Biomedical subjects

L M Pabón-Peña

Publications and source records attributed to L M Pabón-Peña.

8 recordsLinked to original sources

PubMed2000

Analysis of CMF1 reveals a bone morphogenetic protein-independent component of the cardiomyogenic pathway.

Disruption of the CMF1 function in anterior mesoderm inhibits cardiac myogenesis in avian embryos. In the present study, we show that CMF1 is a member of an emerging family of proteins that includes centromeric protein-F, mitosin, and LEK1. These proteins are characterized by their large size (350 kDa), dynamic subcellular distribution, and potential functions in cell division and differentiation. The current data suggest that CMF1 is a unique member of this family by virtue of its restricted protein expression and variant subcellular distribution. Immunochemical analysis demonstrates that CMF1 protein is expressed in cardiogenic cells prior to the activation of cardiac structural gene products. In addition, we show that expression of CMF1 is not dependent on the bone morphogenetic protein (BMP) signaling pathway during development. Still, CMF1 cannot direct cardiomyogenesis in the absence of such factors as NKX-2.5. Taken with our previous data, this study suggests that CMF1 is a BMP-independent component of the cardiomyogenic pathway.

Amino Acid Sequence↗

PubMed2000

Characterization of CMF1 in avian skeletal muscle.

This study reports the identification of the CMF1 protein in somites and embryonic limb muscle. We have previously described CMF1 in developing cardiac muscle. CMF1 is a member of the LEK family of proteins, which are involved in regulating mitosis. Our current data suggest that CMF1 expressed in skeletal and cardiac myocytes is the product of a single gene and that the two proteins are homologous or very highly conserved. Immunohistochemistry shows a dynamic subcellular localization of CMF1 in differentiating skeletal myoblasts: Early myoblasts stain positively for CMF1 antigen in the nucleus, while differentiating myoblasts stain positively in the cytoplasm. CMF1 expression precedes myosin. Later, CMF1 and myosin are detected in the cytoplasm of the same cells. Transfection analysis identifies a functional nuclear localization signal (NLS) in CMF1, whose nuclear transport capability is modified by external sequences. To characterize the function of CMF1 in skeletal muscle, we used antisense oligonucleotides to disrupt CMF1 in myoblast cultures. Expression of CMF1 in early myotubes is reduced by an average of 40% on a cell by cell basis, with a 56% reduction in anti-myosin staining. These data suggest that CMF1 is involved in induction and/or accumulation of myosin in differentiating myocytes.

Amino Acid Sequence↗

PubMed2000

SSeCKS gene expression in vascular smooth muscle cells: regulation by angiotensin II and a potential role in the regulation of PAI-1 gene expression.

Rat aortic smooth muscle cells (RASM) express the src suppressed C-kinase substrate (SSeCKS), which is thought to be an integral regulatory component of cytoskeletal dynamics and G-protein coupled-receptor signaling modules. The specific sub-classes of growth factor receptors that regulate the genomic changes in SSeCKS expression in smooth muscle cells have not been characterized. In this study we identify SSeCKS as an angiotensin type 1 (AT(1)) receptor-dependent target gene in RASM cells treated with angiotensin II (Ang II). SSeCKS mRNA levels increase up to three-fold relative to the control within 3.5 h of Ang II treatment and are followed by a slight decrease of mRNA relative to the control levels after 24 h of stimulation. SSeCKS gene expression and plasminogen activator inhibitor-1 (PAI-1) gene expression correlate in RASM cells treated with Ang II. By co-transfecting plasmids bearing recombinant-SSeCKS and a PAI-1-promoter/luciferase reporter into Cos-1 cells, we show that alternative forms of recombinant-SSeCKS protein differentially influence PAI-1 promoter activity. These data indicate a biochemical linkage between SSeCKS activity and one or more of the cytoplasmic signaling pathways that are involved in the control of PAI-1 promoter activity. Finally, we show that the alternative forms of recombinant-SSeCKS protein differentially influence cell-spreading when ectopically expressed in ras -transformed rat kidney (KNRK) fibroblasts. Taken together, our data suggest that SSeCKS interacts with intracellular signaling pathways that control cytoskeletal remodeling and extracellular matrix remodeling following Ang II stimulation of the RASM cell.

A Kinase Anchor Proteins↗

PubMed1999

The cloning and analysis of LEK1 identifies variations in the LEK/centromere protein F/mitosin gene family.

We report the cloning of a novel murine cDNA, LEK1, that is related to human CENP-F and mitosin and more distantly to chicken CMF1. The proteins from these three organisms have significant homology, yet differ in their temporal, spatial, and subcellular localizations. The human proteins bind the kinetochore in mitotic cells, whereas the chicken protein is found only in skeletal and cardiac muscle and is developmentally regulated. Mouse LEK1 is a single copy gene that codes for two developmentally regulated transcripts. The LEK1 protein is expressed early and ubiquitously in mouse development and is generally down-regulated as development proceeds in a manner that correlates to a cessation of mitosis. In adult tissues, the LEK1 protein is detected exclusively in the pronucleus of the oocyte and was not observed in other actively dividing tissues. Subcellular localization revealed that the LEK1 protein in mitotic cells does not bind the kinetochore. From these data, we hypothesize that chicken CMF1, human CENP-F, mitosin, and mouse LEK1 are members of an emerging family of genes that have important and functionally distinct roles in development and cell division.

Amino Acid Sequence↗

PubMed1996

Novel requirements in peripheral structures of the extended satellite 2 hammerhead.

A number of RNAs that infect plants self-cleave using a domain called the hammerhead. The consensus plant hammerhead has three base paired stem structures. Stems I and III flank the cleaved phosphodiester and are connected to stem II by two unpaired and highly conserved sequences. We demonstrated previously that satellite 2 transcripts from the newt, Notophthalmus viridescens, use a modified hammerhead structure for self-cleavage. Here we show that hammerheads with similar modifications occur in satellite 2 from species representing two additional families of salamanders (Ambystoma talpoideum and Amphiuma tridactylum). The distinctive features of the modified satellite 2 hammerheads include unusually short stem III regions and internally looped extensions to stem I that are required for cleavage. However, despite the strict nucleotide requirement in the internal stem I loop of the newt hammerhead, the details of the stem I extensions differ in the three salamanders. An analysis of chimeric transcripts indicated that, in order for a specific stem I extension to be functional, it must be compatible with other regions of the modified satellite 2 hammerhead. One such region is stem II, and a mutational analysis has confirmed that there are specific sequence and/or structural requirements in stem II.

Animals↗

PubMed1993

Conserved sequence and functional domains in satellite 2 from three families of salamanders.

Thirteen satellite 2 elements from Ambystoma talpoideum and 16 from Amphiuma tridactylum were cloned, sequenced, and compared with the satellite 2 consensus from Notophthalmus viridescens. These elements have maintained a high degree of similarity during the 65-200 Myr that the salamander families, represented by the three species, have been separated. The DNA sequences of the consensus elements from A. talpoideum and A. tridactylum are 81% similar, and both are approximately 65% similar to the N. viridescens consensus. In addition to its DNA sequence, the functional properties of satellite 2 have also been conserved. By selecting and analyzing clones that closely mimicked the consensus of each species, we were able to demonstrate that satellite 2 from each species was capable of promoting transcription after injection into Xenopus laevis oocytes and that synthetic transcripts of satellite 2 from each species were capable of catalyzing their own site-specific cleavage. These properties may be related to the process of retroposition, which was previously proposed to be responsible for the genomic proliferation of satellite 2. Each of these functional properties also has general biological interest.

Ambystoma↗

PubMed1991

Alternative modes of self-cleavage by newt satellite 2 transcripts.

Synthetic transcripts of satellite 2 DNA from the newt undergo self-catalyzed cleavage in vitro. In this report we present evidence that there are at least two distinct modes of satellite 2 transcript self-cleavage. In one mode, a single cleavage domain folds into a structure which cleaves at a slow rate. This structure may be analogous to, or a variant of, the 'hammerhead' structure believed to be active during the self-cleavage of a number of infectious plant RNAs. In an alternative mode, multiple cleavage domains interact to cleave at an enhanced rate. The permutation of the repeated satellite 2 sequence determines which of these modes of cleavage will predominate, presumably by influencing the overall conformation of the RNA. We present a model for the self-processing of multimeric satellite 2 transcripts which incorporates both of these modes of self-cleavage.

Animals↗

PubMed1991

Newt satellite 2 transcripts self-cleave by using an extended hammerhead structure.

Synthetic transcripts of satellite 2 DNA from newts undergo self-catalyzed, site-specific cleavage in vitro. Cleavage occurs within a domain that is similar to the hammerhead domain used by a number of self-cleaving, infectious plant RNAs. The newt hammerhead has a potentially unstable structure due to a stem composed of two base pairs and a 2-nucleotide loop, and unlike other hammerheads that have been studied, it cannot cleave as an isolated unit. Here we show that cleavage by a single newt hammerhead requires additional satellite 2 sequences flanking both ends of the hammerhead domain. We also present a structural model of a truncated satellite 2 transcript which is capable of cleavage. The structure includes an internally looped extension to one of the conserved stems of the hammerhead. By in vitro mutagenesis, the identities of each of the five nucleotides composing one of the internal loops were shown to be critical for cleavage. Additional evidence that the extension stimulates self-cleavage in a manner other than by simply stabilizing the hammerhead is presented.

Animals↗