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Articles by Maria Carmo-Fonseca
Total Records ( 4 ) for Maria Carmo-Fonseca
  Jose Rino , Joana M. P. Desterro , Teresa R. Pacheco , Theodorus W. J. Gadella Jr. and Maria Carmo-Fonseca
  Splicing factors SF1 and U2AF associate cooperatively with pre-mRNA and play a crucial role in 3’ splice site recognition during early steps of spliceosome assembly. Formation of the active spliceosome subsequently displaces SF1 in a remodeling process that stabilizes the association of U2 snRNP with pre-mRNA. Fluorescence microscopy shows SF1 and U2AF distributed throughout the nucleoplasm, where transcription occurs, with additional concentration in nuclear speckles, where splicing factors accumulate when not engaged in splicing. Fluorescence recovery after photobleaching analysis in live cells shows that the mobilities of SF1 and the two subunits of U2AF (U2AF65 and U2AF35) are correlated with the abilities of these proteins to interact with each other. Direct binding of SF1 to U2AF65 was demonstrated by fluorescence resonance energy transfer in both the nucleoplasm and nuclear speckles. This interaction persisted after transcription inhibition, suggesting that SF1 associates with U2AF in a splicing-independent manner. We propose that SF1 and U2AF form extraspliceosomal complexes before and after taking part in the assembly of catalytic spliceosomes.
  Maria Carmo-Fonseca and Jose Francisco David-Ferreira
  Jose Francisco David-Ferreira is one of the most influential Professors of Cell and Developmental Biology in Portugal. David-Ferreira pioneered the use of electron microscopy in cell biology and experimental embryology. He also paved the way for successive generations of biologists who cross-fertilized the national scientific community. As we discuss briefly below, David-Ferreira is above all a Pedagogue and an Institution builder.
  Jose Rino , Jose Braga , Ricardo Henriques and Maria Carmo-Fonseca
  How we see organisms and cells depends on the tools at our disposal. For over 150 years, biologists were forced to rely on fixed, dehydrated and stained specimens in order to guess how the living cells could function. It all changed abruptly during the last two decades when the rapid development of novel imaging techniques revolutionized the way scientists look at the structures of life alive.
  Florian Heyd , Maria Carmo-Fonseca and Tarik Moroy
  The U2 auxiliary factor (U2AF) is an integral part of the spliceosome that is important for the recognition of the 3’ splice site. U2AF consists of a large and a small subunit, the prototypes of which are U2AF65 and U2AF35. Recent evidence suggests that several homologs of both U2AF subunits exist that are able to regulate alternative splicing. Here we have investigated the expression, intracellular localization, and nucleo-cytoplasmic shuttling of one homolog of the small U2AF subunit, U2AF26, and a splice variant lacking exon 7, U2AF26ΔE7. In contrast to the nuclear U2AF26, which displays active nucleo-cytoplasmic shuttling, U2AF26ΔE7 is localized in the cytoplasm. Our studies reveal a nuclear localization sequence in the C-terminal exons 7 and 8 of U2AF26 that differs from the known nuclear localization sequence in U2AF35. In addition, we could identify P32 as a protein that is able to interact with U2AF26 through this domain, and we demonstrate that this interaction is required for the nuclear translocation of U2AF26. Our results suggest the existence of two distinct nuclear import pathways for U2AF26 and U2AF35 that could independently control their intracellular distribution and availability to the splicing machinery. Such a mechanism could work in addition to the differential expression of U2AF homologs to contribute to the regulation of alternative splicing.
 
 
 
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