein skeletal structure with which DNA associates. In the present study we investigated the SS mediated condensation of the nuclear DNA-protein complex in a non-postmitotic cell population (mouse spleen cells) as a function of postnatal development and aging, and the mechanism of the SS mediated condensation. The experiments involved lysis of live spleen cells on top of neutral sucrose gradients in the presence of varying concentrations of NaC1, or NaC1 plus varyingconcentrations of a positive supercoiler of DNA followed by sedimentation of nuclear DNA-protein complexes arising from these lyses. The results suggest that the SS mediated condensation of the nuclear DNA-protein complex previously found in liver cells may also occur in non-postmitotic (spleen) cells, and that it begins early in life and continues to increase during later aging. The molecular species participating in the SS bonds involved in the condensation appeared to be undissociable from DNA by 2.0 M NaC1, a concentration known to dissociate histones and most of the nonhistones from DNA, leaving behind a subgroup of nonhistone proteins. Studies by other workers have shown that such tightly DNA associated nonhistone proteins are largely homologous with the proteins of a nuclear protein skeletal structure obtained by extensive nucleolytic digestion of nuclei. Our present data are consistent with a role for SS bonds in the association of regions of nuclear DNA with the elements ofa nuclear protein skeletal structure. In addition we present evidence that a partial     

Chromatin compaction in terminally differentiated avian blood cells: the role of linker histone H5 and non-histone protein MENT

Chromatin has a tendency to shift from a relatively decondensed (active) to condensed (inactive) state during cell differentiation due to interactions of specific architectural and/or regulatory proteins with DNA. A promotion of chromatin folding in terminally differentiated avian blood cells requires the presence of either histone H5 in erythrocytes or non-histone protein, myeloid and erythroid nuclear termination stage-specific protein (MENT), in white blood cells (lymphocytes and granulocytes). These highly abundant proteins assist in folding of nucleosome arrays and self-association of chromatin fibers into compacted chromatin structures. Here, we briefly review structural aspects and molecular mode of action by which these unrelated proteins can spread condensed chromatin to form inactivated regions in the genome.     

Ultrastructure of the final nuclear maturation of bovine oocytes in vitro

Summary Cumulus-oocyte complexes were obtained from cow ovaries by aspiration from small (1–6 mm in diameter) antral follicles after slaughter. Complexes with a compact multilayered cumulus investment were cultured and subsequently processed for electron microscopy after various periods of culture. By morphological criteria the oocytes could be divided into the following sequence of meiotic stages. The oocyte nucleus I stage was characterized by a spherical nucleus located peripherally in the ooplasm while undulation of the nuclear envelope and initial chromatin condensation was seen at the oocyte nucleus II stage. The oocyte nucleus breakdown stage was characterized by formation of long slender projections from the nuclear envelope in which the envelope doubled back on itself, appearance of dense areas and haphazardly oriented microtubules in the nucleus, marked condensation of the chromatin, and dissolution of the nuclear envelope into irregular vesicles and tubules. The condensed chromatin I stage was characterized by the location of condensed chromatin configuration and uniformly oriented microtubules in a dense area peripherally in the ooplasm while the final condensed chromatin II stage was characterized by a gradual invasion of condensed chromatin configurations into a dense area combined with the presence of the first polar body in the perivitelline space.     

Blue native protein electrophoresis for studies of mouse polyomavirus morphogenesis and interactions between the major capsid protein VP1 and cellular proteins

Morphogenesis of the mouse polyomavirus virion is a complex and not yet well understood process. Nuclear lysates of infected cells and cells transiently producing the major capsid protein (VP1) of the mouse polyomavirus and whole-cell lysates were separated by blue native polyacrylamide gel electrophoresis (BN-PAGE) to characterize the participation of cellular proteins in virion precursor complexes. Several VP1-specific complexes were found by immunostaining with the anti-VP1 antibody. Some of these complexes contained proteins from the heat shock protein 70 family. The BN-PAGE was found to be a useful tool for the identification of protein complexes by immunostaining of separated cell lysates. However, whole-cell lysates and lysates of isolated nuclei of cells infected with polyomavirus appeared to be too complex for BN-PAGE separation followed by mass spectrometry. No distinct bands specific for cells infected with polyomavirus were detected by Coomassie blue stained gels, hence this method is not suitable for the discovery of new cellular proteins participating in virion assembly. Nevertheless, BN-PAGE can be valuable for the analyses of different types of complexes formed by proteins after their enrichment or isolation by affinity chromatography.     

The influence of B chromosomes on rDNA organization in rye interphase nuclei

Patterns of rye rDNA organization in interphase nuclei were studied through the use ofin situ hybridization in spreads of root meristem cells from plants with and without B chromosomes (Bs). In cells from plants without Bs each rDNA locus is organized as a single perinucleolar knob of condensed chromatin with decondensed chromatin inside the nucleolus. In plants with Bs there is a marked modification of the pattern, found in more than 23% of nuclei, which involves several regions of condensed chromatin interspersed with decondensed chromatin inside the nucleolus. This B-induced alteration in rDNA interphase organization suggests a change in expression of the rRNA genes located on the A chromosomes probably related to the reduction in nuclear RNA observed previously in plants with Bs. The influence of the Bs on the expression of A chromosome genes, through rearrangement of interphase chromatin, could provide the basis of an explanation for some of the known phenotypic effects of B chromosomes in rye.     

顺铂诱导人胃癌细胞SGC7901和人肝癌细胞HepG2凋亡的细胞形态学变化的比较

目的观察顺铂诱导人胃腺癌细胞SGC7901和人肝癌细胞HepG2细胞凋亡的细胞形态学的异同并探讨其意义。方法用倒置显微镜、荧光显微镜、透射电镜观察细胞经顺铂处理后的形态学改变。采用流式细胞术研究CDDP对两株肿瘤细胞诱导凋亡中DNA含量的影响。结果经顺铂处理后,两株肿瘤细胞均表现出一些共同的凋亡形态学特征,如细胞及细胞核皱缩,微绒毛消失,细胞膜皱缩但完整,细胞内荧光强度增强。细胞超微结构变化如线粒体肿胀,胞质空泡化。但两者在细胞核形态方面表现出较大的差异;SGC7901表现为核染色质呈团块状或环状,聚集于核膜下;而HepG2主要表现为核碎裂、核膜崩解,核染色质呈梅花状散落在细胞中和一些细胞器通过细胞出芽裂解成由细胞膜包绕的凋亡小体并被周围细胞吞噬。在两者的流式细胞DNA的直方图上均检测到了亚二倍体峰。结论顺铂可诱导SGC7901和HepG2产生不同形态的细胞凋亡,其中SGC7901主要表现为核固缩,HepG2表现为核碎裂。这种差异具有重要的生理意义。     

Computer assessment of chromatin patterns on some germ line cells of the hemipteran, Triatoma infestans Klug.

The digitized nuclear images of some Feulgen-stained primary and secondary spermatocytes of Triatoma infestans were analyzed with computer programs. Different cell types could be mathematically discriminated in terms of distance of the condensed chromatin areas from the center of the nucleus, relative circumference of these areas, and staining intensity ratio of the condensed chromatin areas with respect to the whole nucleus. The method appears promising for further comparative studies involving the whole spermatogenetic process of T. infestans. It is probably advantageous for the analysis of other hemipteran (and even non-hemipteran) spermatogeneses.     

Structural basis for targeting the chromatin repressor Sfmbt to Polycomb response elements

Polycomb group (PcG) protein complexes repress developmental regulator genes by modifying their chromatin. How different PcG proteins assemble into complexes and are recruited to their target genes is poorly understood. Here, we report the crystal structure of the core of the Drosophila PcG protein complex Pleiohomeotic (Pho)-repressive complex (PhoRC), which contains the Polycomb response element (PRE)-binding protein Pho and Sfmbt. The spacer region of Pho, separated from the DNA-binding domain by a long flexible linker, forms a tight complex with the four malignant brain tumor (4MBT) domain of Sfmbt. The highly conserved spacer region of the human Pho ortholog YY1 binds three of the four human 4MBT domain proteins in an analogous manner but with lower affinity. Comparison of the Drosophila Pho:Sfmbt and human YY1:MBTD1 complex structures provides a molecular explanation for the lower affinity of YY1 for human 4MBT domain proteins. Structure-guided mutations that disrupt the interaction between Pho and Sfmbt abolish formation of a ternary Sfmbt:Pho:DNA complex in vitro and repression of developmental regulator genes in Drosophila. PRE tethering of Sfmbt by Pho is therefore essential for Polycomb repression in Drosophila. Our results support a model where DNA tethering of Sfmbt by Pho and multivalent interactions of Sfmbt with histone modifications and other PcG proteins create a hub for PcG protein complex assembly at PREs.     

Identification and fine structure of proliferating hepatocytes in malignant and nonmalignant liver diseases by use of a monoclonal antibody against DNA polymerase alpha

To analyze the process of liver regeneration and the initiation of hepatocellular carcinoma (HCC), we studied histochemically the morphologic features of proliferating parenchymal cells stained for DNA polymerase alpha (DPA), in 31 patients with various diseases, by use of a monoclonal antibody against DPA. In specimens from patients with acute viral hepatitis with confluent necrosis, most stained hepatocytes were small, with basophilic cytoplasm, and were located next to the necrotic areas. Under electron microscopy, stained granules were seen in the nucleus. Most stained hepatocytes had immature organelles. In specimens from patients with cirrhosis of the liver, the number of stained hepatocytes greatly differed in different pseudolobules. In specimens from patients with adenomatous hyperplasia, stained hepatocytes, mostly small and basophilic, were found diffusely; electron microscopy showed slightly indented nuclei with a few organelles and less condensed chromatin than normal. In specimens from patients with HCC, most stained cancer cells were small and basophilic; electron microscopy showed indented nuclei with a few organelles and less than normal condensed chromatin. Staining showed that during regeneration, immature hepatocytes reentered the cell cycle and repaired a large necrotic area. It was conceivable that in the initiation of HCC, some small hepatocytes with indented nuclei and less condensed chromatin might become HCC cells.     

Double minutes in prematurely condensed chromatin of human tumor cells

Comparative studies on the occurrence of double minutes (DMs) were performed on metaphases and prematurely condensed interphases (G1, G2) of cells from 28 cancerous effusions of 24 carcinoma patients. In 21 of these effusions, agreement between metaphase and prematurely condensed chromatin (PCC) data was obtained concerning occurrence or nonoccurrence of DMs (10 DM positive, 11 DM negative). In two cases, DMs were observed in metaphases only, whereas in five cases, they were found in interphases only. In normal cells, no DMs could be found, neither in metaphase nor in PCC. No causal correlation of the occurrence of DMs and cytostatic therapy was found. The data suggest that cytogenetic screening of prematurely condensed interphase cells from human tumors or cancerous effusions provides a valuable method for estimating the incidence of gene amplification in malignant cells, particularly in those with poor mitotic yield.     

活性染色质诱导抗核抗体生成及肾损伤

系统性红斑狼疮 (SLE )的病因和诱导抗核抗体 (ANA )生成的激发原迄今不明。本实验试图用ConA活化淋巴细胞的染色质免疫同系BALB/c小鼠 ,寻找诱导ANA生成的真正免疫原 ,阐明SLE发生的激发原是自身活化细胞的核成分 ,而且证明它所诱导的ANA具有致病性。从ConA活化的脾细胞中提取染色质 ,然后免疫同系BALB/c小鼠 ,用ELISA方法测定IgG类抗双链DNA (dsDNA )、抗组蛋白抗体 ,用免疫荧光法检测抗核抗体核型和免疫复合物沉积 ,用免疫印迹法测定抗核抗体谱 ,在光镜下检测肾损伤及电镜下检测肾小球沉积物 ,用考马斯亮蓝法检测尿蛋白含量。结果显示 ,活性染色质能诱导IgG类抗dsDNA、抗组蛋白等多种抗核抗体生成 ,且肾小球有显著免疫复合物沉积和蛋白尿形成。该实验表明 ,活化淋巴细胞的染色质是诱导SLE发生的真正自身免疫原。     

Association of surface IgM with two membrane proteins on murine B lymphocytes detected by chemical crosslinking

Surface proteins of intact murine B lymphocytes were crosslinked by the bifunctional reagent, 4,4'-diphenyldiazoniumdisulphidfluoroborate and then radiolabelled with 125I. After solubilization of the cells, Ig-containing complexes (Ig and protein(s) covalently crosslinked to Ig) were isolated and analyzed by two-dimensional SDS polyacrylamide gel electrophoresis (2D-SDS-PAGE). Ig-containing complexes were separated in the first dimension by cylindrical SDS gels. Subsequently, the disulphide bridges of the isolated surface Ig molecules and of the crosslinking reagent were cleaved, and the products electrophoresed in the second dimension on SDS slab gels. In addition to the Ig polypeptide chains, two proteins with mol. wts of 46,000 and 56,000 could be identified. In order to answer the question whether these proteins are associated with IgM and/or IgD Ig-complexes were separated with regard to their isotype and analyzed separately by 2D-SDS-PAGE. It was found that both proteins are associated with subunits of IgM. In the case of IgD, no associated structures could be demonstrated by the method used.     

High-resolution localization of hyaluronic acid in the golden hamster oocyte-cumulus complex by use of a hyaluronidase-gold complex

The distribution of hyaluronic acid in the oocyte-cumulus complexes collected from the oviduct ampulla of superovulated hamsters was revealed by use of hyaluronidase coupled to colloidal gold. On thin sections of Lowicryl-embedded oocyte-cumulus complexes, gold particles were associated specifically with interconnecting fibrillar materials that make up the cumulus matrix. Inside the cumulus cells, gold particles were found over the cisternal membrane of the rough endoplasmic reticulum, in the contents of lysosomes and multivesicular bodies, and over Golgi vesicles of some cumulus cells. A high concentration of gold labeling was observed over the peripheral condensed chromatin and perinucleolar components in the nucleus. The cell surface of the cumulus cells also appeared to be labeled. Gold particles, however, were absent over the mitochondria and lipid vacuoles. In the oocytes, labeling was found to be associated mainly with rough endoplasmic reticulum and arrays of lamellar structures; cortical granules, mitochondria, and coated vesicles were essentially devoid of gold particles. Gold particles were also seen along the plasma membrane of the oocytes and within the perivitelline space. The zona pellucida was not labeled by hyaluronidase-gold. Different control experiments confirmed the specificity of the labeling. Digestion of thin sections with hyaluronidase prior to incubation with hyaluronidase-gold abolished the initial reaction, whereas treatment of thin sections with chondroitinase did not prevent labeling of oocyte-cumulus complexes by hyaluronidase-gold. Although the function of hyaluronic acid in the oocyte-cumulus complex at the time of ovulation and fertilization is not known, the high concentration of this particular compound in the cumulus matrix and the cumulus cells and its specific locations in the perivitelline space and in the superovulated oocytes implicate the significance of its presence and warrant future investigations.     

赤链蛇（Dinnodonrufozonatum）精子头部形成的电镜研究

为探讨赤链精子头产中形成及与其他动物的区别，用透射电镜观察赤链蛇精子形成过程中头部超微结构的主，中分成以下４个时期：时期Ⅰ，细胞核一端凹陷形成顶体囊泡、囊泡底部出现一顶体颗粒；时期Ⅱ，染色质纤维浓缩呈短丝状，顶体囊泡变扁平，顶体颗粒变大并弥散；时期Ⅲ，核进一步延长，染色质纤维进一步浓缩变长变粗。     

Differential glycosylation of MHC class II molecules on gastric epithelial cells: implications in local immune responses

Class II major histocompatibility complex (MHC) expression is a hallmark of antigen presenting cells (APC). Human gastric epithelial cells (GEC) express class II MHC and this expression increases during infection with Helicobacter pylori as does the number of CD4 T cells found adjacent or in between epithelial cells. These observations suggested that human GEC act as APCs. To characterize and compare class II MHC complexes with those present in conventional APC, immunoprecipitated class II MHC from GEC and B cells, as prototypic APC, were separated by two-dimensional electrophoresis. Although the composition of class II MHC from both cell phenotypes was similar, their electrophoretic mobility differed. Methodical elimination of carbohydrates, either enzymatically with endoglycosidase-H or blocking with tunicamycin, revealed that the deviations were due to differences in glycosylation in both cell phenotypes. When deglycosylated class II MHC alpha chains, beta chains, and the invariant chain from both cell phenotypes were mixed and run in the same gel, the core proteins had identical migration patterns. Because differences in glycosylation of class II MHC proteins may affect peptide selection and/or recognition by T cells, the noted differences in glycosylation of class II MHC expressed by GEC could be important in considering their potential role as APC locally.     

Dynamic relocation of telomere complexes in mouse meiotic chromosomes

Telomeric DNA repeats as well as different specific proteins such as TRF1 and Rap1 associate in functional telomere complexes found at chromosome ends. Using spreading techniques, the presence of TRF1 and Rap1 has been reported at mammalian meiotic telomeres during prophase I. In the present study, we have analysed, by fluorescence in-situ hybridization and immunofluorescence, the appearance and location of telomere complexes during both male mouse meiotic divisions. Additionally, we have studied their relationship with different centromere/kinetochore proteins and the synaptonemal complex protein SCP3. Our results show that telomere complexes are not located at condensed meiotic chromosome tips. Therefore, a change in chromosome structure may occur from pachytene up to metaphase I involving the dynamic relocation of telomere complexes in condensed chromosomes. Moreover, we have found that proximal telomere complexes are relocated internally to kinetochores from metaphase I up to anaphase II. We discuss the functional significance of the location of telomere complexes into internal domains of condensed meiotic chromosomes.     

Electron-microscopic investigation of satellite cell formation in skeletal muscle during physical exertion

The content of condensed chromatin is increased in nuclei of skeletal muscle fibers of rats after repeated physical exertion continued until exhaustion. Some muscle fiber nuclei, together with part of the sarcoplasm, were separated from the muscle fibers. Satellite cells formed from the separated parts of the muscle fibers.Laboratory of Functional Morphology, All-Union Scientific-Research Institute of Physical Culture, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Kupriyanov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1385–1388, November, 1976.     

Ultrastructure of the normal adult human female prostate gland (Skene’s gland)

The predominant cells of female prostatic glands lining their lumen were found to be tall cylindrical secretory cells with short stubby microvilli, protuberances of the apical cytoplasm, and with bleb formation. Abundant secretory vacuoles and granules, rough endoplasmic reticulum, developed Golgi complexes and numerous mitochondria are characteristic of their active secretory configuration with apocrine (apical blebs) and merocrine (secretory vacuoles and granules) type of secretion. Basal (reserve) cells were seen to be located between the secretory (luminal) cells and the basement membrane. Their ground cytoplasm is dense with rough endoplasmic reticulum and mitochondria. Their nuclei, unlike those of secretory cells, possess more peripheral condensed chromatin, denser dispersed chromatin and sporadic nucleoli. Besides the two basic types of mature prostatic cells intermediary cells were also seen, located between the basal and secretory cells or in their close vicinity. Their cytoplasm exhibits numerous profiles of rough endoplasmic reticulum and free ribosomes. Secretory vacuoles and granules were mostly practically absent (type 1 intermediary cells) so that they resembled basal (reserve) cells. In some of them, however, as in secretory cells, such secretory elements do gradually appear (type 2 intermediary cells). The finding of intermediary cells in the lining of prostatic glands supports the role of basal (reserve) cells in the renewal of cells in glands of the female prostate. The first ultrastructural analysis of the normal female prostate performed by transmission electron microscopy showed that, as in the postpubertal male, the prostatic glands in the adult female display mature secretory and basal cells. The results of the presented study further corroborate the contemporary concept of the female prostate as a functional genitourinary organ.