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Biomedical subjects

C E Peña

Publications and source records attributed to C E Peña.

At least 19 recordsLinked to original sources
PubMed2000

Assembly and activation of site-specific recombination complexes.

Site-specific recombination is responsible for a broad range of biological phenomena, including DNA inversion, resolution of transposition intermediates, and the integration and excision of bacteriophage genomes. Integration of mycobacteriophage L5 is catalyzed by a phage-encoded integrase with recombination occurring between specific attachment sites on the phage and mycobacterial chromosomes (attP and attB, respectively). Although some site-specific recombination systems simply involve binding of the recombinase to the sites of strand exchange, synapsis, and recombination, phage systems typically require the assembly of higher-order structures within which the recombinational potential of integrase is activated. The requirement for these structures derives from the necessity to regulate the directionality of recombination-either integration or excision-which must be closely coordinated with other aspects of the phage growth cycles. We show herein that there are multiple pathways available for the assembly of L5 recombination complexes, including the early synapsis of the attP and attB DNAs. This process is in contrast to the model for lambda integration and illustrates the different usage of molecular machineries to accomplish the same biological outcome.

DNA, Bacterial↗
PubMed1999

Protein-DNA complexes in mycobacteriophage L5 integrative recombination.

The temperate mycobacteriophage L5 integrates site specifically into the genomes of Mycobacterium smegmatis, Mycobacterium tuberculosis, and Mycobacterium bovis bacillus Calmette-Guérin. This integrative recombination event occurs between the phage L5 attP site and the mycobacterial attB site and requires the phage-encoded integrase and mycobacterial-encoded integration host factor mIHF. Here we show that attP, Int-L5, and mIHF assemble into a recombinationally active complex, the intasome, which is capable of attB capture and formation of products. The arm-type integrase binding sites within attP play specialized roles in the formation of specific protein-DNA architectures; the intasome is constructed by the formation of intramolecular integrase bridges between one pair of sites, P4-P5, and the attP core, while an additional pair of sites, P1-P2, is required for interaction with attB.

Base Sequence↗
PubMed1998

Mycobacteriophage D29 integrase-mediated recombination: specificity of mycobacteriophage integration.

Mycobacteriophage D29 is a lytic phage that infects both fast- and slow-growing species of the mycobacteria. D29 forms clear plaques on lawns of Mycobacterium smegmatis and Mycobacterium bovis bacille Calmette-Guérin (BCG) in which a very high proportion of infected cells are killed. However, genomic analysis of D29 demonstrates that it is a close relative of the temperate mycobacteriophage L5, and is presumably a non-temperate derivative of a temperate parent. The D29 genome encodes a putative integrase protein with a primary amino acid sequence similar to that of the L5 integrase; the corresponding int genes fall in colinear positions within the D29 and L5 genomes, immediately flanking and transcribed away from their associated attP sites. We show here that the D29 integrase is functional and catalyzes integrative recombination between the D29 attP site and the M. smegmatis attB site in vitro in an mIHF-dependent manner. D29 integrase also mediates recombination between the L5 attP site and attB DNA and, reciprocally, L5 integrase catalyzes recombination with D29 attP DNA. However, in both in-vitro and in-vivo assays, the D29-encoded integrase recombines the D29 attP more efficiently than the L5 attP, and vice versa, suggesting that each integration system has evolved a degree of specificity of attP recognition. We also present the sequences of the putative attP site and integrase protein of the cryptic prophage-like element phiRv2, and compare them to those of mycobacteriophages L5 and D29.

Amino Acid Sequence↗
PubMed1998

The role of supercoiling in mycobacteriophage L5 integrative recombination.

The genome of temperate mycobacteriophage L5 integrates into the chromosomes of its hosts, including Mycobacterium smegmatis , Mycobacterium tuberculosis and bacille Calmette-Guérin. This integrase-mediated site-specific recombination reaction occurs between the phage attP site and the mycobacterial attB site and requires the mycobacterial integration host factor. Here we examine the role of supercoiling in this reaction and show that integration is stimulated by DNA supercoiling but that supercoiling of either the attP or the attB substrate enhances recombination. Supercoiling thus facilitates a post-synaptic recombination event. We also show that, while supercoiling is not required for the production of a recombinagenic intasome, a mutant attP DNA deficient in binding of the host factor acquires a dependence on supercoiling for intasome formation and recombination.

Bacterial Proteins↗
PubMed1997

Characterization of the mycobacteriophage L5 attachment site, attP.

Lysogenization of mycobacteriophage L5 involves integration of the phage genome into the Mycobacterium smegmatis chromosome. Integration occurs by a site-specific recombination event between a phage attachment site, attP, and a bacterial attachment site, attB, which is catalyzed by the phage-encoded integrase protein. DNase I footprinting reveals that L5 integrase binds to two types of sites within attP which span an unexpectedly large region of 413 bp: seven arm-type sites (P1 to P7) each of which correspond to a consensus sequence 5'-TGCaaCtcYy, and core-type sites at the points of strand exchange. Mutational analyses indicate that not all of the arm-type sites are required for integration, and that the P3 site and the rightmost pair of sites (P6 and P7) are dispensable for integration. We show that a 252 bp segment of attP DNA is sufficient for efficient integrative recombination and that int can be provided in trans for simple and efficient transformation of the mycobacteria.

Bacteriophages↗
PubMed1996

Positions of strand exchange in mycobacteriophage L5 integration and characterization of the attB site.

Mycobacteriophage L5 integrates into the genome of Mycobacterium smegmatis via site-specific recombination between the phage attP site and the bacterial attB site. These two sites have a 43-bp common core sequence within which strand exchange occurs and which overlaps a tRNAGly gene at attB. We show here that a 29-bp segment of DNA is necessary and sufficient for attB function and identify the positions of strand exchange.

Anticodon↗
PubMed1989

Intracytoplasmic eosinophilic inclusions in the neurons of the central nervous system.

This study reports the histological, ultrastructural, and immunocytochemical characteristics of intracytoplasmic eosinophilic inclusion bodies occurring in various types of neurons of the human central nervous system. By light microscopy, the inclusions were brightly eosinophilic, slightly birefringent, and sharply demarcated; they were found in the thalamus in 92% of the cases, in the substantia nigra in 88%, in the locus coeruleus in 45%, and rarely in the spinal cord. Ultrastructurally, the inclusions were composed of assemblies of parallel, alternating dark and light rectilinear profiles. The dark profiles corresponded to thin filaments (microfilaments) that measured 5.5-6.0 nm in diameter. A second set of dense lines crisscrossed the first at right angles. In sections perpendicular to their long axis, the filaments were distributed in a tetragonal lattice pattern in which individual elements occupied the angles of a square. Immunocytochemical preparations for actin were negative. Due to their high rate of occurrence in nonpathological brains, it is thought that the inclusions represent a normal but as yet unidentified cytoplasmic organelle.

Adult↗
PubMed1983

Mixed capillary hemangioblastoma and glioma. A redefinition of the "angioglioma".

The histopathologic features of four cases of mixed capillary hemangioblastoma and glioma are described. In three cases, two of which arose in the cerebellum and one in the spinal cord, the hemangioblastic component may have originated from a neoplastic proliferation of the exuberant vascular stroma in a glial tumor. In a fourth case, a cerebellar hemangioblastoma was surrounded by a peripheral rim of atypical neoplastic-looking astrocytes ("reactive glioma"). The controversial concept of the "angioglioma" is reviewed, and it is proposed that the term be used to designate only true mixed tumors of glial and vascular tissue origin whose histologic features conform to the examples described in this report.

Aged↗
PubMed1980

Periodic units in the intracristal and envelope spaces of neuronal mitochondria. An artifact due to delayed fixation.

Ultrastructural study of the cerebral cortex and spinal anterior horns disclosed periodically repeating processes located in the envelope space or in the intracristal space of neuronal mitochondria. The alteration was observed in postmortem cases in which fixation was delayed either voluntarily or involuntarily, but was not present in postmortem or surgical specimens in which fixation was prompt. The change is interpreted as an artifact due to delayed fixation.

Cerebral Cortex↗
PubMed1980

Intracytoplasmic neuronal inclusions in the human thalamus. Light-microscopic, histochemical, and ultrastructural observations.

Intracytoplasmic eosinophilic inclusions were found by light microscopy in the thalamic neurons of 35 consecutive normal adult brains and in a case of myotonic dystrophy, but not in six newborn children, including one with myotonic dystrophy. Histochemical tests suggested a protein composition. Ultrastructurally, the inclusions were composed of stacks of parallel alternating dark and light rectilinear profiles not surrounded by a limiting membrane. Such inclusions are a virtually constant finding in the adult human thalamus and probably represent sites of neuronal protein storage.

Adult↗
PubMed1978

Ribosome-submembranous density complex. A new specialized cell unit.

Ultrastructural study of a malignant meningioma revealed an organelle complex composed of: (1) A band-like densification of the cell cytoplasm adjacent to and in contact with the cell membrane. (2) An arciform filament immediately subjacent to it, with concavity directed away from the cell membrane. (3) A row of regularly spaced ribosomes located in the concavity, but at some distance from the arciform filament. (4) A pericellular condensation of interstitial ground substance. Occasionally, a second, thinner filament was seen "threading" the ribosomes together. Its morphology was consistent with that described for messenger RNA . It is suggested that the ribosomes are engaged in the synthesis of proteins for other portions of the organelle complex and that the ultimate role of the specialized unit would be that of an attachment device.

Cell Membrane↗
PubMed1977

Meningioma and intracranial hemangiopericytoma. A comparative electron microscopic study.

Electron microscopic study of 2 intracranial hemangiopericytomas and 7 meningiomas revealed fundamental morphologic differences between the 2 neoplasms. The most significant finding in hemangiopericytoma was the presence of ultrastructure features suggesting leiomyoblastic differentiation. These included characteristic fusiform intracytoplasmic and submembranous dense bodies, abundant cytoplasmic filaments, elongated cells with blunt-ended nuclei and juxtanuclear polarization of organelles. This observation is considered highly significant as an indicator of the pericytic nature of this tumor. In addition, hemangiopericytoma cells sometimes were arranged in spirals around pools of basement membrane-like material, perhaps a manifestation of the biologic capability of the cells to synthetize such material. Meningioma cells displayed as their main feature an ability to produce surface membrane specializations including interdigitations, desmosomes, zonulae adhaerentes and gap functions. Sometimes the last 3 elements were linearly juxtaposed forming junctional complexes similar to those seen in certain epithelia. It is suggested that the characteristic whorls of meningioma are the result of cell interconnections arising from the specialized junctional attachments. Thus the distinctive morphology of the 2 neoplasms appears to derive from basic biologic properties of their elements.

Basement Membrane↗
PubMed1977

Lymphomatoid granulomatosis with cerebral involvement. Light and electron microscopic study of a case.

Light and EM study of a case of lymphomatoid granulomatosis revealed a pleomorphic lymphoreticular cell infiltrate, angitis and necrosis with involvement of the brain, lungs, skin and right ear of a 30 year old woman. Cells comprising the infiltrate were classified as lymphocytoid, plasmacytoid, immunoblastic (histocytic) and phagocytic. A number of elements partook of the ultrastructural features of two cell types and were considered to be intermediate forms (plasmacytoid lymphocytes, lymphocytoid immunoblasts, and plasmacytoid immunoblasts). It is believed that the various cell elements form part of a wide spectrum in which transformation of cell types takes place by maturation. This suggests an immunologic process as the main pathogenetic factor in the development of LG.

Adult↗
PubMed1975

Intracranial hemangiopericytoma: ultrastructural evidence of its leiomyoblastic differentiation.

Two intracranial hemangiopericytomas revealed subcellular features of the neoplastic elements comparable to those observed in normal and neoplastic smooth muscle. These included intracytoplasmic and submembranous fusiform dense bodies associated with bundles of filaments, tapered configuration of cells with grouping of cytoplasmic organelles at nuclear poles and deposition of intercellular basal lamina-like material. These observations are consistent with the pericytic origin but opposed to the ofttimes postulated meningothelial derivation of the neoplasm.

Basement Membrane↗